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1
Stone, Robert John. "Optical studies of tunnelling in semiconductor quantum well systems." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339356.
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Xie, Feng. "Resonant optical nonlinearities in cascade and coupled quantum well structures." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3101.
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Vu, Hoan [Verfasser]. "Rolled-up plasmonic metamaterials coupled to quantum-well emitters / Hoan Vu." München : Verlag Dr. Hut, 2018. http://d-nb.info/1170473350/34.
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Vũ, Nguyên Mạnh Hoan [Verfasser]. "Rolled-up plasmonic metamaterials coupled to quantum-well emitters / Hoan Vu." München : Verlag Dr. Hut, 2018. http://d-nb.info/1170473350/34.
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Taylor, Thomas. "Exciton condensates and free carriers in microcavities and coupled quantum well structures." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/346833/.
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This thesis examines a series of effects associated with condensation in excitonic systems, and in particular in systems of microcavity exciton-polaritons and indirect excitons. A proposal is presented for a terahertz laser based on a microcavity system, in which a polariton condensate is formed, stimulating the terahertz transition from the 2p exciton state. An associated fundamental effect is predicted, in which the threshold to lasing is dependent on the statistics of the pump photons. The potential of hybrid Bose-Fermi systems for the study of coherent many body phenomena is demonstrated, by modelling the effects of interaction between an excitonic condensate and a two-dimensional electron gas. The fermionic subsystem of electrons is first considered, and it is shown that a phase transition to superconductivity may exist due to pairing mediated by virtual excitations of the condensate, analogous to the phonon mechanism in conventional superconductors. The system is modelled within BCS theory, and the gap equation is solved numerically to yield the critical temperature. The complementary effects of the electron gas on the bosonic condensate are also studied; the effective interaction between the constituents of the condensate may be strongly modified, affecting the superfluid properties of the condensate, and leading to the appearance of a roton minimum in the dispersion of elementary excitations. In fact, the dispersion may be modified to the extent that the roton gap closes, creating an instability in the system - it is shown that this instability may be manifested as a transition to a supersolid phase.
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Tomlinson, Andrew Michael. "Terahertz detection and electric field domains in multiple quantum wells." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302363.
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Bauer, Sven [Verfasser]. "High-Speed 1.55 µm Quantum Dot Lasers with Electronically Coupled Quantum Well - Dot Active Regions / Sven Bauer." Kassel : Universitätsbibliothek Kassel, 2019. http://d-nb.info/1201500753/34.
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Zhuang, Yuling. "Peripheral-coupled-waveguide multiple quantum well electro-absorption modulator for high efficiency, high spurious free dynamic range and high frequency RF fiber-optic link." Diss., Connected to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2005. http://wwwlib.umi.com/cr/ucsd/fullcit?p3181641.
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Thesis (Ph. D.)--University of California, San Diego, 2005.Title from first page of PDF file (viewed March 1, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Harrison, Paul Anthony. "Resonant tunnelling and luminescence in coupled quantum wells." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363933.
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Wilkes, Joe. "Hydrodynamics of indirect excitons in coupled quantum wells." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/43296/.
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This thesis comprises a theoretical study of the dynamics of indirect excitons in coupled quantum wells at low lattice temperatures. The results of numerical simulations of the exciton photoluminescence pattern are presented and compared to available experimental data. The in-plane transport of quantum well excitons created by laser excitation is modeled using a non-linear drift-diffusion equation. Combined with a model of exciton relaxation thermodynamics, a complete description of the evolution of the exciton density and temperature is built. The optical decay of indirect excitons is included in the modeling. This is used to make predictions of the spatial photoluminescence patterns which have been observed experimentally. The transport of dipole orientated excitons via externally applied electrostatic potentials is also studied. The drift-diffusion equation is adapted to include the inplane electric field. This is done for some specific forms of the potential landscapes such as a linear potential energy gradient and a propagating lattice. These correspond to some recent experiments for which results are available. The combined theoretical and experimental studies reveal a deeper insight into the transport properties of indirect excitons. Finally, the external ring structure in the indirect exciton emission pattern is studied. Its formation is modeled using a set of coupled transport equations for electrons, holes and indirect excitons. The Coulomb interactions between all three species are incorporated in the model. It is shown that these interactions lead to an instability in the external ring and are responsible for its fragmentation into a periodic array of islands which has been observed experimentally.
