Dissertations / Theses on the topic 'Q-switched'
To see the other types of publications on this topic, follow the link: Q-switched.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Q-switched.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Williams, Kevin. "Q-switched diode lasers." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296333.
Full text
2
Wang, Yuchen, Xiushan Zhu, Jie Zong, Kort Wiersma, Arturo Chavez-Pirson, Robert A. Norwood, and N. Peyghambarian. "SESAM Q-switched fiber laser at 1.2 mu m." IEEE, 2016. http://hdl.handle.net/10150/622787.
Full textAbstract:
Q-switched operation of a holmium-doped fluoride fiber laser at 1.2 mu m wavelength induced by a semiconductor saturable absorber mirror (SESAM) is reported. 650 ns pulses with 0.13 mu J pulse energy at a repetition rate of 260 kHz were obtained.
3
Lees, Gareth P. "Q-switched fibre laser sources for distributed sensing applications." Thesis, University of Southampton, 1998. https://eprints.soton.ac.uk/394390/.
Full textAbstract:
This thesis examines pulsed fibre sources for distributed sensing applications. A number of Q-switched fibre laser sources optimised for high peak powers, narrow linewidth and short pulse duration are described. The source specifications were dictated by the requirements of Raman and Brillouin distributed sensing systems. The spatial resolution of distributed sensors is related to the pulse width whereas the range is dependent on the power launched into the sensing fibre. Brillouin distributed sensors also require that the source linewidth is less than 10 GHz, the separation between the Rayleigh and Brillouin backscattered light. This constraint on laser linewidth leads to coherent Rayleigh noise on the Rayleigh backscattered trace. This noise can be reduced by a technique of frequency shift averaging. A Q-switched laser incorporating this technique was developed, which resulted in a Brillouin distributed temperature sensor with a temperature resolution of 1.4°C and a spatial resolution of 10 metres over a range of 6.5km. The development of high power Q-switched fibre lasers leads to the possibility of generating Raman shifted pulses at wavelengths of 1.64-1.65µm. Interest in this wavelength region stems from the increase in sensitivity to fibre micro-bend losses at these higher wavelengths and the ability to monitor the fibre whilst carrying out live data transmission. A diode pumped, pulsed source at 1.64µm producing 8 Watt, 10ns pulses through a process of Raman generation was demonstrated. Q-switched laser technology was also used to increase the dynamic range of 1.65µm OTDR. The technique utilised delayed Raman amplification of the 1.65µm signal pulse by a co-propagating 1.53µm pump pulse. Amplification occurs when the two pulses overlap. The position of the overlap is determined by the initial delay between the pulses and the fibre dispersion. An increase in dynamic range of 17.5dB has been observed and the 1.65µm OTDR range was extended to in excess of 100km.
4
Phelps, Charles Dustin. "Diode-Pumped, 2-Micron, Q-Switched Tm:YAG Microchip Laser." University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1304695817.
Full text
5
Zhu, Gongwen. "Q-switched and Mode-locked Mid-IR Fiber Lasers." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/578593.
Full textAbstract:
Mid-infrared (IR) lasers (2-12 μm) have found tremendous applications in medical surgeries, spectroscopy, remote sensing, etc. Nowadays, mid-IR emissions are usually generated from semiconductor lasers, gas lasers, and solid-state lasers based on nonlinear wavelength conversion. However, they usually have disadvantages including poor beam quality, low efficiency, and complicated configurations. Mid-IR fiber lasers have the advantages of excellent beam quality, high efficiency, inherent simplicity, compactness, and outstanding heat-dissipating capability, and have attracted significant interest in recent years. In this dissertation, I have studied and investigated Q-switched and mode-locked fiber lasers in the mid-IR wavelength region. My dissertation includes six chapters: In Chapter 1, I review the background of mid-IR lasers and address my motivation on the research of mid-IR fiber lasers; In Chapter 2, I present the experimental results of microsecond and nanosecond Er³⁺-doped and Ho³⁺-doped fiber lasers in the 3 μm wavelength region Q-switched by Fe²⁺:ZnSe and graphene saturable absorbers. In Chapter 3, Q-switched 3 μm laser fiber amplifiers are investigated experimentally and theoretically and their power scaling are discussed. In Chapter 4, a graphene mode-locked Er³⁺-doped fiber lasers at 2.8 μm with a pulse width < 50 ps is presented. In Chapter 5, extending the spectral range of mid-IR fiber lasers by use of nonlinear wavelength conversion is addressed and discussed. I have proposed 10-watt-level 3-5 μm Raman lasers using tellurite fibers as the nonlinear gain medium and pumped by our Er³⁺-doped fiber lasers at 2.8 μm. In the last chapter, the prospect of mid-IR fiber laser is addressed and further research work is discussed.
6
Lu, Min. "Performance of continuously pumped, passively Q-switched, solid state lasers." Thesis, University of Sussex, 2011. http://sro.sussex.ac.uk/id/eprint/6953/.
Full textAbstract:
This thesis studies the relationship between the pairs of resonator output coupling and intra-cavity absorber initial transmission, and the FWHM (full width at half maximum) pulse duration of a continuously pumped passively Q-switched solidstate laser, when the output energy is pre-determined. Depending on the magnitude of the pumping power, three different rate equation models are used to evaluate the required output coupler reflectivity and absorber initial-transmission pair for the corresponding FWHM pulse duration. The energy transfer kinetics of the passively Q-switched laser decides the required pumping power; and the pair of output coupler reflectivity absorber transmission pair, determine the build-up time of Q-switching and the repetition rate of the laser system. Hence, the forms of the models are controlled by two conditions: 1) the build-up time of Q-switching; and 2) the recovery time of the absorber. When the build-up time of Q-switching is relatively short, but the recovery time of the absorber is long, Model I is based on the simplified laser rate equations. It is used to evaluate the output coupler reflectivity and absorber initialtransmission pair, which satisfies the pre-determined output energy and FWHM pulse duration. Model II is set up to study the case when both the build-up time of Q-switching and the recovery time of the absorber are long. In Model II, the laser rate equations are solved using the Runge-Kutta method. Model III simulates the case when the recovery time of the absorber is short. To validate the models, the simulation results of practical passively Q-switched laser systems are compared with experimental results reported in the literature. The agreement of the simulation results with reported experimental results demonstrates the importance of the boundary conditions for the different cases, and verifies the soundness of the models. Generalizing the simulation results, obtained from different passively Q-switched laser systems with different pumping power and different pre-determined output energy, yields general conclusions which permit a designer to select the correct parameters for a desired laser performance.
7
Felgate, Nigel Stephen. "Efficient blue generation from all-solid-state Q-switched Nd:YAG lasers." Thesis, University of Southampton, 2002. https://eprints.soton.ac.uk/41527/.
Full textAbstract:
This thesis describes work carried out at Southampton University that has been directed towards achieving high-power all-solid-state blue sources using two low-gain transitions of Nd:YAG. Diode-end-pumping is used to obtain efficient laser performance. The thesis attempts to tackle some of the obstacles to power scaling Q-switched low-gain lasers that use diode-end-pumping schemes. A 1319nm Q-switched Nd:YAG laser is described that produces a 17KHz pulse train consisting of 353 watt peak power pulses delivering an average power of 780mW for doubling. Periodically poled lithium niobate (PPLN) is used to double to 659.5nm. A 54% second harmonic conversion efficiency produces 360mW of red average power. Sum frequency mixing of the red and infra-red in a second PPLN sample is achieved with a third order grating. A pulsed blue output (13.7 watts peak) at 439.7nm is achieved with good beam quality and an average power of 35mW. A technique is described to aid power-scaling of polarised laser sources. Analysis of the quarter wave-plate technique demonstrates that the technique will be highly beneficial in reducing the depolarisation loss in low-gain solid-state lasers. The technique is applied to a 946nm laser and a 1319nm laser. Depolarisation of the 946nm source is reduced from 1.66% to 0.0006% and depolarisation of the 1319nm laser is reduced from 1.2% to 0.015%. The quarter wave-plate technique is implemented in a high power 946nm laser that is Q-switched for low repetition rates. 0.53mJ is extracted with a 5.3KW peak pulse power at 1 kHz repetition rate. The 946nm output is used to generate 473nm blue light via second harmonic generation in non-critically phase-matched LBO at 329° centigrade. An average power of 370mW is demonstrated with a conversion efficiency of 21% at 4kHz repetition rate.
