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Mahmoud, Mohamad. "Design, Fabrication, and Characterization of Monolithically Integrated Acoustic and Photonic Devices on Lithium Niobate Over Insulator (LNOI) Platform." Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1133.
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Integration of acoustics and photonics devices on the same chip will enable various applications including: building miniaturized sensors, on-chip filtering and optical signal processing, high speed modulation, as well as non-linear optical devices. As an example of the capabilities enabled by such integration, we target the development of a rotation sensor gyroscope based on the acousto-optic effect. The gyroscope components are integrated on a Lithium Niobate Over Insulator (LNOI) substrate because it is a unique platform that exhibits exceptional acoustic as well as photonic properties. However, acoustics and photonics have never been integrated on such substrate, which required the development of a new fabrication process and the design of novel components.. The main challenges we had to overcome and resulted in innovative demonstrations of fabrication processes and devices are: Developing a robust fabrication process for etching lithium Niobate (LN) waveguides and integrating them with acoustic transducers: A robust fabrication process was developed on the LNOI platform, which can integrate patterning sub-micron features together with microscale ones on the same 3’’ substrate. Furthermore, the developed fabrication process enabled integrating metallic Al electrodes together with etched LN waveguides, which is required for building various components like electro-optic modulators and acousto-optic modulators. Coupling light in and out of chip: Gratings couplers were designed for optimum coupling of the TE polarized light. The optimization was based on FDTD simulation on LUMERICAL. The grating couplers realization enabled estimation of the light coupling loss in and out of the chip. The measured coupling loss was about 9 dB per coupler in the best case which is much more than the estimated from simulation. That difference is attributed to the alignment accuracy of the photonic chip. Integrating photonic waveguides/resonators and coupling light between them: LNOI waveguides and photonic resonators were designed and built. The photonic resonators enabled extraction of the losses of waveguides by monitoring the photonic resonator Quality factor, Q, or Finesse (F). Directional couplers (DCs) are commonly used as coupling elements to photonic resonators. However, etching narrow gaps in LN is a challenge that we avoided by using multi-mode interference (MMI) couplers, where butterfly MMI couplers were designed as coupling element to photonic racetrack (RT) resonators aiming for critical coupling condition. Additionally 3-dB MMI couplers were designed to be used as beam combiners in the Mach-Zehnder interferometer (MZI). The built RT resonators enabled extraction of the propagation losses in the etched LNOI photonic waveguides, which were found to be equal to2.5 dB/cm. Building high efficiency electro-optic modulators (EOMs): The EOM is used in the AOG to compensate for temperature variations and other environmental variation affecting the rotation measurement. The EOM realization enabled extraction of the electro-optic (EO) coefficient for the LN thin film, which permits to evaluate the magnitude of the control voltages required to stabilize the system. EOMs of two different types were demonstrated, one is based on a photonic RT while the other is based on an Asymmetric MZI (AMZI). The RT EOM represents the first demonstration for such device with etched waveguides in Y cut LNOI platform. Modulation bandwidth of 4 GHz, wavelength tuning rate of 0.32 pm/V and an ER of more than 10 dB were experimentally measured for the RT EOM. For the AMZI, a half wave voltage length product of 16.8 Vcm was experimentally measured. Although, it is not the best we can get from this LNOI platform because of our wide waveguides, feeding that EO coefficient to the AOG system model ensures that the temperature variation from -54 oC to 25 oC can be compensated by applying a maximum voltage of 64.5 V. Building efficient acousto-optic modulators (AOMs): The AOM enabled the extraction of the acousto-optic (AO) coefficient, which directly impacts the AOG scale factor (SF). Additionally, two different types of AOMs were demonstrated, one is based on an MZI embedded inside a SAW cavity while the other is based on a photonic RT whose coupling condition is under EO control. For the MZI AOM, the SAW resonator enhances the modulation efficiency due to the resonator Q such that the phase shift per square root of power extracted from the measurements is a factor of 3x higher than what previously reported on a GaAs platform, which makes it, to the author’s knowledge, effectively the highest AO modulation ever attained on chip. On the other hand, the EO tuned RT AOM showcases integration of various functionalities on same platform to build efficient AOM that can be operated at the desired wavelength. The EO tuning not only changes the operating optical wavelength but also ensures the critical coupling condition needed for efficient modulation. This design takes advantage of the unique AO and EO properties of LN, hence showcasing important building blocks for RF-photonic applications. By addressing all the previous challenges through the demonstration of high performance components, we were able to prototype the first acousto-optic gyroscope. That prototype represents the first demonstration of a novel rotation sensing technique, which combines the following advantages: (i) large mass (there is no suspended mass in the sensing mechanism and hence no limits on increasing the mass and no concerns about stiction issues during fabrication), and (ii) high shock resistance (since the sensing mechanism is strain based, the AOG has no moving parts that would not survive high G accelerations). The AOG SF is estimated comparing three photonic phase sensing techniques which are MZI, RT as well as RT coupled to MZI (MZI/RT). The phase sensitivity is estimated in terms of the cavity F for each technique. That theoretical analysis is verified by experimental measurement for the SF for both the MZI and the RT AOGs. The measured SF for the MZI is 48 nv/(o/sec) while it is about 9 nv/(o/sec) for the RT AOG. The SF is lower for the RT AOG because the Finesse (F~6) of the RT is not as high as expected. Nevertheless, these prototypes represent a proof of concept for our novel method for sensing rotation. Future work could prove that this AOG concept could be disruptive. Reducing the losses in the LNOI waveguide is a key challenge that can be overcome and has been already demonstrated by other groups showcasing 100x lower propagation loss. The estimated F from our model in that case would increase by approximately 50x, hence improving the gyroscope SF by the same factor. Further improvement of 100x is possible by increasing the SAW wavelength and Q. A separate challenge that needs to be addressed is the laser and photodetector integration on chip, which will reduce the coupling loss and the sensitivity to optical alignment.
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Bonneau, Damien. "Integrated quantum photonics at telecommunication wavelength in silicon-on-insulator and lithium niobate platforms." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664624.
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Photonic quantum technologies are a promising approach to implement quantum information tasks including physically secured communication, efficient simulation of quantum systems, and could ultimately lead to the realisation of a full scale quantum computer. Integrated photonics have been successfully used to expand the scope of quantum optics experiments, unlocking the capability to perform more and more complex quantum tasks. The current effort points towards the integration of all the components in a single monolithic chip including single photon sources, passive circuits, fast phase-modulators, single photon detectors and electronics. Following this goal, we present technological steps towards further integration. We first show fast manipulation of single and two-photon states in an integrated lithium niobate circuit. We then move to the silicon-on-insulator platform providing orders of magnitude more compact circuits. We demonstrate the operation of several key components in the quantum regime, including quantum interference in a passive integrated multimode coupler, manipulation of quantum states using a reconfigurable phase-shifter in a Mach-Zehnder interferometer, and on-chip production of photon pairs. Engineering considerations are discussed for different components, including a study of the optimal parameter space for resonant photon pair sources. We then demonstrate the combined operation in a single chip of two photon pair sources together with passive circuitry and a phase-shifter, and show high visibility on the resulting quantum interference fringes. Then, considering state of the art technologies, including results from this work, we study several multiplexed schemes for implementing a crucially missing building block so far: a near-deterministic single photon source.
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Barry, Ian Eric. "Microstructuring of lithium niobate." Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/15498/.
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This thesis presents the results from an investigation into methods for micron-scale relief structuring of lithium niobate. A wet etch consisting of HF and HNO3 was applied, and directed by 1) patterning the ferroelectric domain structure of the samples and 2) illuminating the crystals with patterned 488nm light. Post-etch treatment of the structures resulted in ridge waveguides and alignment grooves, while pre-etch manipulation achieved an etch-stop. Ablation was investigated as a method of directly structuring the crystal and for patterning photoresist. The etch was found to leave the +z face untouched. The -z face was etched at a rate, k, in µm/hour given by k = e 20.37 - 6300/T where T is the absolute temperature. This differential etch rate reveals a pattern induced in the ferroelectric domain structure by the technique of electric field patterning. The structures had walls with roughness < 5nm. Straight walls were easily achieved aligned along the y-direction at 120o to this. Other directions can result in facetted walls. Ridge waveguide losses <1dBcm-1, fibre alignment grooves and an etch stop were demonstrated using appropriate pre- and post-etch treatments. The etch was found to be affected by illumination with 488nm radiation. In Fe:LiNbO3 complete and partial frustration of the etch was induced on the -z face. Characteristic features of the partial frustration were sub-micron ridges and triangular pillars, separated by gaps as small as 500nm. In LiNbO3 the etch rate was found to increase on the -z face. The etch rate on the +z face was unaffected in both. Direct ablation with an excimer laser produced relief structures. Aspect ratios > 1:1 resulted in a dendritic structure in the ablated area. Direct ablation was suitable for patterning the photoresist. Surface damage was intentionally induced when producing large (>100µm) openings, however, the effect of surface damage on electric field poling could not be conclusively tested. Submicron openings were also created and subsequent poling produced sub-micron domains, revealed by etching.