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Mouchliadis, Leonidas. "Transport and coherence properties of indirect excitions in coupled quantum wells." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54724/.
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This dissertation consists of a theoretical investigation into the transport and coherence properties of indirect excitons in coupled quantum wells (QWs) at helium temperatures. The motion of excitons along the quantum well plane is described through a quantum diffusion equation and the possibility of excitonic cloud formation is studied both due to the natural potential fluctuations and externally applied confining potentials. The photoluminescence (PL) of decaying excitons is used as a probe for their properties such as concentration, effective temperature and optical lifetime. The exciton thermalisation from an initial high energy to the lattice temperature is achieved within their lifetime due to a very effective coupling between the exciton states and a continuum of phonon states, a direct consequence of the relaxation of momentum conservation along the growth direction of a QW. Moreover, the natural spatial separation between electrons and holes prevents their recombination, resulting in long lifetimes. The dynamics of the system of excitons in optically-induced traps is also studied and the numerical solution of the quantum diffusion equation provides an insight into the extremely fast loading times of the trap with a highly degenerate exciton gas. The hierarchy of timescales in such a trap allows for the creation of a cold and dense gas confined within the trap, opening a new route towards the long sought Bose-Einstein Condensation (BEC) in solid state. Finally the issue of exciton spatial coherence is studied and an analytic expression for the coherence function, i.e., the measure of the coherence in a system, is derived. A direct comparison with large coherence lengths recently observed in systems of quantum well excitons and microcavity polaritons is attempted and interesting conclusions are drawn regarding the build up of spontaneous coherence in these systems.
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Cristofolini, Peter. "Optical control of polariton condensation and dipolaritons in coupled quantum wells." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/247219.
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Polaritons are lightweight bosonic quasiparticles that result from the strong coupling of light with an exciton transition inside a microcavity. A sufficiently dense cloud of polaritons condenses into a polariton condensate, a state of matter showing macroscopic coherence and superfluid properties, whose dynamics are influenced by the cycle of constant pumping and decay of polaritons. This thesis begins with an introduction on the particle and wave properties of the polariton condensate, followed by a theoretical description of two-dimensional Bose-Einstein condensation (BEC) and a section on simulation of polariton condensates. The optical setup and the microcavity sample are presented thereafter, including holographic laser shaping with a spatial light modulator (SLM), which allows exciting the microcavity with arbitrarily shaped pump geometries. Experimental results comprise optical control of polariton condensates, and dipolaritons. First, optical blueshift trapping and energy synchronisation (phase locking) of condensates are introduced. The transition from phase-locked condensates to an optically trapped condensate is investigated for a configuration of N pump spots arranged on a circle of varying diameter. Differences between these two condensate types are highlighted in the discussion section. Next, two parallel pump laser lines with small separation are investigated, which create a one-dimensional waveguide with strong uniform gain. Optically guided polaritons are investigated in this configuration with respect to coherence, flow speed, temperature and chemical potential. Observations hint that coherence arises below the condensation threshold simply from the chosen geometry of the system. The final chapter is dedicated to dipolaritons (polaritons with a static dipole moment) which form when polaritons strongly couple to indirect excitons in coupled quantum wells. In this system quantum tunnelling of electrons can be controlled with bias voltage. This allows tuning the dipolariton properties optically and electrically, with exciting prospects for future experiments. A conclusion and outlook section rounds off this work.
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Smallwood, Lois Elenid. "Thermalization, diffusion and photoluminescence of statistically-degenerate indirect excitons in coupled quantum wells." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/54566/.