8
Paslaski, Joel Yariv Amnon Yariv Amnon. "High speed optoelectronics : photodiodes, Q-switched laser diode and photoconductive sampling /." Diss., Pasadena, Calif. : California Institute of Technology, 1990. http://resolver.caltech.edu/CaltechETD:etd-05092007-084117.
Full text
9
Rosier, Diallo Laurence. "Etude de l'endothélium cornéen par microscopie spéculaire aprés Q-Switched néodymium : Yag laser." Bordeaux 2, 1990. http://www.theses.fr/1990BOR23087.
Full text
10
Serres, Serres Josep Maria. "Continuous-wave and passively Q-switched solid-state microchip lasers in the near-infrared." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/460758.
Full textAbstract:
Aquest treball tracta de la caracterització de làsers compactes d'estat sòlid, amb un primer enfocament, l'estudi del
concepte microxip aplicat al làser en diversos hostes cristal·lins dopats amb terres rares. Es reporta els resultats sobre
l'estudi de l'efecte de thermal lens, necessari per a l'obtenció de làser amb aquesta configuració, així com pel
funcionament làser amb continu i polsat utilitzant la tècnica Q-switch.
En els experiments, el concepte microxip es defineix com una cavitat làser quasi monolítica. Aquest concepte s'estudia
per a diferents emissions de làser a ~1.06 m d'ions Yb3+ i Nd3+, a ~1,3 m de Nd3+, a ~1,95 m de Tm3+ hi ha
~2.05 m del Ho3+.
En el règim d'ona contínua s'examina detalladament per als ions de lantànids trivalents esmentats en diversos hostes
cristal·lins amb l'objectiu de comparar el potencial de cada material. En aquest treball, es demostren eficiències molt
properes al límit teòric.
D'altra banda, també es presenten làsers polsats d'estat sòlid amb la configuració microxip amb diversos absorbidors
saturables. Amb aquest propòsit, s'utilitzen com a absorbidors saturables nous nanomaterials com el MoS2, nanoestructures
de carboni (SWCNT, el grafè d'una i de diverses capes) i un SESA. A més, el més convencional Cr:YAG
(~1.06 m) i el Cr:ZnS (~1.9 m) s'examinen per comparar els seus rendiments.Este trabajo trata de la caracterización de láseres compactos de estado sólido, con primer enfoque, el estudio del concepto microchip aplicado al láser en varios huéspedes cristalinos dopados con tierras raras. Se reporta los resultados sobre el estudio del efecto de la thermal lens, necesario para la obtención de láser con esta configuración, así como para el funcionamiento láser en continuo y pulsado utilizando la técnica Q-switch. En los experimentos, el concepto microchip se define como una cavidad láser casi monolítica. Este concepto se estudia para diferentes emisiones de láser a ~1.06 m de los iones Yb3+ y Nd3+, a ~1,3 m de Nd3+, a ~1,95 m de Tm3+ hay ~2.05 m del ion Ho3+. En régimen de onda continua se examina detalladamente para los iones de lantánidos trivalentes mencionados en varios huéspedes cristalinos con el objetivo de comparar el potencial de cada material. En este trabajo, se demuestran eficiencias muy cercanas al límite teórico. Por otra parte, también se presentan láseres pulsados de estado sólido con la configuración microchip con varios absorbedores saturables. Con este propósito, se utilizan como absorbedores saturables nuevos nanomateriales como el MoS2, nano-estructuras de carbono (SWCNT, el grafeno de una y de varias capas) y un SESA. Además, el más convencional Cr:YAG (~1.06 m) y el Cr:ZnS (~1.9 m) se examinan para comparar sus rendimientos
This work deals with the characterization of compact solid state lasers, as a first approach to the study of the microchip laser concept applied to several rare earth-doped crystalline hosts. The results on the study of the thermal lens, required for the microchip laser operation as well as the continuous wave and passive Q-switched laser operation in microchip configuration are reported. In the experiments, the microchip concept is defined as a quasi-monolithic laser cavity. Such a concept is studied for different laser emissions at ~1.06 μm from Yb3+ and Nd3+ ions, at ~1.3 μm from Nd3+, at ~1.95 μm from Tm3+ and at ~2.05 μm from Ho3+. The continuous wave regime is examined in detail for the above mentioned trivalent lanthanide ions embedded in several crystalline hosts with the aim to compare the potential of each gain material. Slope efficiencies very close to the theoretical limit are demonstrated in this work. On the other hand, microchip solid state lasers passively Q-switched with several saturable absorbers are also presented. For this purpose, novel nanomaterials such as MoS2, carbon nanostructures (SWCNTs, single- and multilayer graphene) and a SESA are used as saturable absorbers. Besides, the most conventional Cr:YAG (~1.06 μm) and Cr:ZnS (~1.9 μm) are examined to compare their performance.
11
Slavinskis, Nerijus. "Short pulse q-switched longitudinally diode pumped solid state minilasers: generation, characterization and application." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110630_134119-87467.
Full textAbstract:
The dissertation is dedicated to the detailed numerical modelling of generation dynamics of actively and/or passively Q-switched diode laser longitudinally pumped solid-state lasers, characterization of spatial and temporal laser properties and for the demonstration of application possibility of created minilasers. A detailed theoretical model for the description of generation dynamics using travelling wave approach is presented. In this model more parameters of active laser medium, pump sources and resonator architecture are taken into account. In this thesis the results which show the principal difference between results obtained using the laser travelling wave model and point laser model are presented. Using point laser model the problems of generated pulse timing jitter in passively Q-switched lasers are described and its lowering possibilities using different pumping methods are suggested. In this thesis new, based by the second order moment, laser beam characterisation by knife-edge method is presented. Also laser pulse compression possibilities in tetrachloride CCL4 medium are described. It is showed that using seed signal it is possible to obtain shorter (< 60 ps) and more stable optical pulses. In this thesis application possibilities of created minilasers are presented: the experimental results of the Z-scan measurements obtained using pulses with different pulse shapes for fused silica are presented; also experiments, in which, created minilasers for paper cleaning... [to full text]Disertacija skirta diodais kaupinamų kietojo kūno lazerių su aktyviąja ir pasyviąja kokybės moduliacija generacijos dinamikos detalesnei skaitmeninei analizei, lazerio impulsų laikinių ir erdvinių parametrų charakterizavimui ir sukurtų minilazerių panaudojimo galimybių demonstracijai. Generacijos dinamikos detalesniai skaitmeniniai analizei, darbe pristatomas sukurtas bėgančiųjų bangų modelis, kuriame atsižvelgiama ne tik į daugelį procesų vykstančių lazerio aktyviajame elemente, bet ir į rezonatoriaus konfigūraciją bei kaupinimo šaltino parametrus. Pateikiami skaitinio modeliavimo rezultatai demonstruojantys šio modelio privalumus lyginant su dažniausiai naudojamu taškiniu lazerio modeliu. Naudojant taškinį lazerio modelį yra nagrinėjama generuojamų impulsų laikinio tirtėjimo problema pasyvios kokybės moduliacijos lazeriuose ir pasiūlyti mažinimo būdai naudojant skirtingus kaupinimo būdus. Darbe taip pat pateiktas naujas, antraisiais momentais pagrįstas, pluošto charakterizavimo judančiu peiliu metodas. Nagrinėjamos lazerių impulsų spūdos galimybės tetrachlorido CCL4 skystyje ir pademonstruota, kad naudojant užkrato signalą galima gauti trumpesnius (< 60 ps) ir stabilesnius optinius impulsus. Darbe pademonstruotos sukurtų minilazerių pritaikymo galimybės: aprašomas netiesinio lūžio rodiklio kvarciniame stikle matavimas Z-skenavimo metodu ir gautų duomenų apdorojimo procedūra įskaitant naudojamų impulsų erdvinę ir laikinę formą; aprašomi eksperimentai, kuriuose sukurti... [toliau žr. visą tekstą]
12
Dawson, Martin David. "Characterisation and application of a mode-locked (mode-locked/Q-switched) C.W. Nd:YAG laser." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37671.