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Jaeger, Nicolas August Fleming. "Integrated optical devices in lithium niobate." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/26300.
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A class of integrated optical devices is based on light propagation in optical channel waveguides. It includes optical modulators such as the integrated Mach-Zehnder (IMZ). Many applications have been proposed for such integrated optical devices. The present work was motivated by a proposed application to voltage determination on high voltage lines, for example, SF₆ bus ducts in Hydro substations. For the voltage measurement application two device types were proposed. The first includes devices using capacitive voltage dividers. A novel divider for the SF₆ bus duct application was proposed using a LiNbO₃ wafer into which an IMZ could be built to give an integrated unit. Time permitted the divider to be tested only using a separate IMZ. The second type of device includes Immersion devices. Two novel immersion devices are proposed and their theory is developed. IMZs were made for the demonstrated, high voltage sensor, by diffusing Ti into LiNbO₃. Much effort was put into solving a sequence of experimental obstacles including the elimination of Li₂O out-diffusion (which causes a waveguide to be produced on the whole surface), the polishing of the LiNbO₃ crystals and optical fibers, and the butt coupling of the fibers to the crystals. In the end IMZs were fabricated with state-of-the-art extinction ratios. A third device, employing voltage induced waveguides, was proposed and was demonstrated. A mathematical treatment of the theory of the IMZ is provided.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Wessel, Rudolf. "Modelocked waveguide lasers in lithium niobate /." Paderborn : HNI, 2000. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=008936815&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Jorgensen, Jonathan David. "Electon paramagnetic resonance of lithium niobate heavily doped with chromium and lithium niobate codoped with magnesium and iron." Thesis, Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/jorgensen/JorgensenJ0810.pdf.
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In this thesis, electron paramagnetic resonance (EPR) was utilized in measuring and characterizing the dopant ions in three samples of lithium niobate (LiNbO₃). The first sample was LiNbO₃ of congruent composition doped with 0.25% mol chromium (LiNbO₃:Cr). This sample was studied in detail using two microwave frequencies, 9.4 GHz and 34.4 GHz. It was also studied both at room temperature and at 10 K. Several centers including complexes of Cr-Cr pairs were observed in addition to the most prevalent axial Cr³⺠center. The other two samples were LiNbO₃:Mg:Fe, one of congruent composition and the other of stoichiometric composition. The congruent composition contained 6% mol Mg and 0.02% mol Fe, while the stoichiometric sample contained 0.45% mol Mg and 0.01% mol Fe. The stoichiometric composition contains all the same centers observed in the congruent material, plus two additional centers. Since the stoichiometric material provides EPR spectra of much higher resolution, those centers existing in both compositions were characterized more accurately from the stoichiometric material. A discussion of models for dopant center symmetries, dopant positions in the LiNbO₃ lattice, and the charge compensators required by each center is provided. It is shown that charge compensators play an important role in explaining the existence of the additional centers observed in the stoichiometric material.
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Mohamedelhassan, Ashraf. "Fabrication of Ridge Waveguides in Lithium Niobate." Thesis, KTH, Fysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95360.
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Harun, Ahmad Mukifza. "Treparation of lithium niobate nanocrystals and nanocomposites." Thesis, University of Leeds, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595647.
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The rapid advancement in electronic industries is driven by variety in electronic and electrical miniaturization concept design. Enhancement in performance, for example better scaling, stable response, less performance fatigue and miniaturization is at the heart or global research interest. Consistent with this concept, this research targets the development of a ferroelectric composite comprising inorganic ferroelectric and ferroelectric polymer, with potential for applications as the gate in ferroelectric fielq effect transistors. The inorganic ferroelectric material in this research was lithium niobate. Lithium niobate is known to have a high Curie temperature and low permittivity value. Even though lithium niobate (LiNbO3) possesses very good ferroelectric properties there are relatively few instances in which these properties are exploited in terms of composites. nus first research stage was to investigate the preparation of LiNb03 nanocrystals for use in a thin film nanocomposite. This stage describes the preparation and characterization of LiNbO3 nanoparticles. LiNbO3 has been prepared successfully via a molten salt route at 6500c using lithium chloride and lithium carbonate as a flux and niobium oxide as niobium source. This resulted in a very high crystallinity with nanocrystals on average 90 - 120 nm in diameter. The study also analyzed the optimum degree of crystallinity in the ferroelectric polymers, PVDF and P(VDF-TrFE). In order to achieve high crystallinity in PVDF and its copolymer, the spin coated polymer substrate needs to be annealed to a certain temperature. The optimum temperature to ensure the , highest crystallinity is found to be in the range 1300c - 140"C. Vacuum annealing also increased the crystallinity to a certain degree. The properties of a composite mixture between polymer P(VDF-TrFE) and LiNb03 were studied to understand its ferroelectric characteristics. The composite, with 0-3 connectivity, was processed using 3 different types of surface active agents; silane, poly (acrylic acid co-maleic acid) and a commercial deflocculant, KD!. A microstructure study showed only sUane provided strong binding between the matrix and LiNbQ3 particles. Polarization - electric field (P-E) hysteresis loops proved to be unsaturated; however a calculation showed that only 40% of the applied voltage was applied to the LiNbO3 particles, because of difference in permittivity values of each constituent hence the coercive field was not exceeded. The composite permittivity was also graphically fitted to a theoretical formula (Lichtenecker and Yamada) to understand its microstructure pattern connectivity.
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Abernethy, Joyce Anne. "Novel devices in periodically poled lithium niobate." Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/15473/.
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This thesis describes the research carried out to develop several novel periodically poled lithium niobate (PPLN) devices. These devices exploit the ability to invert micro-domains of spontaneous polarisation in ferroelectrics such as lithium niobate. The fabrication of PPLN devices is described and extensive studies into factors influencing the poling quality are presented. In particular a comparison of material properties of unprocessed lithium niobate material from a range of different suppliers is carried out. Several novel PPLN devices are reviewed and two main devices are investigated - an electro-optically controlled Bragg grating modulator for laser beam switching and modulation and a titanium indiffused waveguide in PPLN for frequency conversion. The design, fabrication and operation of the electro-optic Bragg modulators is described and results for the first infrared operation at 1064nm of such a device are presented. Several discrepancies are seen between experimental results, both in this thesis and previously published results, and a theoretical model based on Kogelnick?s coupled wave analysis. These anomalies are further investigated at visible operation (633nm and 488nm) and solutions and methods for alleviating the discrepancies are presented. Work on titanium indiffused channel waveguides in PPLN is reported, including a study into fabrication issues and the demonstration of second harmonic generation of 416nm in such a device.
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Chen, Li. "Hybrid Silicon and Lithium Niobate Integrated Photonics." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429660021.
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Valdivia, Christopher E. "Light-induced ferroelectric domain engineering in lithium niobate & lithium tantalate." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/65500/.
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The influence of illumination on ferroelectric domain engineering in lithium niobate and lithium tantalate is investigated. The conventional method of domain inversion is electric field poling, which suffers from several limitations such as a requirement for photolithography and high-voltage equipment, the formation of inhomogeneous electric fields, and a minimum domain size of micrometres. Through the use of directed laser light, either in the presence or absence of an externally applied electric field, these limitations can be overcome and new fabrication capabilities are revealed. Light-assisted poling is the simultaneous application of an external electric field and laser illumination. Using wavelengths ranging from near-UV to near-IR, the electric field required for domain nucleation was reduced for increasing intensities. This effect was most prominent in crystals highly doped with MgO, achieving a reduction of 90% and 98% for cw and fs-pulsed light, respectively. Arbitrary domain patterns were directly written by the scanning of a focused beam. Periodically poled gratings were formed using periodic intensity patterns via a phase mask, forming domain engineered crystals suitable for quasi-phase-matched nonlinear frequency conversion.
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Wellington, Iain. "Direct UV writing of structures in lithium niobate and lithium tantalate." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/50699/.
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This thesis presents results from fabrication of UV direct write structures in lithium niobate and lithium tantalate. Unassisted direct writing of surface channel waveguides using lambda = 244 nm cw light resulted in polarisation specific waveguides fabricated on z- cut crystals. Waveguides were characterised using mode profiles, propagation losses, numerical aperture and refractive index measurements. In z-cut congruent lithium niobate, waveguides were written on the +z and -z faces producing structures that guided TM polarisation only with +z face waveguides exhibiting the lowest propagation loss of ~ 2 dB/cm, a maximum refractive index difference of ~ 8 x 10Surface ferroelectric domain reversal via illumination of single pulsed lambda = 266 nm light through a phasemask on +z face congruent lithium niobate produced ordered alignment of domain lines along the crystallographic y-axes with minimum domain separation width of ~ 2 μm. Results from high temperature exposures and multipulse regimes are presented and a domain formation mechanism is proposed via an Nb anti-site model.