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This thesis is a theoretical investigation into the properties of indirect excitons in coupled quantum wells at low lattice temperatures. The relaxational thermodynamics, optical decay and diffusion of the statistically-degenerate excitons are modelled theoretically and numerically. The excitons' thermalization from an initial energy, EJkB = 20-300 K, to the lattice temperature, Th 1 K, is investigated. The exciton optical creation and decay mechanisms are then included, as well as the change in the exciton effective temperature due to these mechanisms. While the optical creation heats the excitons, their optical decay produces an effect called 'recombination heating and cooling', and whether it produces a net cooling or a net heating of the exciton system depends on the exciton effective temperature, T. The system of excitons is also studied in two dimensions by using a quantum diffusion equation. The excitons are created by a laser pump with a cylindrically-symmetric spatial intensity profile. The created excitons move outwards from the excitation spot by drift and diffusion, and cool down while doing so. They become more optically- active as they cool, creating a ring of photoluminescence around the excitation spot. This ring was also seen in experiments of this kind. Theoretical results are fitted to experimental results, and the diffusion coefficient for exciton concentrations in the range of 0 < n2D < 2.5 x 1010cm-2 varies from 0.06 to 25cm2/s when Tb = 1.5 K, and the disorder amplitude in the sample is U 0.9 eV. Finally, a novel kind of laser trap used in experiments to spatially confine the excitons is modelled theoretically. While the experiments were carried out at Th = 1.5 K giving an occupation number of the ground state of 8, theoretical simulations show that for a lattice temperature of Tb = 0.4 K the occupation number of the ground state is 500. The trap is also modelled as a homogeneous trap, and simulations show that when Tb is decreased further the fraction of excitons in the ground state increases dramatically.
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Yang, Sen. "Spontaneous coherence, kinetics and pattern formation in cold exciton gases in GaAs/AlGaAs coupled quantum wells." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3359953.
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Thesis (Ph. D.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed August 20, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 79-84).
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Hammack, Aaron Tynes. "Studies of transport and thermalization of excitons and the development of techniques for in-situ manipulation of excitons in coupled quantum wells." Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p3403192.
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Beian, Mussie Thomas. "Spectral evidence for a condensate of dark excitons in a trap." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066671.
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Les excitons spatialement indirects, en tant que bosons composites, sont des candidats prometteurs pour l'exploration des systèmes corrélés à N-corps. Ils possèdent une dipôle électrique intrinsèque et une variété de spin 4 fois dégénérée, et devraient former un condensat de Bose-Einstein au-dessous de quelques Kelvins. De récents résultats théoriques montrent que cette condensation doit se produire au sein des états optiquement noirs. Néanmoins les interactions peuvent créer un couplage cohérent vers une population brillante, rendant ainsi accessible la détection du condensat par le biais de sa photoluminescence. Nos expériences portent sur un gaz froid d'excitons indirects dans un double puits quantique. Les excitons sont photo-générés par une excitation laser et confinés dans un piège électrostatique. Nous avons observé une réduction de la population d'excitons brillants pour un gaz de densité fixe à basses températures. Ceci contraste fortement avec le comportement attendu d'un gaz froid soumis à la statistique de Maxwell-Boltzmann. Ces résultats expérimentaux sont confirmés par un modèle phénoménologique montrant que la condensation dans les états noirs est compatible avec le noircissement anormal observé. Une réduction de la température pourrait en principe amplifier ces signatures, cependant dans le GaAs l'interaction exciton-phonon permettant le refroidissement est fortement réduite pour des températures inférieures au Kelvin. Nous avons donc développé une technique permettant le contrôle in-situ du confinement des excitons indirects sans échauffement du gaz, ouvrant ainsi la voie à l'exploration du refroidissement évaporatif des excitonsSpatially indirect excitons, being composite bosons, are attractive candidates to explore correlated many-body systems. They possess an inherent electric dipole and a four-fold spin manifold. Indirect excitons are expected to form a BEC below a few Kelvins. Recent theoretical results show this condensation must occur in optically dark states. Interactions, however, can lead to a coherent coupling to a bright population, rendering the condensate accessible through its PL. Here we report on a cold gas of indirect excitons in coupled quantum wells. indirect excitons are photo-generated through pulsed laser excitation. Indirect excitons are confined in an electrostatic traps. Thus, we are able to observe an anomaluos depletion of the bright state population for a fixed gas density at lower bath temperatures. This stands in stark contrast to the expected classical behavior of a cold gas of indirect excitons obeying Maxwell-Boltzmann statistics. The experimental results are confirmed by a phenomenological model showing that condensation into the dark state is compatible with the observed anomalous darkening. Reducing the gas temperature should reinforce these signatures. However, in GaAs exciton-phonon interaction is strongly reduced for sub-Kelvin temperatures. We have thus developed a technique to control the indirect excitons confinement in-situ. Our method does not increase the gas temperature and thus paves the way towards the exploration of evaporative cooling for indirect excitons
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Lynass, Mark Ronald. "Novel physics in two dimensional charge carrier structures : anisotropc magneto-transport at Landau-level crossings in aluminium arsenide quantum wells and coupled two dimensional electron and hole systems." Thesis, University of Bath, 2006. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428382.