Full text
13
Thomson, Ian James. "Efficient, high-power operation of CW Yb:YAG and Q-switched Nd:YAG planar waveguide lasers." Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2333.
Full textAbstract:
The planar waveguide gain medium o ers a good approach to creating a high- power lasers. Excellent thermal properties allow for lasers with good beam-quality and high-e ciency. A Neodymium doped YAG planar waveguide laser was actively Q-switched using a hybrid unstable resonator and acousto-optic modulator. A Yt- terbium doped YAG planar waveguide laser was side-pumped using two laser diode stacks with a total of 800 W incident pump power. The Nd:YAG planar waveguide laser has a core 200 um thick and was face pumped with ten laser diode bars. Q-switching was achieved through the use of a new hybrid unstable resonator con guration providing high-speed modulation of the laser cavity. The laser produced 100 W of average power with a pulse repetition rate of 100 kHz, giving 1 mJ pulses with 50 ns duration. Shorter 15 ns pulses were achieved with 4.5 mJ pulse energy at lower pulse repetition rates. The Yb:YAG planar waveguide laser has a 150 um core thickness, side pumped by two 430 W, six-bar diode laser stacks. Each diode stack has a custom phase- plate, correcting for collimation errors and lens aberrations. These gave a line focus matching the dimensions of the waveguide core with an incident intensity on each side of approximately 22 kWcm-2. Ray tracing of spontaneous emission within the waveguide core shows side facet angles of 7 and 20 were required to minimise ASE and parasitic oscillations within the waveguide core. A technique to image the uorescence from the Yb:YAG waveguide core has been developed. This technique allows for easy alignment of the pump lasers to the waveg- uide core and measurement of the pump intensity pro le throughout the planar waveg- uide. This technique showed single-sided pumping to follow Beer's law, and with double-sided pumping considerably improved the pump uniformity. A diode laser probe was used to measure the gain present within the waveguide. The small signal gain coe cient was shown to be 1 cm-1 with a uniform pro le across the width of the waveguide when pumped to saturation. This highlights the potential of operating the planar waveguide laser as an e cient ampli er. High-power high-e ciency operation of the Yb:YAG planar waveguide laser was achieved through the use of a hybrid stable waveguide resonator. Output power of 400 W was extracted in a multi-mode beam with a slope e ciency of 75%. This result represents the highest output power from a diode-pumped solid-state planar waveguide laser to date.
14
Kitcher, Daniel John. "Tapered gain guides in diode lasers and picosecond Q-switched bow tie laser arrays." Thesis, University of Bath, 1998. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285315.
Full text
15
Mercer, Colin. "Development of a Diode Laser Pumped Passively Q-Switched Laser Source for Range-Finding and Designating." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508559.
Full text
16
Segura, Sarmiento Martha Yamile. "Monoclinic tm:klu(w04)2: a new crystal for efficient diode-pumped continuous-wave and q-switched lasers." Doctoral thesis, Universitat Rovira i Virgili, 2012. http://hdl.handle.net/10803/80852.
Full textAbstract:
El doble tungstato cristalino de potasio y lutecio con estructura monoclínica, KLu(WO4)2, se ha establecido como una nueva matriz laser de estado sólido para iones de Tm, Yb y Ho debido a (i) las altas secciones eficaces de absorción y emisión; (ii) la relativamente larga distancia entre iones Lu-Lu permitiendo altos niveles de concentración de iones activos sin perdidas significativas por fluorescencia; y (iii) el tiempo de vida suficientemente largo del nivel emisor de la transición láser asegurando un alto almacenamiento de energía. Estas características son explotadas en este trabajo usando Tm como ion activo para generar emisión láser a 1.94 µm.
El máximo local de absorción del agua a esta longitud de onda hace a este laser interesante para aplicaciones medicas y atmosféricas. Cambio de polarización, operación en dos longitudes de onda, laser vibrónico, diseño láser de capa delgada Thin-disk, Q-conmutado pasivo y la interacción láser-tejido del láser de Tm:KLu(WO4)2 a 1.94 µm son demostrados en este trabajo.Monoclinic potassium lutetium double tungstate KLu(WO4)2 is established as new laser host for Tm, Yb and Ho active ions due to (i) its very high values of absorption and emission cross sections (ii) its relatively large Lu-Lu distances allowing high ion concentration with minimum fluorescence quenching effects and (iii) the long lifetime of the upper laser level ensuring high energy storage. These characteristics are exploited in this work using Tm as active ion to generate laser emission at 1.94 µm. The local maximum of water absorption at this wavelength makes this laser interesting for medical and atmospheric applications. Polarization switching, dual-wavelength operation, vibronic laser, thin-disk laser design, passive Q-switching and the laser-tissue interaction of the 1.94 µm Tm:KLu(WO4)2 laser are demonstrated in this work
17
Tsai, LingYi, and 蔡玲意. "Passively Q-switched intracavity optical parametric oscillator." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/85773595800845068740.
Full textAbstract:
碩士國立交通大學
電子物理系所
93
Extremely short (1.6 ns) high-peak-power (> 10 kW) pulses of lasers at the eye-safe wavelength region about 1.5 �慆 are obtained by intracavity optical parametric oscillators (OPOs). We demonstrated a compact efficient eye-safe OPO pumped by a diode-pumped passively Q-switched Nd:GdVO4 laser to produce peak powers at 1571 nm higher than 20 kW with pulse widths of 0.7ns . On the other hand, we overcome the instablility in the IOPO by using two-mirror structure .At the same time, we raise the pulse energy to 1.5 times. Due to its stability, we try to apply the two-mirror structure to tune wavelengths by temperature. As a result, we can get the curve slope about 0.4nm/0C. By the way, using Nd:Gd0.7Y0.3VO4 crystals may get 3 times the pulse energy by using Nd:YVO4 crystals and 1.8 times the pulse energy by using Nd:GdVO4 crystals.
18
Chang, Yi-Chern, and 張育誠. "Diode-pumped internally Q-switched Nd:MgO:PPLN laser." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/82224030187712634543.
Full textAbstract:
碩士國立中央大學
光電科學研究所
95
Compact and powerful diode laser-pumped solid-state lasers are of particular interest for many applications, such as laser ranging, display, remote sensing, optical storage, biomedicine, and undersea communication. Laser Q-switching technique has provided an efficient way of producing repetitively high-energy laser pulses to greatly enhance the peak power of the laser and therefore become an important technique in especially a miniature solid-state laser for producing an output power >watt level. In addition to the merit of system size reduction, monolithic integration of laser intracavity elements has the obvious advantage of reducing the difficulty with resonator loss and laser alignment. While conventional laser systems have laser gain media operated separately to other intracavity elements (e.g., the Q-switches, polarizers, nonlinear crystals, etc.), self-(internal-)Q-switching and self-frequency-doubling lasers have given good alternatives of further system miniaturization. In this work, we demonstrated the first attempt of integrating an electro-optic (EO) PPLN Q-switch in a Nd:MgO:LiNbO3 crystal to realize a compact diode-pumped internally Q-switched solid-state laser radiating at 1.085μm. We have successfully integrated a 12-mm long, 13.6-μm period EO Nd:MgO:PPLN in a 17-mm long Nd:MgO:LiNbO3 laser gain medium. When the EO Nd:MgO:PPLN Q-switch was driven by a 5 kHz, 260-V voltage pulse train with a 300 ns pulse width, at 0.61-W absorbed pump power, we measured ~7.7 mW average power or 55 W peak power with 1.6-μJ pulse energy in ~30-ns laser pulse width. Since PPLN is characterized by its flexibility of structure tailoring for phase-matching an arbitrary nonlinear wavelength conversion process, the extension of currently developed internally Q-switched Nd:MgO:PPLN laser to a monolithic all PPLN internally Q-switched intracavity wavelength converter is promising.
19
Yen-ChengFang and 方彥程. "All-fiber self Q-switched fiber laser." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/60141711939221725072.