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Paul, Marcus. "Synthesis and characterisation of transition metal-doped lithium niobate and lithium tantalate." Thesis, University of Aberdeen, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319341.
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The study of ferroelectric LiNbO3 and LiTaO3 doped with transition metals involves the characterisation of LiNbO3/LiTaO3 solid solutions in the systems Li2O-Nb2O5-MxOy and Li2O-Ta2O5-MxOy (M = Cr, Mn, Fe, Co, Ni, Cu). Compounds were made by solid state reaction at temperatures between 1000 and 1500°C, depending on the system studied. The emphasis of this work is on the characterisation of the defect structure of LiNbO3/LiTaO3 solid solutions using phase diagram determination, X-ray and neutron powder diffraction, EXAFS, ESR and optical spectroscopy. The valence of the incorporated cations was studied by magnetic measurements. The electrical properties of these materials have been investigated using AC impedance spectroscopy. It can be shown that the physical properties of LiNbO3 and LiTaO3 depend strongly on the defects in the structure which can be controlled by purposeful doping with other cations. Structural refinements of the X-ray and neutron powder diffraction data have shown that the defects arising from nonstoichiometry are accommodated by vacancies created on the Li site. This affects the structure when doped with third cations, giving rise to complex substitution mechanisms Spectroscopic studies have shown that the dopants (Cr3+, Mn2+/Mn3+, Co2+, Ni2+, Cu+, Cu2+) are shifted from the central octahedral position towards the adjacent empty octahedron. The electrical properties of LiNbO3 and LiTaO3, measured by AC impedance spectroscopy, depend strongly on the dopant content: the conductivity generally rises, whereas the activation energy for the electrical conductivity drops with increasing dopant concentration. The microstructure of electroceramics can also be probed by AC impedance spectroscopy and it was shown that the texture of all samples was bad due to poor sintering of the pellets. Longer sintering times did not improve the quality of the ceramics which exhibit a large pore size distribution. An important aspect for future work would be the quality improvement of LiNbO3/LiTaO3 based ceramics.
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Jaeger, Nicolas August Fleming. "Voltage induced optical waveguide modulators in lithium niobate." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/29118.
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Two types of optical modulator were studied, both of the voltage induced optical waveguide type first proposed and demonstrated by Channin in 1971. An optical waveguide was created in an electrooptic substrate by applying voltage between two electrodes deposited on the substrate. Channin used wide electrode spacings which resulted in large operating voltages being necessary. The devices discussed in this thesis had much smaller electrode spacings and therefore operated at much reduced voltages. They are of the planar and ridge types. In the planar type the electrodes were deposited on top of a planar substrate and in the ridge type a ridge of electrooptic material separated thick electrodes. The theory of operation for both types of device was developed and they were modeled, fabricated, and tested. Numerically derived results were obtained for light with wavelengths of 442 and 633 nm which showed that the confinement of the light increased with increasing voltage, decreasing gap width, and decreasing wavelength. The theory was further developed to investigate the performance of the device as a voltage-controlled linking waveguide between two optical fibers. The optimum coupling efficiency, as a function of voltage and interelectrode gap width, from optical fibers to both types of device was calculated in terms of the model. Key aspects of the theory were confirmed by the measurements made on the fabricated devices. A planar device was used as a front-end switch between a laser and an optical fiber using a V-groove etched in silicon to align the voltage induced waveguide with the fiber. One problem was a decay phenomenon in which the induced waveguide disappeared over a period of time during which a constant voltage was applied to the electrodes. This was believed to be due to the photorefractive effect. It was found that the device would recover upon the application of a fly-back cycle.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
15
Pooley, Marina J. "The preparation and characterisation of nanocrystalline lithium niobate." Thesis, University of Kent, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399594.
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Sones, Collin Lawrence. "Domain engineering techniques and devices in lithium niobate." Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/15474/.
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This thesis presents the results from investigations directed at novel approaches to domain engineering single-crystal congruent lithium niobate at the micron/sub-micron scale for practical device applications. Experimental etch-rate measurements from a parametric study of etch-rates and etch-quality of single-crystal lithium niobate z-faces, as a function of specific ratios for mixtures of HF/HNO3, to ascertain whether the widely-employed 1:2 mixture was in fact optimum for achieving the largest differential etch-rates between lithium niobate z-faces, revealed that pure HF produced an etch-rate that is a factor of two higher than that for the more frequently used 1:2 mixture. The observed etch-quality as compared to the 1:2 ratio was also improved for either pure HF or HF/HNO3 in a 1:4 ratio. A discussion of the etch-chemistry involved, and an explanation of the observed difference in etch-rates between the +z and -z faces has been proposed. The experimental results are also suggestive of a second differential etch-rate between virgin and newly poled z-faces. The observed variation in the differential etch-rate as a function of time-delay following poling, was suggestive of small atomic displacements following poling, and was quantified by the evidenced shifts in six major Raman spectral peaks. The noticeable modifications in the etch-behaviour of undoped congruent z-cut lithium niobate by pre-illumination with sub-picosecond UV-laser radiation of 248nm wavelength at energy fluences below the ablation threshold, demonstrates the potential applicability of this technique for μm-scale surface structuring of lithium niobate. An innovative technique for surface domain-inversion, based on the conventional e-field poling, but involving an intentional over-poling step, was employed to fabricate 1D and 2D periodic structures with good domain uniformity. Domain periods as short as ~1μm have been achieved, and the technique shows full compatibility with standard waveguide fabrication techniques in lithium niobate. Quasi-phase matched harmonic generation at the fundamental wavelength of 1.064 μm, by means of the first-order (G10) reciprocal lattice vector, from a surface hexagonally poled planar annealed proton exchanged waveguide, with domain period of 6.7μm, was demonstrated. First-order quasi-phase matched blue light generation with reasonable efficiencies at 413.17nm, with domain periods of 2.47μm from a surface poled Ti-indiffused channel waveguide was also demonstrated. Finally an novel route, sequentially employing techniques such as photolithographic patterning, e-field poling, direct-bonding and domain-sensitive differential wet etching for the fabrication of freestanding piezoelectric micro-cantilevers in single-crystal lithium niobate, with MEMS/MOEMS end-applications, was demonstrated.
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McCoy, Michael Anthony. "Microstructural characterization of titanium : lithium niobate optical waveguides /." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487676847118483.
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Peace, Daniel C. "Thin-film Lithium Niobate for Integrated Quantum Optics." Thesis, Griffith University, 2022. http://hdl.handle.net/10072/420851.
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The generation of broadband squeezed light is a vital resource within continuous-variable quantum information processing. In light-based quantum computation protocols, the amount of squeezing impacts computation error rates, therefore achieving fault-tolerant quantum computation requires a sufficiently high level of squeezing. Traditionally, squeezed light has been generated using bulk nonlinear crystals located within optical cavities, however this comes at the cost of a narrow squeezing bandwidth which reduces operational speed. Recently, the thin-film Lithium Niobate has emerged as a promising material platform for the generation of broadband squeezed light, however current demonstrations have been limited. In this work using periodically polled nanophotonic waveguides in thin-film Lithium Niobate, we study the generation and manipulation of broadband squeezed light. In utilising the high peak powers offered by ultrashort pulses we demonstrate for the first time, the generation of broadband squeezed light in a Silicon-Nitride strip loaded thin-film Lithium Niobate waveguide at telecommunication wavelengths. Furthermore, we theoretically investigate the performance of an integrated coherent feedback squeezer, a device which enables coherent control over the level of squeezing. These results contribute to the realisation of a fault-tolerant photonic quantum computer and development of continuous-variable quantum information processing.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
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Pozza, Gianluca. "Development of an Optofluidic Platform in Lithium Niobate." Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424115.
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Optofluidics is a promising interdisciplinary research and technological field, thanks to its wide potential of application in sector like medicine, chemistry, biology and environmental science. In this context the study of innovative materials including their properties, their efficiency, their limits and their possibility of leading to miniaturized devices is the key point for the overcoming of currently adopted strategies. A promising material that could satisfy new optofluidic requirements is Lithium Niobate (LiNbO3 - LN) thanks to its excellent optical and nonlinear optical properties.
In this work we demonstrated for the first time the applicability of the Lithium Niobate as a high intagrable and tailorable substrate for optofluidics. As a matter of fact, we developed all the several stages that can be interconnected to realize a platform with complex optofluidic functionalities: from the droplets generation and manipulation, to their transfer through a microfluidic channel directly engraved on the crystal substrate, to the droplets optical analysis stage.