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Venter, Johan H. "Dynamic range and sensitivity improvement of infrared detectors using BiCMOS technology." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/25267.
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The field of infrared (IR) detector technology has shown vast improvements in terms of speed and performance over the years. Specifically the dynamic range (DR) and sensitivity of detectors showed significant improvements. The most commonly used technique of implementing these IR detectors is the use of charge-coupled devices (CCD). Recent developments show that the newly investigated bipolar complementary metal-oxide semiconductor (BiCMOS) devices in the field of detector technology are capable of producing similar quality detectors at a fraction of the cost. Prototyping is usually performed on low-cost silicon wafers. The band gap energy of silicon is 1.17 eV, which is too large for an electron to be released when radiation is received in the IR band. This means that silicon is not a viable material for detection in the IR band. Germanium exhibits a band gap energy of 0.66 eV, which makes it a better material for IR detection. This research is aimed at improving DR and sensitivity in IR detectors. CCD technology has shown that it exhibits good DR and sensitivity in the IR band. CMOS technology exhibits a reduction in prototyping cost which, together with electronic design automation software, makes this an avenue for IR detector prototyping. The focus of this research is firstly on understanding the theory behind the functionality and performance of IR detectors. Secondly, associated with this, is determining whether the performance of IR detectors can be improved by using silicon germanium (SiGe) BiCMOS technology instead of the CCD technology most commonly used. The Simulation Program with Integrated Circuit Emphasis (SPICE) was used to realise the IR detector in software. Four detectors were designed and prototyped using the 0.35 µm SiGe BiCMOS technology from ams AG as part of the experimental verification of the formulated hypothesis. Two different pixel structures were used in the four detectors, which is the silicon-only p-i-n diodes commonly found in literature and diode-connected SiGe heterojunction bipolar transistors (HBTs). These two categories can be subdivided into two more categories, which are the single-pixel-single-amplifier detectors and the multiple-pixel-single-amplifier detector. These were needed to assess the noise performance of different topologies. Noise influences both the DR and sensitivity of the detector. The results show a unique shift of the detecting band typically seen for silicon detectors to the IR band, accomplished by using the doping feature of HBTs using germanium. The shift in detecting band is from a peak of 250 nm to 665 nm. The detector still accumulates radiation in the visible band, but a significant portion of the near-IR band is also detected. This can be attributed to the reduced band gap energy that silicon with doped germanium exhibits. This, however, is not the optimum structure for IR detection. Future work that can be done based on this work is that the pixel structure can be optimised to move the detecting band even more into the IR region, and not just partially.Dissertation (MEng)--University of Pretoria, 2013.
Electrical, Electronic and Computer Engineering
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Lamponi, Marco. "Lasers inp sur circuits silicium pour applications en telecommunications." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00769402.
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La photonique du silicium a connu un développent massif pendant les dix derniers années. Presque toutes les briques technologiques de base ont été réalisées et ont démontrées des performances remarquables. Cependant, le manque d'une source laser intégrée en silicium a conduit les chercheurs à développer de composants basés sur l'intégration entre le silicium et les matériaux III-V.Dans cette thèse je décris la conception, la fabrication et la caractérisation des lasers hybrides III-V sur silicium basés sur cette intégration. Je propose un coupleur adiabatique qui permet de transférer intégralement le mode optique du guide silicium au guide III-V. Le guide actif III-V au centre du composant fourni le gain optique et les coupleurs, des deux cotés, assurent le transfert de la lumière dans les guides silicium.Les lasers mono longueur d'onde sont des éléments fondamentaux des communications optiques. Je décris les différentes solutions permettant d'obtenir un laser mono-longueur d'onde hybride III-V sur silicium. Des lasers mono longueur d'onde ont été fabriqués et caractérisés. Ils démontrent un seuil de 21 mA, une puissance de sortie qui dépasse 10 mW et une accordabilité de 45 nm. Ces composants représentent la première démonstration d'un laser accordable hybride III-V sur silicium.