Full textAbstract:
博士國立成功大學
微電子工程研究所碩博士班
98
The purpose of this dissertation is to propose and demonstrate self Q-switched all-fiber erbium laser systems, using three novel techniques local intensity-enhancement in a ring resonator, mode-field mismatching in a standing-wave resonator, and lifetime-shortening with an auxiliary laser source. A saturable absorber Q-switched all-fiber ring laser is first realized. By locating a saturable-absorber fiber in the intensity-enhanced section of a ring resonator, an all-fiber laser is passively Q-switched. The design has been numerically and experimentally demonstrated using Er3+-doped fiber at the emission wavelength of 1550 nm. A single-mode Q-switched pulse with pulse energy of 0.37 μJ and pulse duration of 218 ns was achieved with 980-nm pump power near 7 mW. In addition, a self Q-switching method using mismatched mode field areas and a saturable-amplifier pump switch are successfully demonstrated for sequentially generating Q-switched pulses. This is a fully passive, all-fiber Q-switched laser system. Pumped with a continuous-wave (CW) 980-nm laser diode (LD), sequential pulses with a pulse energy of 8–6 μJ and a pulse duration of 80-320 ns, corresponding to a pulse repetition rate of 0.25-1 kHz, were obtained. A peak pulse power of near 100 W was achieved. Furthermore, a technology of increasing the recovering rate of the saturable absorber using an auxiliary laser source is demonstrated. Through the use of an auxiliary 1570-nm laser that shortened the relaxation lifetime of erbium, sequentially Q-switched pulses with pulses energies between 4 and 6 μJ and pulse widths of 40 ns were achieved. A peak power of 165 W was obtained.
20
yu, Hsu shang, and 徐尚聿. "Dual color actively Q-switched Nd:GdVO4 laser." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/61450046647120946031.
Full textAbstract:
碩士逢甲大學
光電學系
101
The purpose of this thesis is to construct an actively Q-switched, dual color selectable Nd:GdVO4 laser by using a cascaded electro-optic periodic poled lithium niobate Bragg modulator (EPBM). The cascaded EPBM integrates Q-switching and wavelength selector monolithically. By controlling the voltage of EPBM, we can Q-switch and select the output wavelength between 1063 and 1342 nm. Adopting intracavity second harmonic generation, dual color between green (531.5 nm) and red (671 nm) are also generated. At 24 W diode power, and 1 kHz repetition rate, we generated 314 and 99.7 μJ pulse energy at 1063 and 1342 nm, respectively. We also changed the repetition rate 5, 10, 15, and 20 kHz, respectively. Due to the broad bandwidth of EPBM2, we can Q-switch two wavelength (1063 nm and 1342 nm) simultaneously. Varying the DC voltage of EPBM1, we can selectively generate 1063 nm (-300 V) and 1342 nm (0 V) with pulse energy 60 and 65 μJ, respectively. After the frequency doubling process we generated 174.2 and 32 μJ pulse energy at 531.5 and 671 nm, respectively at 24 W diode power, and 1 kHz repetition rate.
21
Lin, Che-Yung, and 林哲雍. "Active Q-switched Erbium Doped Fiber Laser." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/3xfkre.
Full textAbstract:
碩士國立臺北科技大學
光電工程系所
94
In this work, an active Q-switched erbium doped fiber laser is studied. In the experiment, the linear and the ring structures of the laser cavity are used, and the electro-optic and acousto-optic modulators are utilized as the Q-switch. After comparing three fiber laser structures, the high-peak power Q-switched fiber laser adopts the linear laser cavity formed by the reflection mirror with high reflectivity at 1550nm and the perpendicular fiber end. In the pulse compression process, the acousto-optic modulator is used as the Q-switch to produce the pulse with short duration. In the experiments, the effects of pump power, pulse repetition rate, high-Q duty cycle, and erbium-doped fiber length, on the pulse peak power and pulse duration, are discussed. Experimental results show that high pump power, low repetition rate, and short high-Q duty cycle facilitate the enhancement of pulse peak power and reduction of pulse duration. Under the condition of optimal pulse peak power (high repetition rate), the pulse with peak power of 810W (718W) and pulse duration of 30ns (45ns) is produced in the erbium doped fiber laser using erbium doped fiber length of 2.25m with repetition rate of 0.3kHz(1kHz) and pump power of 400mW.
22
Chen, You-Ming, and 陳又銘. "Diode-pumped hybrid Q-switched narrow linewidth laser." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/apr5zm.
Full textAbstract:
碩士逢甲大學
光電學系
104
In this thesis, a hybrid Q-switched Nd:YVO4 laser at 1064 nm with narrow linewidth, linear polarization, and high repetition rate was constructed. Hybrid Q-switched configuration combines the advantages of passive Q-switch scheme including short pulse duration and narrow linewidth, and active Q switch scheme including stable repetition rate and low timing jitter. To generate a single longitudinal mode pulsed laser, we adopted volume Bragg grating as the output coupler, and twisted-mode technique to eliminate spatial hole burning in the gain medium. At a diode pump power of 20 W, we demonstrated a hybrid Q-switched, single longitudinal mode Nd:YVO4 laser producing single-longitudinal-mode linewidth of 270 MHz, 12.2 ns, 124 μJ pulses at 33 kHz repetitions.
23
Huang, Wen-Cheng, and 黃文政. "The study of passively Q-switched fiber lasers." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/98537971233131679287.
Full textAbstract:
博士國立交通大學
電子物理系所
102
The double-cladding Yb-doped fiber as the gain medium and the passively Q-switching technique have been utilized in study of high power and high-repetition rate fiber lasers. First we use the double-cladding fiber with core diameter of 30 μm, and the AlGaInAs semiconductor material and the Cr4+:YAG crystal are used as the saturable absorbers (SA) respectively. By using the AlGaInAs as the SA, pulse energy up to 0.45 mJ with the repetition rate of 30 kHz in the pump power of 24 W can be attained. With the Cr4+:YAG crystal as the SA, we can have the laser output with a pulse energy of 0.35 mJ at the pulse repetition rate of 38 kHz in the same pump power. We also have comparative studies between these two SAs. For scaling energy further, the photonic crystal fiber (PCF) with the core diameter of up to 70 μm is used as the gain medium. With the AlGaInAs as the SA, the pulse energy is significantly increased 2.4 times to 1.1 mJ, and the shorter cavity length results in the pulse width reducing from 60 ns to 10ns. As a sequence, the peak power is boosted up from 7.5 kW to 110 kW. This scheme is also used for pumping the extracavity optical parametric oscillator (OPO), and the output energy of 138 μJ with the repetition rate of 6.5 kHz at the wavelength which can be tunable from 1513 nm to 1593 nm is obtained. By employing the Cr4+:YAG SA, the pulse energy also has almost 2-times enhancement to 0.63 mJ and the pulse width decreases from 70 ns to 36 ns. An intracavity OPO was demonstrated based on this scheme, output power of 0.47 W at 1515 nm was obtained. To achieve higher peak power, it is necessary to have smaller pulse width, so we adopt the configuration of master oscillator fiber amplifier (MOFA). By using a Nd:YVO4/ Cr4+:YAG passively Q-switching laser as the seed laser and a 30-μm-core double-cladding fiber as the amplifier, the amplifier can generate pules with energy of 0.192 mJ at the repetition rate of 25 kHz and the pulse width is down to 1.6 ns. In addition, a PCF MOFA was used to pump the extracavity nonlinear wavelength conversions module, output powers of 1.7 W of the second harmonic generation at 532 nm and 1.1 W of the third harmonic generation at 355 nm were realized at the fundamental pump power of 3.3 W.
24
Huang, Yi-Hao, and 黃益豪. "High Peak-Power Active Q-Switched Fiber Laser." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/dr87g8.