In particular in this thesis we present the first high performant T-Junction droplet generator completely engraved in LN, and the first Ti in-diffused channel waveguide coupled with a microfluidic channel in the same substrate. Furthermore a study on the wetting properties of the Lithium Niobate is discussed.
Concerning the optical stage we discuss the realization of optical frequency converter realized in LN, which plays a key role in the development of our optofluidic platform. In fact it can be used to integrate a laser source in the green-blue range that could found application particularly in the biological field. Moreover we present the first frequency converter in the PPLN configuration realized in Zirconium doped LN, a dopants that prevent the optical damage and therefore could increase the intensity of work and the efficiency of conversion of the devices. Also we implemented the process to produce single-mode channel waveguide by Ti in-diffusion as interconnection stage for the optical circuit.
Concluding, we were able to implement a well-equipped tool-box for the incorporation of different devices on the same substrate, demonstrating for the first time the integration of all the different stages in a single substrate, and paving the way to an extreme optofluidic integration in Lithium Niobate.L’optofluidica è un promettente settore di ricerca interdisciplinare con altrettante interessanti applicazioni tecnologiche. Questo grazie al suo ampio potenziale in settori quali la medicina, la chimica, la biologia e le scienze ambientali. In questo contesto uno studio di materiali innovativi che includa le loro proprietà, la loro efficienza, i loro limiti e la loro possibilità di produrre dispositivi miniaturizzati è fondamentale per superare le attuali strategie adottate. Un materiale promettente per soddisfare i requisiti dell’optofluidica è il Niobato di Litio (LN o LiNbO3), un materiale conosciuto per le sue eccellenti proprietà ottiche lineari e non lineari e che qui discutiamo per la prima volta in un contesto optofluidico. In questo lavoro abbiamo dimostrato l’applicabilità del Niobato di Litio come substrato altamente integrabile e adattabile per l’optofluidica. Abbiamo infatti sviluppato tutti i diversi stadi che possono essere interconnessi per realizzare una piattaforma con funzionalità complesse optofluidiche: dalla produzione di gocce, alla loro manipolazione, al loro trasporto in canali microfluidici realizzati nel cristallo, fino all’analisi ottica delle stesse. In particolare nella tesi sono presentati il primo generatore di gocce a giunzione a T completamente fabbricato su Niobato di Litio e la prima guida d’onda a canale in Titanio diffuso accoppiata con un canale. Infine abbiamo proposto il primo studio completo sulla bagnabilità del Niobato di Litio. Per quanto riguarda lo stadio ottico, abbiamo realizzato dei convertitori di frequenza ottica, dispositivi che giocano un importante ruolo nel progetto, in quanto possono essere usati come sorgenti laser integrate con emissione nell’intervallo verde-blu, uno spettro che trova molte applicazioni nell’ambito biologico. In questo contesto abbiamo realizzato il primo convertitore di frequenza con configurazione PPLN realizzato su Niobato di Litio drogato Zirconio, un nuovo tipo di drogante che prevenendo il danno ottico è in grado di aumentare l’intensità di lavoro e l’efficienza di conversione di questi dispositivi. Abbiamo infine implementato il processo per produrre guide ottiche a canale monomodo per diffusione di Titanio, dispositivi necessari per connettere le diverse parti del circuito ottico. In conclusione con questo lavoro abbiamo implementato un’ampia categoria di dispositivi, per la prima volta tutti contemporaneamente integrabili su un singolo substrato. Abbiamo perciò aperto la strada verso un’elevata integrazione di funzionalità optofluidiche su Niobato di Litio.
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Harhira, Aïssa. "Photoluminescence polaron dans le niobate de lithium : approche axpérimentale et modélisation." Thesis, Metz, 2007. http://www.theses.fr/2007METZ052S/document.
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Le niobate de lithium (LN), en raison de ses propriétés, électro-optiques, optiques non linéaires et photoréfractives (PR) , s'impose comme un matériau de choix pour des applications en modulation, filtrage, stockage holographique ou conversion de fréquence optique. L'effet PR est gouverné à la fois par les centres profonds extrinsèques (Fe2+ et Fe3+ le plus souvent) et par les antisites niobium en site (Nbli5+), qui constituent des pièges préférentiels pour les électrons arrachés aux donneurs profonds et forment ainsi des polarons liés Nbli4+, caractérisables par une large bande d'absorption photo-induite (API) s"étendant dans le rouge et le proche infrarouge, ainsi que par une bande de photoluminescence (PL) légèrement décalée en longueur d'onde par rapport à la précédente. Nous présentons ici une étude expérimentale de la PL polaron dans le LN congruent dopé fer, fonction de la température et de l'intensité lumineuse excitatrice, en régime continu et en régime pulsé, ainsi qu'un modèle phénoménologique à trois centres permettent d'interpréter toutes les caractéristiques observées. Nous montrons que la PL permet en principe de doser les donneurs profonds dans le LN congruent en qualité infime, que soit leur nature. Pour les ions Fe2+, la détectivité est typiquement de 0,25 ppm à l'ambiante, ce qui est bien meilleur que la spectroscopie d'absorption. La PL résolue spatialement permet en outre, contrairement aux autres techniques, de cartographier la concentration de donneurs profonds à l'échelle micrométrique, d'où son potentiel pour la caractérisation de guides d'onde, de composants optiques intégrés ou autres microstructuresBecause of their electro-optical, non-linear optical and photorefractive effet, lithium niobate crystals (LN) are used in many applications such as modulation, filtering, holographic storage or frequency conversion. Its known that the photorefractive effect is influenced by both extrincic deep centers (Fe2+ and Fe3+ in most cases) and by niobium antisites (Nbli5+) which constitute preferential sites to trap an electron hence giving a small bound polaron (Nbli4+). This defect is characterized by a photo_indiced obsorption (API) broad band in the NIR range, as well as slightly Stokes shifted photoluminescence band (PL). We presnt nerein an experime,tal study of the polaron related PL in iron doped congruent lithium niobate as a function of temperature and incident intensity in CW and pulsed regime. We also propose a phenomenological threecenter model as an interpretation of all observed results. We show that the PL permits one to determine the concentration of deep centres in congruent LN in trace amounts, whatever their nature. For Fe 2+ ions, the sensitivity is typically around 0,25 ppm at RT, which is better than absorption spectroscopy. In addition, unlike other techniques, the PL is spatially resolved (micrometer scale) which allows to maps the concentration of deep donors, hence its potential for characterizating waveguides, integrated optical components and other microstructures
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Reza, Selim. "Acoustooptically tunable waveguide lasers in erbium doped lithium niobate." [S.l.] : [s.n.], 2006. http://ubdata.uni-paderborn.de/ediss/06/2006/reza.
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Kuo, Hsin-Hui. "Investigation of an electrooptic tunable filter in lithium niobate." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5858.
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A polarization independent electrooptic add/drop tunable filter fabricated on a
LiNbO3 substrate with a narrow -3 dB bandwidth (FWHM) of 1.56 nm operating in the
1.55 üm wavelength regime has been developed to meet the demands of fast tuning
speed and increased channel capacity for dense wavelength division multiplexed
(WDM) networks. The operation of the filter is based on passive polarization beam
splitters and strain-induced phase-matched TEâÂÂTM polarization mode converters.
Extinction ratios as high as 20 dB for polarization beam splitters were achieved using
zero-gap two-mode interference directional couplers with an opening angle of 0.55ð. A
tunable TEâÂÂTM polarization mode converter with 98.2 % conversion efficiency was
obtained using a strain-induced refractive index grating consisting of 765 parallel strips
10.5 üm wide in a strained SiO2 surface film with a spatial period of 21 üm. Thermal and
electrooptic tuning of the polarization mode converters were examined. A polarization
independent electrooptic add/drop tunable filter in which the fabrication parameters of
the splitter and the mode converter were optimized was produced. Fiber-to-fiber
insertion loss less than 6.3 dB was measured on a 62 mm long filter device. The spectral characteristics reveal a -3 dB bandwidth of 1.56 nm and nearest sidelobes about 12 dB
below the center peak. A thermal tuning rate of -0.903 nm/ðC was realized. Electrooptic
tuning was also demonstrated. A tuning range of 14.08 nm with applied DC voltages
from -80 V to +80 V was achieved indicating an electrooptic tuning rate of 0.086 nm/V.
The filter performance for both TE and TM modes was examined and polarization
independence of the spectral characteristics was confirmed.
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Benmouhoub, Chafia. "Lab-on-chip opto-électronique sur Niobate de Lithium." Thesis, Besançon, 2014. http://www.theses.fr/2014BESA2068.