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Hsu, Wei-Cheng, and 徐偉程. "Studies of Surface Plasmon Coupled Quantum Well Infrared Photodetectors." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/u5xw76.
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博士國立交通大學
電子研究所
106
Surface plasmon has been widely used in different optoelectronic devices such as laser, solar cell and detectors in recent years. Due to its near field enhancement behavior, the surface plasmon generated through a two dimensional (2D) metal hole array can improve the coupling of the normal incident radiation for quantum well infrared photodetectors (QWIPs). In this thesis, we investigate the responsivity behaviors of surface plasmon coupled QWIPs with different devices structures parameters. In first part, we used a “non-uniform” structure we proposed before and compare the enhancement behaviors between etched grating coupling and surface plasmon coupling. All structures with surface plasmon have higher response compared to the cases with etched gratings. But at the same time, we found an unexpected bias dependence of response enhancement behavior, especially for the non-uniform structures. The non-uniform QWIPs with surface plasmon coupling showed an asymmetric enhancement behavior with respect to the bias directions. The non-uniform structure showed higher response enhancement when it had higher effective electric field near the collector while the uniform structure showed an equal enhancement in either bias direction. The change of the photoelectron escape probability due to the narrow coupling bandwidth of the surface plasmon is attributed to this bias dependence. We used an equation including the parameters such as effective electric field, barrier energy, mean value and variance of the excited state energy to explain the differences of escape probabilities of different structures (non-uniform and uniform QWIPs) and different couplings (etched grating and surface plasmon). We got reasonable fitting results for all structures in both positive and negative bias regions. With surface plasmon coupling, the highest detectivity 5.36E10 cmHz0.5/W was achieved for the reverse non-uniform structure at 77K. In second part, we studied the wavelength tuning behavior of surface plasmon coupled QWIPs. The peak wavelength of the surface plasmon is related to the array period and the dielectric constants of the materials. The peak wavelength red shifted as we reduced the top contact layer due to a decrement of low refractive index material in the whole structure. By choosing the longest wavelength at the long-wavelength tail of the quantum well absorption, the responsivity and detectivity can be kept within a reasonable range as we increase the contact thickness. The peak wavelength changes from 8.53 μm to 8.28μm as the top contact layer increased from 50nm to 1000 nm in our experiments. Meanwhile, the responsivity only decayed around 36 % (from 0.255 A/W to 0.162 A/W), which is much smaller compared to the previous result in the similar contact thickness range, thanks to a proper choice of the array period. We also simulated the absorption spectra based on the method of rigorous coupled-wave analysis (RCWA). Similar trend was found for the wavelength tuning behavior when we only changed the top contact thickness in the simulation structure. By further considering the quantum well absorption and the different lithography condition that result in bigger hole diameter, reasonable simulation results for peak response could be obtained compared to our experiment results. In the third part, we investigate the enhancement difference of quantum efficiency (QE) between etched grating and surface plasmon devices as we increased the well doping of QWIPs. Compared to the previous discussion for QWIPs that the detectivities was nearly independent of well doping from 4.7E16 cm-3 to 1.5E18 cm-3, the surface plasmon coupled QWIPs showed a similar appearance as we changed the well doping from 1E17 cm-3 to 1E18 cm-3. However, compared to the etched grating samples, the QE enhancement reduced in negative bias compared to positive bias as we increased the well doping for surface plasmon samples. The enhancement difference was bigger for surface plasmon samples than etched grating samples. Due to a narrowing distribution of photoelectrons in the excited of quantum well, the surface plasmon samples were more sensitive to the change of electric field (change of well doping). In addition, the potential spike between the AlGaAs/GaAs interface would lower the escape probability in negative bias. Therefore, the increment differences between positive and negative would become larger for surface plasmon samples than etched grating samples. Though the enhancement of surface plasmon samples was different for these dopings, the detectivities differences were kept within a factor of three. All the samples with detectivity of 1×1011 cmHz0.5/W were achieved at 77K. The highest detectivity 2.92E11 cmHz0.5/W was achieved with 3.3E17 cm-3 well doping at +1V.