Full textAbstract:
碩士國立臺北科技大學
光電工程系研究所
95
In this work, an active Q-switched erbium-ytterbium co-doped double cladding fiber laser is studied. In the experiment, the linear cavity structure is used and the acousto-optic modulator is utilized as a Q-switch. The high-peak power Q-switched fiber laser adopts the linear cavity formed by the reflection mirror with high reflectivity at 1550nm and the perpendicular fiber end. In the pulse compression process, the acousto-optic modulator is used as the Q-switch to produce the pulse with short duration. This studies uses three kind of erbium-ytterbium co-doped double cladding fiber as gain medium. The effects of pump power, pulse repetition rate, and erbium-doped fiber length on the pulse properties, including pulse peak power and pulse duration, are discussed. Experimental results show that high pump power and low repetition rate facilitate the enhancement of pulse peak power and reduction of pulse duration. Under the condition of optimal pulse peak power, the pulse with peak power of 22.69kW and pulse duration of 13ns is produced in the active Q-switched fiber laser using erbium-ytterbium co-doped large-mode-area double cladding fiber length of 9m with repetition rate of 0.1kHz and pump power of 7W.
25
Tsai, Ming-Chen, and 蔡明辰. "Investigation of orthogonally-polarized passively Q-switched lasers." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/4fayr5.
Full textAbstract:
碩士國立交通大學
電子物理系所
106
The aim of this thesis is to study the influences of birefringence effect of gain crystal on the output polarization states for the passively Q-switched (PQS) orthogonally polarized lasers. Considering the stress-induced birefringence to the isotropic gain crystals, we firstly compared the temporal dynamics of the orthogonally polarized pulse trains of the Nd:YAG and c-cut Nd:YVO4 PQS lasers . Experimental results reveal that the two orthogonally polarized states of the Nd:YAG PQS laser will exhibit regular energy switching behavior in the pulse trains, whereas the pulse trains of the c-cut Nd:YVO4 laser present comparatively random switching dynamics between the orthogonally polarized states. In order to further explore the switching behavior of the orthogonally polarized states in the PQS pulse trains under different levels of the stress-induced birefringence, the temporal dynamics of a monolithic Nd:YAG/Cr4+:YAG PQS laser was studied considering different pumping conditions. Experimental observations show that the period corresponding to the polarization switching in the PQS pulse trains is highly correlated with ratio of the lasing longitudinal mode numbers for the orthogonally polarized components. We expect the experimental finding can be applied to the realms of optical remote sensing and optical communication and so forth.
26
Chang, Wei-Kun, and 張煒堃. "Pulsed orange, green, and red laser generations in an actively Q-switched Nd:YVO4 laser using cascaded electro-optic PPLN Q-switches." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/asva39.
Full textAbstract:
碩士國立中央大學
光電科學研究所
97
Intracavity frequency doubling in an Nd-laser system has become one of the most efficient methods of producing blue, green, and red coherent lights. However, no practical laser sources yet currently available in the yellow-orange (570-620-nm) spectral region, nor applicable fundamental infrared lasers for performing efficient frequency doubling to the region. Sum frequency generation (SFG) of two emission lines from transitions 4F3/2 – 4I11/2 (?1~1.06 ?m) and 4F3/2 - 4F13/2 (?2~1.3 ?m) of Nd-lasers has become an important approach of generating coherent radiation in the yellow-orange spectral region. Compact, high-repetition-rate pulsed visible coherent light sources are attractive for many applications such as bio-medicine, remote-sensing, astronomy, and military. We achieved in a collinear three-mirror dual-wavelength Nd:YVO4 laser system using two monolithically cascade electro-optic (EO) periodically poled lithium niobate (PPLN) Q-switches to separately control the Q-switching operation of the two wavelengths to optimize the temporal overlap between them for efficient pulsed intracavity sum-frequency generation. With this novel system, we can generate 5 high peak-power and high repetition-rate lasers radiating at Nd:YVO4 1064- and 1342-nm lines and their non-phase-matched SHG 532- and 671-nm light and their phase-matched SFG 593-nm light via the manipulation of the Q-switching operations of the 3-cm bulk EO PPLN Q switches. We found a pulse build-up delay time of ~25 ns between the two pump wavelengths is required for achieving the best SFG efficiency in our system. When the system is operated at a repetition rate of 1 kHz and a pump power of ~5W, we obtained pulsed orange (593 nm), green (532 nm), and red (671 nm) generations with peak powers of 140, 20.6, and 8.6 W, respectively.
27
Chen, Li-Hsuan, and 陳立宣. "The study of passively Q-switched Yb:YAG ring laser." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/16847395367843408048.
Full textAbstract:
碩士國立中山大學
光電工程研究所
94
Compared with Nd:YAG, the traditional high power solid state laser gain medium, Yb:YAG has less quantum defect, no excited state absorption, and longer fluorescence lifetime, which makes it suitable for Q-switched laser. In addition, concentration quenching is absent in Yb:YAG, higher concentration of active ion makes the thickness of gain medium thinner. For ring cavities, the necessity of symmetrical beam path is important, a thinner Yb:YAG crystal can reduce the shift of optical beam path and avoids cavity unstability. Thus, Yb:YAG is suitable for the two-mirror ring cavity. In this study, a compact and efficient Yb:YAG ring laser with 50.3% slope efficiency was demonstrated. And the Yb:YAG ring laser performances influenced by thermal effect was analyzed and compared to that of Nd:YAG ring laser. The polarization of ring lasers with different configurations were also discussed. In manufacturing process, the coating design on gain medium and laser mirrors were introduced. The advantages of passively Q-switched laser are efficient, compact, simple setup and no complicated driving circuits. They make passively Q-switched laser suitable for various applications, such as nonlinear optics, medical treatment, micromachining, material processing, and range finder. Due to spontaneous noise from the gain medium, conventional passively Q-switched laser has large timing jitter. This study is to build up a passively Q-switched Yb:YAG/Cr4+:YAG ring laser with lower timing jitter. At present, a Q-switched ring laser with a peak power of 208 W and a pulse width of 33 ns, was developed. Its slope efficiency is 18.1% with a timing jitter of 11.9%. To our knowledge, this is the first passively Q-switched Yb:YAG/Cr4+:YAG ring laser.
28
Weng, Yi-Lung, and 翁義龍. "Intracavity Frequency-Doubled and Passively Q-Switched Blue Laser." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/71879682231142160516.
Full textAbstract:
碩士國立中山大學
光電工程研究所
88
The purpose of this study is to develop a solid-state blue laser which has advantages of high power, short wavelength, and compact. It can be applied in micromaching, LIDAR, underwater ranging, biochemical techniques, and so forth. We increased the peak power of the laser effectively by a low-cost, small, and easy-use passive Q-switching technique. In addition, intracavity frequency-doubling is an economic way to achieve non-linear frequency conversion for blue generation. By integrating of these two techniques, we develop a compact all solid-state high-power blue laser with 83 W peak power at 473 nm. Restricted to reabsorption loss, the optical to optical conversion efficiency of 4F3/2 → 4I9/2 quasi-three-level laser is lower than 4F3/2 → 4I11/2 four-level laser for Nd:YAG crystal. The reabsorption loss will change with the temperature variation of the gain medium, it enormously affects to the performance and stability of quasi-three-level lasers. Therefore, in addition to make systematic studies of the conversion efficiency of KNbO3, BBO, LBO as the intracavity SHG crystals for generation of high-power blue laser, we use the numerical analysis to investigate the influence of reabsorption loss to quasi-three-level passive Q-switching laser. At present, blue laser with peak power of 83 W and pulse width of 10.6 ns was generated as a result. To our knowledge, the compact all solid-state high-power pulsed blue laser is demonstrated for the first time by integrating of passive Q-switching and intracavity frequency-doubling simultaneously.
29
Fan, Shin-An, and 范信安. "Study of All Fiber Passively Q-Switched Pulses Laser." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/18202805653536288799.
Full textAbstract:
碩士中原大學
應用物理研究所
95
An all-fiber passive Q-switched pulsed laser has been established and its performance has been investigated. The laser system was configured by using a Samarium (Sm)-doped fiber as saturable absorber, a Yb3+-doped double cladding fiber as the gain medium, and a Bragg-fiber gratings as the optical cavity. In the past, most of the Q-switched fiber lasers are consist of bulky elements that normally invoke sophisticated designs and are usually drawback by incompactness. Here, the conventional crystal saturable absorber was replaced by a Sm-doped fiber, making this pulsed laser as a genuine all-fiber Q-switched laser. In addition, a Yb3+-doped double cladding fiber was also adopted in the system to improve its coupling efficiency and output power. In the preliminary test, a pulse energy of 202 nJ, repetition rate of 50 kHz have been shown. The present optimized results, the pulse width of 0.9μs, and with a peak power of 224.4 mW at center wavelength of 1086.44 nm and a FWHM bandwidth of 1 nm were achieved. The effects of pumping optical source power on the output power, repetition rate, and pulse energy were also investigated. It was found that the higher the pumping power, the higher the output power and pulse energy, but the lower the repetition rate.