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Les travaux de cette thèse s’inscrivent dans un projet de développement d’un Lab-On-Chip destiné à la biodétection. Les plateformes conçues sont basées sur des circuits optiques intégrés sur niobate de lithium. La particularité de ces circuits est qu’ils intègrent le phénomène d’interférence à la fonction de guidage des ondes lumineuses.La fonction d’interférométrie est assurée grâce à une cavité Fabry-Pérot intégrée à un guide d’onde rectiligne et à une structure Mach-Zehnder. Lorsque la surface des supports de ces circuits est bio-fonctionnalisée, ces microsystèmes deviennent sensibles à des molécules cibles. Cette sensibilité se traduit par une variation de l’indice effectifde l’onde en propagation par couplage évanescent modifiant ainsi les conditions de résonance du résonateur Fabry-Pérot. Le vrai challenge de ce travail réside essentiellement dans la bio-fonctionnalisation du niobate de lithium.A notre connaissance, ce matériau favori en optique guidée grâce à ses propriétés physiques exceptionnelles n’a été que rarement sujet à des modifications chimiques de surface. L’implantation réussie de groupements fonctionnels amines à la surface de ce matériau a permis de générer un lien covalent entre ce support et les groupements fonctionnels des molécules sondes. En raison de la grande affinité entre l’avidine et la biotine, ce couple a servi de modèle pour la mise au point de ces bio-capteurs. Un suivi en temps réel des interactions à la surface était rendu possible par une expérimentation sur l’un des bio-capteursThe work of this thesis is part of a project of a Lab-On-Chip development intended for biosensing. The de-signed platforms are based on integrated optical circuits on lithium niobate. The peculiarity of these circuits isthat they incorporate the phenomenon of interference with the function of guiding light waves. The interferometricfunction is provided by a Fabry-Perot cavity embedded in a straight waveguide and a Mach-Zehnder structure.When the surface of these circuits substrates is biofunctionalized, these microsystems become sensitive to targetmolecules. This sensitivity results in a variation of the effective index of the propagation wave by evanescent cou-pling and modifying the resonance conditions of the Fabry-Perot resonator. The real challenge of this work liesin the biofunctionalization of lithium niobate. To our knowledge, this guided optics favorite material thanks toits exceptional physical properties has been hitherto rarely subject to chemical surface modifications. Successfulimplementation of amino functions on the surface of this material has generating a covalent bond between thissubstrate and the functional groups of the probe molecules. Due to the high affinity between avidin and biotin, thiscouple served as a model for the development of biosensors. A real-time monitoring of surface interactions wasmade possible by experimentation on one of biosensors
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Swanson, Claudia H., Michael Schulz, Holger Fritze, Jianmin Shi, Klaus-Dieter Becker, Peter Fielitz, and Günter Borchardt. "Examinations of high-temperature properties of stoichiometric lithium niobate." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186802.
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Scott, Jeffrey Gordon. "Laser-assisted surface and domain microstructuring of lithium niobate." Thesis, University of Southampton, 2005. https://eprints.soton.ac.uk/30235/.
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This thesis presents the results of investigations into the nano-structuring of lithium niobate using the combined or sequential action of laser light and a chemical etch (a mixture of hydrofluoric and nitric acids). Novel methods to characterise ferroelectric domains using Raman spectroscopy and surface second harmonic generation are also described. The use of Raman spectroscopy as a diagnostic technique for recently poled lithium niobate was investigated. The position of several Raman peaks were observed to be shifted following electric-field domain inversion; some these peaks returned to their original positions with a characteristic time constant that is related to the recovery of the internal field of lithium niobate. Surface second harmonic generation was also shown to be able to distinguish between opposite z faces of virgin and poled lithium niobate.
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Jones, Julian Kelly. "Diffusively doped thulium- and ytterbium-lithium niobate waveguide lasers." Thesis, University of Southampton, 1995. https://eprints.soton.ac.uk/399106/.
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This thesis describes the work carried out on diffusively doped Tm - and Yb - Ti:LiNbO3 waveguide lasers. During the course of this investigation the fabrication, spectroscopy, and laser characterisation of the resulting devices was performed. Rare earth doping was accomplished using the thermal indiffusion technique, which is a highly flexible method for doping this very useful optical material. This study produced the first Yb:LiNbO3 laser, and the first room temperature Tm:LiNbO3 laser. Also the first detailed spectroscopy of Yb:LiNbO3 was performed here. Laser emission was seen in a Yb:LiNbO3 Ti waveguide at 1008, 1030 and 1060nm, with a threshold of 15mW absorbed pump power. The threshold in a Tm:LiNbO3 Ti waveguide was 17mW and lasing was seen at 1.81 and 1.853 µm. The laser potential of the 1G4 to 3H6 transition at about 470nm in Tm:LiNbO3 was also examined, using absorption spectroscopy and McCumber analysis. Photorefractivity, however, adversely affected the laser performance of these devices, and a number of methods for eliminating photorefractivity were applied for the first time to waveguide lasers. In an attempt to reduce photorefractivity a Tm:LiNbO3 Ti waveguide was successfully periodically poled using the wet electrode technique; this did not, though, eliminate photorefractive damage in the resulting device. A Tm:LiNbO3 Ti waveguide laser doped with the rare earth at above the Curie point of LiNbO3 was, however, non photorefractive, and an oxygen anneal process was also successfully used in a Yb:LiNbO3 laser. Although the majority of the work presented here was on LiNbO3, some work, however, was also carried out on the widely used laser crystal YAG (Y3Al5O12). Here a new method of waveguide fabrication in YAG was investigated, this is described at the end of this thesis.
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Swanson, Claudia H., Michael Schulz, Holger Fritze, Jianmin Shi, Klaus-Dieter Becker, Peter Fielitz, and Günter Borchardt. "Examinations of high-temperature properties of stoichiometric lithium niobate." Diffusion fundamentals 12 (2010) 48, 2010. https://ul.qucosa.de/id/qucosa%3A13886.
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Nutt, Alan C. G. "Techniques for fabricating integrated optical components on lithium niobate." Thesis, University of Glasgow, 1985. http://theses.gla.ac.uk/7969/.
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Chen, Bo Xu Chang-Qing. "All-optical quasi-phase-matched lithium niobate wavelength converters." *McMaster only, 2006.
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Mhaouech, Imed. "Étude du transport de charges dans le niobate de lithium massif et réalisation de fonctions électro-optiques dans le niobate de lithium périodiquement polarisé." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0032/document.
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Le premier volet de cette thèse est consacré à la modélisation des phénomènes de transport dans le LN. Partant d'une analyse critique des modèles de bande usuels, nous montrons leur inadéquation dans le cas du LN et nous proposons un modèle de saut basé sur la théorie des petits polarons. Nous étudions d'abord par simulation Monte-Carlo la décroissance d'une population de polarons liés NbLi4+ relaxant vers des pièges profonds FeLi3+. Nous montrons que les pièges FeLi3+ ont des rayons effectifs particulièrement grands, rayons qui augmentent encore à température décroissante, et limitent considérablement les longueurs de diffusion des polarons. Les résultats de simulations sont ensuite confrontés aux résultats expérimentaux obtenus par différentes techniques ; Absorption photo-induite, Raman, Enregistrement holographique et Pompe-sonde. Le deuxième volet de cette thèse est consacré aux applications électro-optiques dans le LN périodiquement polarisé (PPLN). Sous l’effet d’une tension électrique, l’indice de réfraction du PPLN est périodiquement diminué et augmenté, formant ainsi un réseau d’indice activable électriquement. Un premier composant utilisant l’effet électro-optique dans du PPLN a été développé et démontré expérimentalement. Dans ce composant, la lumière est défléchie sous l’effet de la tension électrique par le réseau d’indice. Ce déflecteur de Bragg atteint une efficacité de diffraction proche de 100% avec une faible tension de commande de l’ordre de 5 V. Un deuxième composant a également été proposé, où la lumière se propage perpendiculairement aux parois de domaines du PPLN. Dans cette configuration un réflecteur de Bragg électro-optique peut être réaliséThe first part of this thesis is devoted to the modeling of transport phenomena in the LN. From a critical analysis of the usual band models, we show their inadequacy in the case of LN and we propose a hopping model based on the theory of small polarons. We first study by Monte-Carlo simulation the population decay of bound polarons NbLi4+ in deep traps FeLi3+. We show that the traps (FeLi3+) have particularly large effective radii, which increase further at decreasing temperature, and considerably limit the diffusion lengths of the polarons. The results of simulations are then compared with experimental results obtained by different techniques; Light-induced absorption, Raman, Holographic storage and Pump-Probe. The second part of this thesis is devoted to electro-optical applications in the periodically poled LN (PPLN). Under the effect of an electrical voltage, the refractive index of the PPLN is periodically decreased and increased, thus forming an electrically activatable index grating. A first component using the electro-optical effect in PPLN has been developed and demonstrated experimentally. In this component, the light is deflected under the effect of the electrical voltage by the index grating. This Bragg deflector achieves a diffraction efficiency of close to 100% with a low drive voltage of the order of 5 V. A second component has also been proposed, where light propagates perpendicularly to the domain walls of the PPLN. In this configuration an electro-optic Bragg reflector can be realized
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Majkić, Aleksej. "Electro-optically tunable microring resonators in fluorine-implanted lithium niobate /." Zürich : ETH, 2009. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18179.