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WU, ZHAO-NENG, and 吳昭能. "Second-order nonlinear optical susceptibility of coupled quantum well." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/59384186042057549041.
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王于肇. "Photonic Crystal Multichanneled Filters Containing Coupled and Photonic Quantum-well Defects." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/01514437756301890028.
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碩士國立臺灣師範大學
光電科技研究所
99
In the last two decades, the periodically arranged dielectric structures known as photonic crystals (PCs) have found their potential applications in various optoelectronic devices. The devices make use of the features of photonic band gaps (PBGs) originating from the periodic nature of PCs. When the periodicity is broken by introducing a defect into the PCs, a defect mode will appear inside the photonic bandgap and this is analogous to the electronic impurity state of semiconductors. In this thesis, we consider different defective photonic crystals that can work as a multichanneled filter. Three main topics will be involved. The first structure called the impurity band-based photonic quantum well (IBBPQW) is (AB)m(ABAC)nABA(BA)m , where AB denotes the unit cell, C denotes the defect, and the number of defects is n. The IBBPQW can make more effective use of the localization properties of the electromagnetic (EM) field. The IBBPQW structure can be constructed with great freedom since the impurity band is naturally located inside the gap and the bandwidth of the impurity band can be tuned by changing the separation between the defects and the size or refractive indexes of the defects. In the second structure, we shall consider the photonic quantum-well as a defect in a host PC, i.e., (AB)m(CD)n(AB)m . If the photonic pass band of the photonic crystal(CD)n is just located into the photonic band gap of the photonic crystal (AB)m, quantized confined photonic states will appear owing to the photonic confinement effects. It is found that the number of the confined states can be tuned by adjusting the number of period of the well region, leading to the phenomena of multiple channeled filtering. In the third part, we continue to examine the other condition that the photonic pass band of the photonic crystal (CD)n is partially located into the photonic band gap of the photonic crystal (AB)m. In this case, the number of the confined states can be again tuned by adjusting the number of period of the well region, leading to the phenomena of multiple channeled filtering. However, the number of channels is not the same as the second case. A different design rule will be provided. The whole theoretical analysis in this thesis is based on the transfer matrix method which will be given in Chapter 2. Chapter 1 is to give a brief introduction of PCs. Three main topics are given in Chapters 3, 4 and 5, respectively. The conclusion is in Chapter 6.
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Liu, Juin-Ming, and 呂俊明. "Design of Polarization-Independent Electro-absorption Modulator Using Strain Coupled Quantum Well." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/45030865192887483766.
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碩士國立清華大學
電機工程學系
85
A new alternative-strain compensated InP/InGaAs/InP/InAsP/InP polarization independent anti-symmetric coupled-quantum-well (CQW) structure with both blue and red quantum-confined Stark shift for the first heavy-hole-to-electron (or the first light- hole-to-electron) excitonic transition is studied theoretically in this thesis. In the anti-symmetric coupled-quantum-well (CQW), an anti-symmetric-like pair of potential profile between the shallow-deep conduction band profile and the deep-shallow valence band profile is formed. The subband eigenenergies and the associated envelope wave functions in the CQW structures with or without applied electric field are calculated by the transfer matrix method. The effects of the strain on the pseudomorphic layers has been taken into account. The influence of various anti-symmetric CQW structure parameters such as the total well width, the individual well width, the central barrier thickness and the composition of the strained layer on transition energy, QCSE, the envelope wavefunction overlap, and on/off ratio are studied systematically. In addition, the tradeoff between the polarization-independent requirement and the strength of the blue Stark Effect has been discussed. Results indicated that: First, the use of the tensile-strained well is to help to meet the polarization-insensitive condition while that of the remaining compressive-strained well and middle barrier is to help tuning the transition energy to the desired wavelength and simultaneously achieving larger blue shift and wavefunction overlap. Second, in either blue- or red- shift applications, the alternative-strain compensated anti-symmetric polarization-independent CQW structure could gather around superior properties to design the polarization independent electroabsorption modulator because the novel structure could give large enhancement of both blue and red Stark Effect. The design of the novel polarization-independent electroabsorption modulator operated at 1.3mm utilizing either blue or red Stark Effects in the alternative-strain compensated polarization-independent anti-symmetric couple quantum well (CQW) is proposed and studied theoretically in this thesis. The InP/In0.379Ga0.621As(40A)/InP(6A)/InAs0.4P0.6(40A)/InP alternative-strain compensated polarization-independent anti- symmetric CQW is adopted. A value of as high as 5.7 can be achieved by either blue or red Stark Effects shift of the anti- symmetric CQW in the electric field range of 0 to 125kV/cm for blue-shift and 0 to -250kV/cm for red-shift applications. Also, we use In0.409Ga0.591As(52A)/InP operated at 1.3 mm to design the modulator for comparison. Our result shows that in virtue of our novel strain compensated polarization independent anti- symmetric CQW structure, the performance of our novel device, such as switching energy, drive voltage, and the net strain in the device, could be dramatically improved in comparison with the conventional InGaAs/InP SQW modulator.