30
Hsieh, Cheng-Lu, and 謝政陸. "Optimization of Active Q-switched Lasers at 532 nm." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/thtc27.
Full textAbstract:
碩士國立交通大學
理學院應用科技學程
105
The aim of this thesis is focused on developing reliable active Q-switched lasers at 532 nm based on linear cavity configuration. First of all, we demonstrate the influence of cavity configuration on the Q-switched pulse shape by using different front mirrors. Experimental results reveal that convex-plano cavities are the most suitable cavity design to obtain short pulse width and excellent pulse shape. Moreover, based on convex-plano cavities, we utilize different radii of curvature of front mirrors to explore the performance of laser output. We experimentally find that the suitable pump power range is strongly dependent with the radius of curvature of front mirror. The larger radius of curvature of front mirror, the lower suitable pump power. Finally, we explore that pulse-to-pulse stability depends on the performance of phase locking between longitudinal modes. Preliminary results show that the performance of phase locking is independent with the radius of curvature of front mirror. This work not only enables us to realize reliable active Q-switched lasers at 532 nm, but also offers some important insights for Q-switched lasers at different output powers.
31
Chiou, Jhao-Ren, and 邱昭仁. "Diode-pumped Continuous-waved EO Q-switched Tm:YAP laser." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/7h6ryn.
Full textAbstract:
碩士逢甲大學
光電學系
106
The purpose of this thesis is to construct a diode-pumped high power wavelength tunable Tm:YAP laser in the 2μm range. We utilize two schemes, gain switching and EO Q-switching, to generate pulsed laser and compare the output performance. We first construct a continuous wave Tm:YAP laser with more than 8 W output power and 45.7% slope efficiency when the cavity length and diode wavelength were 25 mm and 792 nm, respectively. By adjusting an intracavity quartz birefringent plate, the output wavelength of Tm:YAP laser can be tuned from 1933 to 1998 nm. Pulsed Tm:YAP laser was then generated through gain-switching and quasi cw pump scheme. When pump peak power was 38 W and pump pulse duration was 510 μs, the pulse energy, pulse duration and pulse repetition were 189 μJ, 1.34 μs and 500 Hz, respectively. Q-switched Tm:YAP laser was constructed through EO MgO:PPLN. When pump power was 18 W, the pulse energy, pulse duration and pulse repetition were 2.25 mJ, 43.6 ns and 200 Hz, respectively.
32
Lin, Yung-Hsiang, and 林泳詳. "Study of Passively Q-switched Lasers with Volume Bragg Grating." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/62045743617257417877.
Full textAbstract:
碩士國立清華大學
光電工程研究所
96
In this thesis, the theory of Passively Q-witched Laser will be discussed in detail. A Volume Bragg Grating (VBG) was used to eliminate longitudinal mode in cavity. The gain medium was Nd:GdVO4 with 1% Nd doped and the saturable absorber was Cr:YAG. There were four laser systems finished step by step including (1) CW laser generation with linear cavity (2) passively Q-switched laser generation with linear cavity (3) CW laser generation with V-type cavity (4) passively Q-switched generation with V-type cavity. VBG was used in the third and the fourth system to compare with the first and the second system which without VBG. Another saturable absorber Cr:YVO4 was used to try to build a passively Q-switched laser.
33
Yang, Yeon-Lung, and 楊永隆. "Resonator-Configuration-Dependent Dynamics of Passively Q-Switched Nd:YAG Lasers." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/94664830333313182216.
Full textAbstract:
碩士東海大學
物理學系
92
In this thesis, we experimentally study the resonator-configuration dependent dynamics in an axially pumped passively Q-switched Nd:YAG laser with a plane-concave cavity. We observed the average output power, repetition rate and pulse width as a function of the cavity length at different pump power. Our investigation shows that the laser pulse train will fall into unstable when the cavity length is adjusted near the edge of the geometric stable resonator configuration. We also find that the laser tends to run into multiple transverse modes in this region. Therefore,the instability of Q-switched pulses is related to the interaction of multiple transverse modes around the hemispherical resonator configuration where they are subject to a significant cavity-length-dependent variation of gain or loss.
34
Chang-ChingTsai and 蔡長青. "Passively Q-switched all-fiber laser at high peak power." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/54336188897487780061.
Full textAbstract:
碩士國立成功大學
微電子工程研究所
104
This thesis focused on simulation of Q-switched pulsed laser and implement the passively all- Yb+3fiber Q-switched pulsed laser at high peak power using mode-field area mismatch method in dual cavity. Since the output power of single-mode laser diode is too low，we use multi-mode laser and cladding pumped laser system to boost the output power of laser system and achieve the high power Q-switched all-fiber laser system. We also derive some theories about mode-field mismatch method and rate equations about dual cavity. Based on the outcome in the chapter2，we establish a numerical model to simulate a Q-switched pulse. In the simulation，we get a Q-switched pulse with an energy of 38.64 μJ、a width of 32.83 ns and a peak power of 975W. Moreover, the performance of pulses can be improved by replacing the longer SAQS fiber in the experiment. The tendency observed in the experiment provide a clear direction to optimize the pulsed laser system in the future.
35
Te-LunYen and 顏德倫. "Study on 1590-nm passively Q-switched all-fiber laser." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/m9ww3x.
Full text
36
Zhong, You-Sheng, and 鐘祐笙. "Self Q-switched Mode-locking in a diode-pumped Nd：YVO4 laser." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/20905780920602569696.
Full textAbstract:
碩士東海大學
物理學系
89
We found self Q-switched mode locking can occur in a low power free running Nd：YVO4 laser without additional switch element inserted in a plane-plane cavity except for a lens and a gain medium which is end pumped by a diode laser. Spontaneous giant spike takes place when the cavity configuration is adjust near the border of stability region where the beam spot size is shrink on the plane mirrors and diverge on the lens. Stable pulses with pulse width of 100-400 ns and repetition rate of 150-600 KHz for Q-switching as well as pulse width of 250-400 ps and repetition rate of 250-500 MHz for mode-locking have been generated in the experiment under pump power range from 240 to 800 mW. The self Q-switched mode locking is associated with Kerr lens effect in Nd：YVO4 crystal to reduce diffractive loss introduced by finite aperture of the lens.
37
Madlala, Bigboy. "Designing a low cost passively Q-switched solid state laser transmitter." Thesis, 2017. https://hdl.handle.net/10539/24990.
Full textAbstract:
A dissertation submitted to the Faculty Of Science in partial fulfilment of the
requirements for the degree of
Master of Science by research only
in the School of Physics, University of the Witwatersrand, Johannesburg. July 11, 2017.A discrete Q-switched laser that gives a side-lobed single pulse as a laser output was implemented; followed by studying energy extraction e ciencies and pulse characterisation. The aim was to help design a passively Q-switched laser that gives a smooth single pulse of optimum energy as a laser output. The smoothness feature in a single pulse is important in some applications such as range nding. The concepts are demonstrated both experimentally and numerically; the latter using Fox-Li approach to modeling resonator modes with the Fresnel's integral for the system under study. In the rst two chapters, fundamentals of how a laser works and the spatial mode development are studied. In chapter 1, the principles of a laser are discussed: absorption, spontaneous and stimulated emission. Also, di erent types of pumping sources and resonator con gurations that can be used are discussed. In chapter 2, the focus is on developing spatial modes of a laser. The fundamental and high order modes are discussed together with their propagation laws. Then a numerical method is used to nd the eigenmodes of an arbitrary resonator con guration. This numerical method is used to simulate propagation of a fundamental mode and the simulation results are compared to analytical propagation laws. Then, this numerical method is used to simulate a laser resonator. The eigenmode of the lowest loss in the resonator was found. In chapters 3 and 4, experimental work is done on a Q-switched laser where the focus is on the overall laser performance. In chapter 3, Q-switched laser output energies are studied for di erent combinations of Q-switch transmission values and output coupler re ectivities. In addition, the in uence of spatial modes on a Q-switched pulse shape and pulse width are studied, taking into account beam divergence. In chapter 4, conclusions and future work are presented. In future work, the knowledge of spatial mode in uence on pulse shape, pulse width and beam divergence from chapter 3 is exploited. Then particular resonator con guration that gives optimised output results (Q-switched laser output energy, beam divergence, pulse shape and pulse width) is chosen. On that particular resonator, di erent Q-switch transmission values are studied, but now looking only at beam divergence and pulse width. Also, some suggestions on further improving laser performance are given.