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Grisard, Arnaud. "Lasers guides d'onde dans le niobate de lithium dopé erbium." Phd thesis, Université de Nice Sophia-Antipolis, 1997. http://tel.archives-ouvertes.fr/tel-00089120.
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Le niobate de lithium dopé à l'erbium permet de tirer parti des propriétés optiques des ions terre rare et du fort coefficient électro-optique de la matrice. Il constitue ainsi un matériau prometteur pour la réalisation de lasers déclenchés monolithiques émettant vers 1,5 µm. En configuration guidée, l'obtention d'impulsions à forte puissance crête est en particulier envisageable à partir d'un pompage par diode laser du commerce et avec de faibles tensions de commande.Dans cette perspective, un mécanisme prépondérant de réduction du gain aux fortes concentrations de dopant, caractéristique des cristaux dopés dans la masse, a été identifié et une méthode originale développée pour évaluer simplement ses effets de façon quantitative.
Ce mémoire souligne l'excellent accord entre les prévisions théoriques du modèle d'amplification optique mis en place puis adapté au cas de guides monomodes et les mesures réalisés sur les composants fabriqués dans le même temps par diffusion de bandes de titane dans des substrats dopés dans la masse et en surface.
Ceci a permis d'observer pour la première fois l'effet laser en continu dans des guides d'onde sur niobate de lithium dopé à l'erbium dans la masse et pompés par une diode à 1,48 µm. L'intégration de modulateurs électro-optiques a également conduit à l'observation d'impulsions déclenchées. Pour l'instant limitées par la puissance de pompe disponible, elles devraient pouvoir atteindre plusieurs centaines de watts de puissance crête avec des durées de quelques nanosecondes.
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Nguyen, Giang Thach, and thach nguyen@rmit edu au. "Efficient Resonantly Enhanced Mach-Zehnder Optical Modulator on Lithium Niobate." RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070118.162330.
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Photonic links have been proposed to transport radio frequency (RF) signals over optical fiber. External optical modulation is commonly used in high performance RF-photonic links. The practical use of optical fiber to transport RF signals is still limited due to high RF signal loss. In order to reduce the RF signal loss, highly efficient modulators are needed. For many applications, modulators with broad bandwidths are required. However, there are applications that require only a narrow bandwidth. For these narrow-band applications, the modulation efficiency can be improved through the resonant enhancement technique at the expense of reduced bandwidth. The aim of this thesis is to investigate highly efficient Mach-Zehnder optical modulators (MZMs) on Lithium Niobate (LiNbO3) with resonant enhancement techniques for narrow-band RF-photonic applications. This work focuses in particular on analyzing the factors that affect the modulation efficiency through resonant enhancement so that the modulator electrode structure can be optimized for maximum modulation efficiency. A parameter study of the effects of the electrode characteristics on the modulation efficiency of resonantly enhanced modulators (RE-MZM) is provided. From this study, optimum design objectives are identified. Numerical optimization is employed to explore the design trade-offs so that optimal configurations can be found. A sensitivity analysis is carried out to assess the performance of optimal RE-MZMs with respect to the variations of fabrication conditions. The results of these investigations indicate that the RE-MZM with a large electrode gap is the optimal design since it provides high modulation efficiency although the inherent switching voltage is high, and is the most tolerant to the fabrication fluctuations. A highly efficient RE-MZM on X-cut LiNbO3 is practically demonstrated with the resonant enhancement factor of 5 dB when comparing to the unenhanced modulator with the same electrode structure and effective switching voltage of 2 V at 1.8 GHz. The performance of the RF-photonic link using the fabr icated RE-MZM is evaluated. Optimization of RE-MZMs for operating at millimeter-wave frequencies is also reported. Factors that limit the modulation efficiency of an RE-MZM at millimeter-wave frequencies are identified. Novel resonant structures that can overcome these limitations are proposed. Preliminary designs indicate that greatly improved modulation efficiency could be expected.
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Schmarje, Nicole. "Lithium niobate piezocomposites for high temperature applications in nondestructive testing." Thesis, University of the West of Scotland, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427710.
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Manzo, Michele. "Influence of selective proton exchange on periodically poled lithium niobate." Thesis, KTH, Kvantelektronik och -optik, QEO, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-164586.
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The purpose of the present thesis is to study the influence of Proton Exchange on Electric Field assisted Poling of congruent Lithium Niobate and its applications on periodically pat-terned structures. Moreover, the possibility of using Proton Exchange to avoid neighbours domains merging is studied and successfully demonstrated for period shorter than 10μm. Before approaching the poling of periodically patterned LiNbO3 samples, the main charac-teristics of the evolution of the poling of uniform samples in different masking conditions are investigated. It is well known that the kinetics of domains switching is highly dependent on the poling setup and on the quality/type of electrode employed to contact the crystal to the high voltage. We used a thin layer of Titanium both as mask for proton diffusion and as metal electrode for poling experiments. Moreover different masking configurations are pre-sented and characterized. The second part of this work deals with the periodic poling of 0.5mm-thick congruent lith-ium niobate. 9x4 mm2 1-D Ti gratings with 8.66μm and 8.03μm period were first fabricated on the +z side of the crystal and a superficial chemical pattern was reproduced via acid bath. Three different types of samples were obtained and before the poling the metallic mask was removed whereas in one configuration it was left assuring better homogeneity of the in-verted areas. The results we obtained suggest it could be possible to achieve periodically poled congruent lithium niobate gratings with period shorter than 4μm in ~500μm thick samples and hence obtain aspect ratios of more than 250.
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Loni, Armando. "An experimental study of proton-exchanged lithium niobate optical waveguides." Thesis, University of Glasgow, 1987. http://theses.gla.ac.uk/1586/.
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The object of this thesis is to form an understanding of the origin of the problems associated with proton-exchanged waveguides, and to investigate possible solutions. Chapter 1 gives a brief introduction to the properties of lithium niobate, and discusses the methods available for fabricating optical waveguides in the bulk material, with particular emphasis on waveguide fabrication by the proton-exchange process. Some of the devices which have been fabricated by proton-exchange are discussed. The problems associated with proton-exchanged waveguides are reviewed. Chapter 2 deals with the physical and chemical characterisation of proton-exchanged waveguides fabricated using neat benzoic acid melts. The extent of proton-exchange is determined as a function of fabrication time and temperature using optical waveguide prism-coupler measurements, infrared absorption spectroscopy, and atomic absorption spectroscopy. Chapter 3 is concerned with the problem of waveguide mode-index stability. Using a hydrogen isotopic-exchange reaction, the extent of which is obsrved via infrared absorption spectroscopy, information on the (room-temperature) mobility of protons within the guiding layer is obtained for waveguides fabricated using neat benzoic acid melts. The recently reported process of fabricating waveguides in lithium niobate by deuterium-exchange is investigated. The behaviour of proton-exchanged and deuterium-exchanged waveguides with respect to reaction with atmospheric water vapour is investigated, and the optical properties of deuterium-exchanged waveguides are studied. In Chapter 4, a study of annealed and dilute-melt proton-exchanged waveguides is presented. It is shown, using prism-coupler measurements and infrared absorption spectroscopy, that ennealed and dilute-melt waveguides can have very similar optical properties, depending on the amount of annealing and the lithium benzoate mole-fractions used. The extent of proton-exchange is determined with time (between 215oC and 235oC) for dilute-melt waveguides produced using lithium benzoate mole-fractions of up to 1.1%. Isotopic-exchange in annealed and dilute-melt waveguides is also investigated, both at room-temperature and at temperatures commonly used for annealing. A possible explanation for the poor optical properties of (neat-melt) proton-exchanged waveguides is given. Chapter 5 deals with a study of propagation losses (using the two-prism method) and the electro-optic effect in x- and z-cut proton-exchanged waveguides. Measurements of r33 (in proton-exchanged waveguides) and r22 (in titanium-indiffused waveguides) are carried out using an external interferometric method designed by the author. The results of Chapter 4 are used to establish a method by which losses below 0.5dB/cm and a substantially restored electro-optic effect can be achieved (using a combination of dilute-melt fabrication with post-exchange annealing). Prior to the waveguide measurements, the bulk electro-optic effect is investigated for congruent, incongruent, MgO-doped, and annealed (high-temperature) crystals. Finally, in Chapter 6, a summary of the thesis is presented, and suggestions for future work are given.