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Chen, Yimin, and 陳益民. "The Electric-field-dependent Optical Absorption of the Antisymmetric Coupled Quantum Well." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/21356071576319077903.
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Tien, Yao Cheng, and 田曜丞. "A single photon emitter implemented by electrostatically-gate asymmetric coupled quantum well." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/59055261583259659971.
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碩士國立清華大學
光電工程研究所
104
We present the modeling of dipolar excitons in AlGaAs based, asymmetric coupled quantum wells with a vertical electric field induced two-dimensional electrostatic trap. We theoretically show that when the trap size and depth are carefully engineered, it is possible for the system to enter an exciton blockade regime in which single photon emissions can be obtained. Due to the unique properties such as the trap geometry and position can be precisely defined by photolithography, the proposed single photon emitter may find new applications in quantum information processing.
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Wang, Chih-Lun, and 王志倫. "The Optical and Electrical Characteristics of InGaN Multiple Coupled Quantum Well Blue LEDs." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/00039714675870020485.
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碩士長庚大學
電子工程研究所
95
Abstract In this study, we grow four InGaN/GaN multiple quantum well (MQW) LED structures by MOVPE on c-plane sapphire substrates. For investigating the coupled structure influence, we insert a short InxGa1-xN barrier in the center of the quantum well named as multiple coupled quantum well (MCQW). First the temperature dependences of photoluminescence ware performed to verify the sample’s emission peak position and the other characteristics. The results showed that with increasing indium composition in the InxGa1-xN barrier of the MCQW, the emission peak position was redshift and exhibited different behaviors of emission mechanisms in these samples. We also used X-ray diffraction (XRD) and reciprocal space map (RSM) to confirm the indium composition of the short InxGa1-xN barrier of the MCQW. From current dependences of electroluminescence (EL) measurements, we found out more about the emission mechanism of the samples. Finally, of the electrical-optical characteristics were study by the current-voltage measurement (I-V) and the light output power-current measurement (L-I).
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Wu, Sung-Lin, and 吳松霖. "Photoluminescence Study of Zn0.48Cd0.52Se/Zn0.24Cd0.18Mg0.58Se Asymmetric Coupled Quantum Well Structure Grown by MBE." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/a3zzcb.
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碩士明志科技大學
電子工程系碩士班
102
Photoluminescence (PL) was used to characterize the optical transitions in a ZnCdSe/ZnCdMgSe asymmetric coupled quantum well (ACQW) structure grown on InP substrate by molecular beam epitaxy. The PL spectra revealed the situation of the optical transition in the ACQW structures. Using Gaussian line shape to fit transition energies depends on temperatures. Then use Varshni and Bose-Einstein relation consistent transition energy depends on temperature, the parameters obtained value analysis of the optical characteristic of the transition energy of ZnCdSe/ZnCdMgSe ACQW depends on temperature and determine the reliability of the experimental data. The PL spectra for the ACQW sample in the temperature range from 10 to 300 K. The PL peak monotonically shifts toward lower energy and broadens with increasing temperature in the same temperature range above. Thus, using Varshni and Bose-Einstein formula to analyze the optical signal that fit the theory of temperature dependent characteristic from the temperature range. The parameter of boarding function to assess, analyze and discuss. Finally, study of ZnCdSe/ZnCdMgSe ACQW structure of the integrated PL intensity as a function of laser excitation power density. The relation between the integrated PL intensity and the excitation density where γ is a fitting parameter. The fitted values γ that at the measured temperature range the luminescence is dominated by exciton recombination. The results demonstrate the potential of PL techniques for the contactless and nondestructive characterization of the wide band gap II-VI QW structures for mid-IR intersubband device applications.