LG2018
38
Chen, Yi-chun, and 陳怡君. "Spatial and temporal behavior in diode-pumped passively Q-switched laser." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/8t4y2h.
Full textAbstract:
碩士國立交通大學
電子物理系所
92
We can obtain high peak power laser with absorber inside cavity. High peak power lasers are applied to distance measuring, radar, medical system and industry marker process. The lasers which are used to be the distance measuring tools has a series pulse delay problem. In our thesis, we will discuss that the transverse modes of different cavities and the variation of pulse delays of different mode position. Delay in pulse arrival times from hundreds of picoseconds to several tens of nanoseconds can be observed in our experiment.
39
Huai-MinHuang and 黃懷民. "Full-band passively Q- and gain-switched Yb3+ all-fiber laser." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/99486101101667485629.
Full textAbstract:
碩士國立成功大學
微電子工程研究所碩博士班
98
The purpose of the study is to produce a passively pulsed Yb3+ all-fiber laser that self-balances between being Q-switched at 0.97-0.98 μm and being gain-switched at 1-1.12 μm, using a continuous-wave 915 nm pump laser diode. The device was experimentally demonstrated at 976 nm of Q-switching, and 1064 nm of gain switching. With pump power of 110 mW, a single-mode Q-switched pulse at 976 nm with pulse energy of 1.5 μJ and pulse duration of 275 ns was achieved. Furthermore, the rate equations to simulate the interactions between the dual-wavelength photons and the populations of the ytterbium gain and absorber fibers were established. With desirable fiber Bragg gratings, a CW-pumped Yb3+ laser can produce sequential pulses in the ytterbium emission band of 0.97-1.12 μm.
40
Liao, Chien-Hsun, and 廖建勛. "Pump and cavity effects in a passively Q-switched Nd:YVO4 lasers." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/23300563772634102279.
Full textAbstract:
碩士東海大學
物理學系
96
In this thesis, we experimentally study pump and cavity effects in passive Q switching of diode-pumped a-cut and c-cut Nd:YVO4 lasers. The average output power, pulse width, and period were measured as functions of the pump spot size and resonator configuration. Our investigation shows that larger pump spot size is favorable for good Q switching. Suppression and enhancement effects on passive Q switching were observed near the border of geometrically stable resonator figuration. We also find that c-cut Nd:YVO4 crystal is a more preferable gain medium than a-cut one for generating short pulse width, high peak power, and stable Q-switched pulses. Based on these studies, the generation of Q-switched pulses with pulse width as short as 26 ns and peak power up to 150 W were achieved by use of a c-cut Nd:YVO4 crystal under pump power of 890mW.
41
Tsung-Yuan, Tsui, and 崔宗元. "The Study of the Passively Q-Switched Nd:YAG/Cr4+:YAG Laser." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/56366526211591825702.
Full textAbstract:
碩士國立中山大學
光電工程學研究所
86
Passively Q-switched laser is the most simple and economic one in all kinds of Q-switched lasers. Dye has been used in passively Q-switched laser as satur-able absorber, but bleaching and deterioration make it trouble for frequent re-placing, and there is no way for direct control of the pulse repetition rate.T- iming jitter is a serious problem for this type of laser. In this thesis, a diode-laser-longitudinally pumped Nd:YAG/Cr4+:YAG Q-swi-tched laser is studied. Cr4+:YAG is a good saturable absorber for passively Q-switched laser because of its good material quality and high damage threshold(500MW/cm2).We tried 2 different laser cavity structures for this kind of laser, half-symmetry and miniature. For the half-symmetry laser cavity, the best re-sults we achieved for pulse width, peak power and pulse energy are about 15 ns,11.4 KW and 0.2 mJ respectively; and for the other one, they are 4 ns, 21 KW and 0.091 mJ. To the best of our knowledge, pulse energy for both laser cavity are the largest for longitudinally diode pumped Nd:YAG/Cr4+:YAG laser. Timing jitter is a very serious problem in a passively Q-switched laser. Alot of theoretical works have been done on the optimization of the peak power and pulse width. In this thesis, a model is constructed for analyzing this pro-blem numerically. In the experiment, 41% timing jitter improvement on half-sym-metric laser cavity is done by external modulation on Cr4+:YAG using a laser d-iode.
42
Paslaski, Joel Stephen. "High Speed Optoelectronics: Photodiodes, Q-Switched Laser Diode and Photoconductive Sampling." Thesis, 1990. https://thesis.library.caltech.edu/1706/1/Paslaski_j_1990.pdf.
Full textAbstract:
In this thesis, a variety of topics related to high speed optoelectronic devices and measurement techniques using ultrafast optical pulses are presented.
Following a brief introduction, the second chapter describes a Q-switched semi-conductor laser using a multi-quantum well active layer both for gain and as an intracavity loss modulator. While Q-Switching does not produce as short a pulse as modelocking, it does offer the advantage of adjustability of the repetition rate making it attractive as a source for digital communication links. It is also found to be preferred to the similar approach of gain switching due to less demanding requirements on the rf modulation power level and waveform. Results include a pulse width of ~ 20 ps which is fairly independent of the repetition rate, and a limiting repetition rate of 3.2 GHz. The onset of an irregular pulse train which limits the maximum modulation frequency, is analyzed by a graphical approach.
The potential for optical interconnects has motivated a marriage between the two technologies of Si VLSI and GaAs optoelectronics. Direct integration by the growth of GaAs on Si had been impossible, but the MBE and MOCVD techniques now enable the growth of such layers and of a quality suitable for devices. The third chapter describes the operating characteristics of GaAs-on-Si lasers and photodiodes with particular attention to their high speed performance. Both the lasers and photodiodes show comparable high speed performance to similar structures fabricated on GaAs, with most of the shortcomings being in their dc characteristics.
In the fourth chapter, a novel approach to improving the resolution of photoconductive sampling is presented, called differential sampling. This technique obviates the need for carrier lifetime reduction usually used to improve temporal resolution, and is in principal only limited by a small (few ps) RC circuit time. An analysis of the minimum detectable signal voltage shows the technique does quite well compared with lifetime reduction techniques which also tend to reduce mobility and dark resistance. An experimental demonstration of this technique is presented in chapter five. Using a two gap sampler, accurate measurement (10 ps resolution) of a 60 ps pulse response from a photodiode is achieved using photoconductors with a recovery time of only 150 ps. Performance near the fundamental Johnson noise limit is also attained, though the minimum detectable signal is higher than predicted due to low response of the photoconductors (probably due to poor contacts).
Finally, in chapter six, the possibility of retrieving an impulse response from its autocorrelation is explored. The use of the logarithmic Hilbert transform for phase retrieval has been discounted in the literature since most such work is concerned with imaging problems for which it is not appropriate due to their symmetric nature. However, causality and the decay nature of transient phenomena make this technique very suitable for use with the impulse response of passive devices. Conditions for the validity of this technique for temporal problems are presented. Simulated retrieval of two functions with similar autocorrelations is demonstrated with sufficient clarity to distinguish them, as well as showing good agreement with the original. Practical limitations and aspects -- such as noise, finite time domain, etc. -- are also simulated and discussed.
43
Yen, Tzu-Hsiang, and 顏子翔. "Stable Q-switched mode-locked Yb-fiber laser by AO modulation." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/23551003944178131102.