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Mills, P. A. "Volume holographic infra-red filters in iron doped lithium niobate." Thesis, University of Oxford, 1985. http://ora.ox.ac.uk/objects/uuid:01d6f3ab-692e-40a5-9f60-d67ebee96bd7.
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Two collimated laser beams, wavelength O-514 μm are overlapped within a crystal of heavily iron doped lithium niobate to form a one-dimensional volume holographic grating, a few mm long, designed to behave as a highly selective filter at near infra-red wavelengths. A novel recording geometry is described and a variety of diagnostic experiments are undertaken to determine the main characteristics of the grating. A filter fabricated using this method is used to obtain single mode operation from a 1-55 μm semiconductor laser. The historical survey of holography contained in chapter one emphasizes the dynamic properties and applications of photorefractive recording materials. Standard results of two mathematical theories, kinematic and coupled-wave, are used in chapter two to predict the properties of a Bragg grating when replayed with infra-red light. Chapter three details the recording materials suitable for an infra-red filter, followed by a discussion on the concept of 'scaling'. The recording mechanism of iron doped lithium niobate, including its fixing and erasure process, is presented in chapter four as a basis for selecting the most advantageous crystal characteristics. Mathematical models describing the complex dynamic recording process in iron doped lithium niobate are introduced in chapter five. A novel recording geometry involving the use of two prisms is critically described in chapter six, from initial conception to final implementation. The performance of the grating as an infra-red filter is assessed in chapter seven by measuring the angular response of the transmitted and diffracted beams at a wavelength of 1-152 microns. Chapter eight discusses the applications for volume holographic filters, with particular reference to one example. In chapter nine general conclusions are drawn and future directions for research are suggested. A number of appendices are also included.
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Zisis, Grigorios. "Laser-induced ferroelectric and photonic structures in lithium niobate crystals." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/415431/.
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The influence of laser illumination on ferroelectric domain engineering, waveguide formation and surface micro-structuring in lithium niobate (LN) is investigated. The ability to combine and to manipulate the size and depth of poling inhibited (PI) domains, which are produced by UV-laser irradiation of the +z face of congruent lithium niobate crystals followed by electric field poling, is demonstrated. It is therefore possible to produce complex domain structures, by partially overlapping individual UV laser irradiated tracks thus increasing the utility of this method for the fabrication of surface microstructures. Investigation of the electro-optic performance of ferroelectric/photonic composite structures, which occur naturally as a consequence of the PI process, had shown a significant enhancement (by ~ 36.7 % under the experimental conditions used) of the inherent electro-optic coefficient of the crystal attributed to large range stress at the domain boundaries. The feasibility of UV laser induced PI domain engineering in proton exchanged waveguides in LN was investigated showing that PI domain inversion is in principle possible. It requires however high laser intensity illumination which may produce significant surface damage. Additionally it was found that the proton concentration was also affected by the UV laser irradiation resulting in modifications of the original proton exchanged waveguide structure. Finally, an alternative to UV laser irradiation as a means for PI domain engineering and waveguide formation in LN is presented. This alternative method uses visible c.w. laser irradiation and an amorphous silicon absorbing layer to couple energy into the LN crystal thus emulating the direct absorption that occurs at UV wavelengths.
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Britton, Paul Elwyn. "Fibre laser pumped periodically poled lithium niobate based nonlinear devices." Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/15496/.
Full textAbstract:
Four experiments have been demonstrated, each successfully combining PPLN crystals and fibre lasers. Firstly second harmonic generation (SHG) was achieved with an 83% conversion efficiency using an all-fibre based nanosecond pump. 60% efficiency was achieved with a simple Q-switched Erbium fibre laser. Cascading two PPLN samples created a 33% and 15% conversion of the pump to the third harmonic, for each source respectively. A second experiment used a picosecond all-fibre chirped pulse amplification source for parametric generation, and amplification of a CW diode seed. Very high gain, in excess of 90dB, was achieved, demonstrating PPLN's high nonlinearity with the powers now available from fibre lasers. A simple Q-switched Erbium fibre laser pumped by a diode was developed for the third experiment. Energies up to 180µJ were produced, which at the time was a record for this type of source. The output was frequency doubled by a PPLN sample, before pumping a second crystal for singly resonant parametric oscillation. A low threshold of 10µJ was achieved with a broad spectral tunability of 0.945 to 4.45µm, limited only by the mirror reflectivities. The final experiment was a similar parametric oscillator but with no doubling stage. This final system is simpler to tune, with a range from 2.58 to 3.99µm. The idler to signal energy ratio was now greater. Throughout the thesis, nonlinear optical interaction theories have been studied and models developed to explain the experimental observations. All the experiments have been simulated, and major factors to the results considered. A model for the parametric processes was built based on the solution to the three time independent coupled wave equations. Numerical computations were performed, such that phase-mismatching, simultaneously competing nonlinear processes and pump depletion could be considered. The effects of focusing and spatial profiles have also been discussed.
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Archana, K. "Integrated optic devices on thin film lithium niobate for few-mode optical communications." Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5445.
Full textAbstract:
Mode division multiplexing is a remarkable strategy to meet the explosively increasing
bandwidth requirements in optical communication systems and interconnects. This scheme
harnesses the orthogonality of modes to scale the transmission capacity in communication
systems. MDM technique necessitates the development of devices that support multimodes
starting from waveguides to modulators and amplifiers, along with mode manipulating devices
like mode multiplexers and mode converters. The primary objective of this thesis is to design
and analyse multimode devices on the emerging lithium niobate on insulator (LNOI) platform.
Firstly, horizontal and vertical multimode waveguides are designed in commonly used
configurations of rib, buried and strip on both LNOI and SOI platform to compare the
performance parameters like intermodal group delay, power confinement, and waveguide
cross-sections. Characteristic equations for transverse electric (TE) and transverse magnetic
(TM) modes are derived for different cuts and optic axis orientations of LN, starting from
Maxwell’s equations. Improved coupled mode theory is applied to derive coupling coefficients
between modes of a dual-mode directional coupler. TE-TM mode coupling resulting from offdiagonal
elements in the permittivity tensor of LN is also evaluated. Then, mode hybridization
phenomenon in both X -cut Y -propagating (birefringent) and Z -propagating (isotropic) LNOI
multimode waveguides is theoretically investigated. Hybridization regions are utilized to
design tapers that convert TM0 to TE1, and TM1 to TE2. A multimode rib waveguide exhibiting
significantly large group velocity dispersions of ∼15000, 22000 and 49000 ps/nm.km at three
different wavelengths, in the regions of mode hybridizations is proposed. Mode division
multiplexers that exhibit ultra high bandwidth of 215 nm and a large fabrication tolerance of
±50 nm is designed on a rib asymmetric directional coupler. Zero birefringence (ZBR) dualmode
waveguides are proposed on X-cut Y-propagating LN with birefringence zero to four
decimal places, utilizing the interplay of intrinsic birefringence of LN and waveguide
birefringence. Minimally birefringent dual-mode waveguides are designed using off-axis
waveguide configuration. Finally, polarization-independent two-mode multiplexers/
demultiplexers are designed and analyzed
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Her, Jyh-Yan, and 何志元. "Optical Waveguides on Lithium Niobate." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/33304367893351979992.
Full textAbstract:
碩士國立成功大學
電機工程研究所
82
In recent years, due to the improvements of the techno- logies of optical fiber and semiconductor laser technology, the integrated optics has been widely used in many applica- tion fields. Lithium Niobate with its novel electro-optic effect was employed as the optical modulation material in integrated optics. In order to transfer optical wave, the waveguide is fabricate in the Lithium Niobate by two differ- ent method: proton exchange and titanium indiffusion in this thesis. The optical characteristic of the waveguide are mea- sured. The influence of process parameters on the optical characteristic are discussed. And hope that the results could found the base of integrated optics production for the late researcher.
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Chen, Chieh-Ting, and 陳玠廷. "Waveguide Faricaiton on Lithium Niobate and Third-harmonic Generation in Periodically Poled Lithium Niobate Waveguides." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/26061756428781090844.
Full textAbstract:
碩士國立臺灣大學
光電工程學研究所
90
In this thesis, we report the fabrication of channel waveguides on LiNbO3 and PPLN. The second harmonic generation and third harmonic generation in such waveguides are also discussed. Here, two methods were used for waveguide fabrication. One was the annealed proton exchange (APE) method with benzoic acid melt and the other was the proton exchange vapor (PEV) method with benzoic acid vapor. The characteristics of the waveguides showed the dependencies on guiding width, proton exchange time, annealing time and wavelength. With these two methods, single-mode and multi-mode waveguides were fabricated on LiNbO3 and periodically poled LiNbO3 (PPLN) under different fabrication conditions. Second-harmonic and sum-frequency generations with a 1560 nm femtosecond source were implemented in the fabricated waveguides. The same nonlinear processes were also implemented on bulk PPLN for comparison. Since the effective extraordinary refractive index was different in a waveguide, the phase-matching condition based on the Sellmeier equation was no longer accurate. Also, because the propagation constants varied among single-mode and multi-mode waveguides, their phase-matching conditions were different. Therefore, the results of nonlinear wavelength conversion were slightly different between bulk PPLN and waveguides of different geometries.