Full textAbstract:
碩士國立交通大學
光電工程系所
97
In this thesis, reliable Q-switched mode-locking in an Yb-doped fiber laser is demonstrated by employing an acousto-optic modulator (AOM) and a linear fiber cavity. Within the Q-switched envelope, mode-locked pulses with the repetition rate of 40 MHz can be obviously seen and their repetition rate is equal to the RF driving frequency of the AOM. In our experimental observation, the width and the asymmetry ratio of the Q-switched envelopes depend on the modulation frequency of AOM. At lower modulation frequencies, satellite pulses can be seen with their number being also related to the modulation frequency of AOM. By alternation the optical focus spot size on the AO crystal, we demonstrate that the amplitude modulation of the AOM plays the dominant role for starting the harmonic mode-locking of the laser.
44
Dong-LinLi and 李東霖. "Radial and azimuthal polarizations in passively Q-switched solid-state laser." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/73158684348863903295.
Full textAbstract:
碩士國立成功大學
光電科學與工程學系
101
Radially and azimuthally polarized beams were generated in passively Q-switched Nd:GdVO4 laser with a Cr:YAG saturable absorber. Based on the cavity design, the cavity configuration simultaneously satisfied the thereshold of the passive Q-switching and the generating condition of the cylindrical vector beam. When the pump power was 5W, the pulse width, repetition frequency, and the average power were 110 ns, 12.3 kHz, and 270 mW, respectively. The pulse operation had better polarization ratio than that of continuous-wave operation. Moreover, the spatial-dependent pulse trains were explored, and the dynamical behavior is an interesting future work.
45
Huang, Kuan-Hao, and 黃冠皓. "Q-switched and mode-locked pulse generation from ytterbium doped fiber." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/4vs5e2.
Full textAbstract:
碩士國立臺北科技大學
光電工程系研究所
104
In this work, I investigated the Q-switched and mode-locked pulse generation in all-normal dispersion passively mode-locked Yb-doped fiber laser (PML-YDFL) based on the Bi2Se3/Polyvinyl alcohol (PVA) film or fiber-compatible topological insulator saturable absorber (TI-SA). First, we synthesized the Bi2Se3 nano-plates (NPs) via a polyol method and then dissolved the PVA into Bi2Se3 solution to produce the Bi2Se3/PVA solution. Through the drying of the Bi2Se3/PVA solution in standard cell within the oven, the dark and light Bi2Se3/PVA films were produced with high and low transmittance. After insertion the dark Bi2Se3/PVA films into an Yb-doped fiber laser laser (YDFL), the Q-switched pulse can be generated after properly adjusting of the polarization controller. As pump power increased from 105 to 182 mW, the repetition rate of Q-switched pulses was increased from the 86 KHz to 138 KHz. In addition, the mode-locked pulses with 16 MHz repetition rate and the shortest pulsewidth about 380 ps were demonstrate through the light Bi2Se3/PVA film with the pump power at 380 mw. We also fabricate the fiber-compatible TI-SA by depositing the Bi2Se3 NPs onto the fiber end facet. In comparing to the PVA film, the PML-YDFL can be mode locking at lower threshold power and higher slope efficiency. With the pump power at 131 mw, the mode-locked pulses with 13 MHz repetition rate and the shortest pulsewidth about 331 ps were demonstrate through the fiber-compatible TI-SA. Our experimental results indicate that the TI-SA made by the Bi2Se3 can be exploited for the pulsed laser applications.
46
Wang, Hsing-Kai, and 王星凱. "Optimization of Active Q-switched Lasers at Wavelength of 671 nm." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/6nub8d.
Full textAbstract:
碩士國立交通大學
理學院應用科技學程
106
The aim of this thesis is focused on developing reliable active Q-switched lasers at 671 nm based on linear cavity and V-shaped configurations. The Nd:YVO4 crystal is pumped by a 808-nm laser diode and emit the light at wavelength of 671 nm through intracavity frequency doubling. In linear cavity, we demonstrate the Q-switched output performance by using three different front mirrors. Experimental results reveal that plano-plano cavity is the most suitable cavity design to obtain the highest output power. Based on the plano-plano cavity, we utilize three different pump mode size to explore the performance of laser output. At an incident pump power of 24.2 W, the output power can be up to 4.02 W with the pump mode size of 800 m. At the same time, we also explore the output performance by utilizing the V-shaped cavity. The maximum average output power is measured to be 5.3 W at a pump power of 24.2 W. This work enables us to optimize reliable active Q-switched lasers at 671 nm with efficient high average output power.
47
Kellner, Robert R. [Verfasser]. "STED microscopy with Q-switched microchip lasers / presented by Robert R. Kellner." 2007. http://d-nb.info/986021954/34.
Full text
48
Tang, Cheng-Yu, and 唐政猷. "Optimization and Wavelength Conversion of End-Pumped Q-Switched Solid-State Lasers." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/b2zmw6.
Full textAbstract:
博士國立交通大學
電子物理系所
104
The aim of this thesis is focused on developing compact reliable Q-switched Nd-doped crystal lasers based on linear cavity configuration, and these optimized near infrared lasers are subsequently applied for several nonlinear frequency conversions to effectively extend the spectrum from eye-safe to deep ultraviolet regimes. First of all, an energy adjustable passively Q-switched laser is demonstrated with a composite Nd:YAG/Cr4+:YAG crystal. We also exhibit a specially designed Nd:YAG/Cr4+:YAG miniature laser, which is constructed to manifestly show that the scale-up of the pulse energy without the negative effect due to the higher-order transverse modes can be practically realized by increasing the pump radius and setting the corresponding critical cavity length simultaneously. Then, we originally utilize a nearly hemispherical cavity to accomplish the energy scale-up for a high-repetition-rate nanosecond pulsed pumped Nd:YLF laser passively Q-switched by the Cr4+:YAG saturable absorber. Moreover, we employ the intracavity optical parametric oscillator to achieve a compact and efficient high-energy Nd:YLF eye-safe laser at 1552 nm. A novel system of 2D VCSEL arrays end-pumping module is utilized for realizing stable, high-quality, and high-energy Nd-doped PQS lasers. Finally, the optimized Q-switched Nd-doped crystal lasers are employed to produce green, ultraviolet, and deep ultraviolet radiations via extracavity harmonic generations. We first compare the output performance between the extracavity and intracavity second harmonic generations at 532 nm under a similar operated condition. We further perform extracavity third and fourth harmonic generations to effectually produce ultraviolet waves at 351 nm as well as deep ultraviolet radiation at 266 nm with output powers up to several watts. Efficient nonlinear frequency conversions not only enable us to produce the emission wavelengths from eye-safe to deep ultraviolet regions, but also confirm the usefulness of our cavity design for Q-switched lasers.
49
許展榕. "Supercontinuum Generation from Microstructured Fibers by a Q-Switched Mode-Locked Laser." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/35800535089038726158.
Full text
50
Lee, Yin-Wen, and 李穎玟. "Output Power Maximization of a Diode Pumped Passively Q-Switched Microchip Laser." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/86971500869292581560.
Full textAbstract:
碩士國立清華大學
電機工程學系
88
Optical characteristics of the laser gain medium, saturable absorber and reflectivity of the output coupler mirror determine the output performance of a passively Q-switched microchip laser. However, the conventional method of enhancing the peak power, in which the pulse width is narrowed by shortening the cavity length, has a complex chip fabrication process. Therefore, this thesis presents a novel means of increasing the peak power of a diode pumped passively Q-switched microchip laser with a fixed cavity configuration. The thermal focusing theory indicates that the laser mode size is enhanced by increasing the pump size and, simultaneously, increasing the peak power. Experimental results indicate that the proposed method enhances the pulse energy by 50% while simultaneously increasing the pump size by 50%, thereby increasing the output peak power under a fixed cavity configuration proportionally. Results in this study demonstrate that the proposed method optimizes the output peak power of a diode pumped passively Q-switched microchip laser without relying on a complex chip fabrication process. Furthermore, a compactly tunable visible laser is demonstrated by combing a monolithic PPLN and the passively Q-switched microchip laser, demonstrated herein.