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Merola, Francesco. "Lithium Niobate: optical properties and applications." Tesi di dottorato, 2009. http://www.fedoa.unina.it/3785/1/Merola.pdf.
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Rost, Timothy Alan. "A thin film lithium niobate ferroelectric transistor." Thesis, 1991. http://hdl.handle.net/1911/16480.
Full textAbstract:
The incorporation of a thin film of LiNbO$\sb3$ in a conventional MOS (metal-oxide-semiconductor) structure gives the possibility of two fundamentally different types of computer memory architectures. One, based on ferroelectric switching, involves the reorganization of charge in the transistor channel to compensate for the change in surface polarization. Another, based on the bulk photovoltaic effect, creates a change in the threshold of the transistor when exposed to incident light. With the use of a molybdenum liftoff process, such ferroelectric transistors have been realized. The properties of these transistors have been measured before and after exposure to laser illumination, and before and after the application of voltage pulses.
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Lee, Bing-heng, and 李秉衡. "Fabrication of Local Periodically Poled Lithium Niobate." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/q39284.
Full textAbstract:
碩士國立臺北科技大學
光電工程系研究所
98
The processing methods for local periodically poled x-cut and z-cut lithium niobate are studied in this thesis. Local periodically poled structures are produced on lithium niobate by applying a voltage on the periodical electrodes located on the ridge. The effects of process parameters on the domain inversion results are also discussed. For the local periodically poling on x-cut lithium niobate, inductive coupled plasma etching technology is utilized to form the ridge structure. The characteristics of inductive coupled plasma etching technology are described and the effects of process parameters on the etching rate and the etching quality are discussed. As the 500V voltage is applied on the electrodes, local periodically poled structure with the duty-cycle near 50% is successfully fabricated in the ridge region. In order to periodically pole z-cut lithium niobate in the local region, the ridge is formed by using the proton exchange etching technology. As the voltage is applied on the periodical electrodes on the ridge, polarization inversion is mainly induced on the two sides of the ridge. The cause for the partial polarization inversion is that the electric field on the electrode edges is larger than that near the center of the electrode. In order to enhance the uniformity of polarization inversion region, a uniform electric field in the ridge region is required such that the periodical domain inversion with the 50% duty cycle can be effectively fabricated. Local periodically poled lithium niobate has the advantage of effective reduction of the domain inversion voltage.
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Fan, Chih-Bin, and 范智彬. "Fabrication of Microdisk Resonator on Lithium Niobate." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/thpv92.
Full textAbstract:
碩士國立臺北科技大學
光電工程系研究所
99
This thesis on the research of micro-disk resonator on lithium niobate with under-cut structure. With its horizontal and vertical high refractive index contrast, making it a more effective limitation of the light field in order to reduce light transmission caused by the loss.Under-cut structure is fabricated by using ion implantation and wet etching techniques to achieve, the process produced a specific pattern on lithium niobate. The chromium film and photoresist are used to wet etching and ion implantation mask respectively.By using helium ion implantation in lithium niobate crystal, it caused the lattice damage in particular depth. Then the wet etching of lithium niobate can remove the damaged area. Experimentally, we use this process to produce the micro-disk resonator device with under-cut structure. It has certain amount roughness of surface in traditional wet etching. In this study,we use two technique a short etching of proton exchange and high-temperature heat treatment. The former is the proton exchange which increase lithium niobate crystal lattice damage. To increases the lattice damage will help to accelerate the etching rate, and the roughness of substrate is first etched. The latter is close to the melting temperature of lithium niobate. The surface of lithium niobate will reflow, so the surface tension help to do some modification. If lithium niobate with high temperature the lithium oxide will out-diffusion, we have to suppress it. We placed some powder of lithium niobate to suppress lithium oxide out-diffusion in heat treatment process. We use the tapered fiber to replace optical waveguide. In this paper, taper fiber produce as electro-heating method, heat generated by arc discharge soften the fiber and it will stretch by step motor.
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Gill, Douglas Max. "Incorporation and characterization of erbium in lithium niobate." 1994. http://catalog.hathitrust.org/api/volumes/oclc/32383886.html.
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Thesis (Ph. D.)--University of Wisconsin--Madison, 1994.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 102-103).
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Yang, Shih-Yuan, and 楊詩遠. "Electro-Optic Aperiodically Poled Lithium Niobate Directional Couplers." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/22142818802512809288.
Full textAbstract:
碩士國立中央大學
光電科學與工程學系
105
In this study, we have used simulated annealing method to calculate the aperiodic domain inversion structure in LiNbO3 crystal. Moreover, we have applied this kind of structure on the electro-optically directional coupler. With the aperiodically poled LiNbO3 directional coupler (APPLNDC), it made the difference coupling result with periodically poled LiNbO3 directional coupler (PPLNDC). According to the difference arrangement of the poling structure, the directional coupler can get the difference coupling result, and thus APPLNDC can be more adjustable. In this study, our aperiodical design can make the APPLNDC get the higher fabrication tolerance, higher switched bandwidth and higher voltage tolerance. Furthermore, we fabricate the APPLNDC chip to verify our simulation result. We used our standard lithography process and Titanium diffusion process to fabricate directional coupler and the aperiodically poled LiNbO3 was made by our standard CLN(congruent LiNbO3) poling process. After the poling process, we used the E-gun and Thermal machine to fabricate the electrode. Finally, we did the cutting and the end-face polishing process, then the APPLNDC chip was ready to be measured. On the APPLNDC chip, there are different coupling length of the directional couplers. With the aperiodically poled LiNbO3, different coupling length of the directional couplers can have the same working voltage to reach crossover state at approximately 30V, and reach the straight-through state at approximately 50V. The average switched voltage is roughly 17.85V. The aperiodically LiNbO3 also can enhance the working bandwidth of the directional couplers. By our measurement, the APPLNDC can work from 1493.88nm to 1643.05nm, so the bandwidth is approximately 149.17nm. Compare to PPLNDC’s bandwidth 61.53nm, APPLNDC is 2.42 times boarder than PPLNDC. Directional coupler as an optical communication component, the bandwidth increases, the transmission capacity can also be increased, the characteristics of broadband has become a major advantage of this study. In the future, the APPLNDC can also be used to apply a coplanar waveguide electrode to modulate the light in a traveling wave, to make it a high-speed modulated optical switcher, or to further develop an integrated optical logic gate. By using the aperiodically poled LiNbO3 and then applying the high-speed modulated electrode, the electro-optically switched directional coupler will obtain more application and increase the competitiveness in the optical communication. This study have got the Best Students Poster Award in CUDOS:2017workshop. I was the second author： Hung-Pin Chung, Shih-Yuan Yang, Sung-Lin Yang, Tsai-Yi Chien, Kuang-Hsu Huang, Yen-Yu Chou, Kai Wang, Dragomir N. Neshev, and Yen-Hung Chen. “Electro-optic aperiodically poled Lithium Niobate directional couplers” CUDOS 2017 Annual workshop, Australia, Best Poster award of nonlinear quantum photonics, (2017).
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Chang, Wen-Che, and 張文哲. "Fabrication of Under-Cutting Structures on Lithium Niobate." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/2xc7v8.
Full textAbstract:
碩士國立臺北科技大學
光電工程系研究所
98
Waveguide devices with under-cutting structure on lithium niobate are produced in this thesis. By means of high index contrast of the under-cutting structure in the lateral and vertical directions, the propagating optical field can be effectively confined and the propagation loss of the curve waveguide with small radius is reduced. Under-cutting structure is formed by using ion-implantation and wet-etching techniques. In the experiments, chromium and photoresist are used as wet-etching mask and ion-implantation mask, respectively. He+ ion implantation is utilized to produce the lattice-damage region at the specified depth in lithium niobate. By the wet-etching technique, the lattice-damage region beneath the ridge structure is removed to form under-cutting structure. By using the proposed method, various waveguide devices with under-cutting structure, including straight waveguide, microring resonator, microdisk resonator, are fabricated. The effects of the fabrication parameters on the under-cutting structure are also discussed. For the fabricated microring resonators with under-cutting structure, the measured FSR is close to the theoretical one.
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Li, Zhen Hong, and 李鎮宏. "A study of improved lithium niobate optical waveguides." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/43834755996730835644.
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