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Heller, Richard Dean. "Short-wavelength InAl(x)Ga(1-x)P quantum well lasers and InP quantum dot coupled to strained InAl(x)Ga(1-x)P quantum well lasers grown by MOCVD." Thesis, 2003. http://hdl.handle.net/2152/640.
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Heller, Richard Dean Dupuis Russell. "Short-wavelength InAl(x)Ga(1-x)P quantum well lasers and InP quantum dot coupled to strained InAl(x)Ga(1-x)P quantum well lasers grown by MOCVD." 2003. http://wwwlib.umi.com/cr/utexas/fullcit?p.
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Ko, Yu-Chen, and 葛于臣. "Control of the Magnetic Polaron Formation Mechanism by Different Carrier Lifetime in ZnMnTe Quantum Dots Coupled with ZnCdSe Quantum Well." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/7y9kch.
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碩士國立交通大學
電子物理系所
105
In this thesis, type II ZnMnTe quantum dots coupled with type I ZnCdSe quantum well were grown by molecular beam epitaxy (MBE). By controlling the ZnSe spacer layer of 2 and 5 nm, we can adjust the carrier lifetime to study the effect on the magnetic polaron formation. By using photoluminescence (PL) spectroscopy with different laser wavelength and time-resolved PL spectrum, we could identify the change of carrier recombination route in different spacer layer. A red shift of peak energy was observed in the time-dependent PL spectrum, because of the change of carrier recombination route and the magnetic polaron formation. The carrier life time was extended in the sample of 0.1% Mn concentration ZnMnTe quantum dots coupled with ZnCdSe quantum well with 5nm ZnSe spacer layer, the energy of magnetic polaron formation was also enhanced by 4 to 5 times.
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Harff, Nathan E. "Electron transport in coupled double quantum wells and wires." Thesis, 1997. http://hdl.handle.net/1957/34430.
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李恭儀. "Multiple tunneling and chaos in asymmetric coupled quantum wells." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/09669899326186103253.
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HUANG, YI-MIN, and 黃益民. "The design of tunable coupled quantum wells far-infrared detectors." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/41460239391614177704.
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Jao, Chung-Chieh, and 饒中傑. "Studies of optical absorption and resonant tunneling in coupled quantum wells." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/90481188790616372679.
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碩士國立交通大學
電子物理系
88
There are two parts in the thesis. In the first part, we investigate the optical absorption in symmetric and asymmetric coupled quantum wells that consist of two wells and a thinner barrier. Comparing with single quantum well, the coupled quantum well has a larger Stark effect. It also has more freedom to adjust the widths of wells and barrier to acquire a desirable optical property. In the study, we calculate the absorption coefficient of various coupled quantum wells with two eigenstates. By using beam propagation method (BPM), we simultaneously solved time dependent Schrödinger equation and Poisson equation to acquire of wave functions and eigenenergies. By invoking of density matrixes, we calculated the linear susceptibility and the linear absorption coefficient of coupled quantum-well systems. In the second part, we study the resonant tunneling effect of coupled quantum wells in the external electric. We explored electron dynamical evolution relating to the variation of the external electric field strength, barrier thickness, and electrons sheet density. Finally, we apply longitudinal magnetic field to the coupled quantum wells to study electron resonant effects. In a resonant condition, the tunneling time decreases with the increasing of magnetic field.
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Cai, Qing Bin, and 蔡清斌. "Chaotic behavior of hole mixing tunneling in asymmetric coupled quantum wells." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/86495615119265573067.
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WANG, JUN-FU, and 王俊富. "Second-order nolinear optical susceptibilities of compositionally asymmetric coupled quantum wells." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/21033261869570018764.
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Sung, Li-Wei, and 宋立偉. "Study of 1.55 μm asymmetric couple quantum well active layer laser-modulator OEIC." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/71295556112505772690.
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碩士國立臺灣大學
電機工程學研究所
87
In this study, we realize 1.55μm DFB laser - modulator optoelectronic integration circuits by using identical active layer (IAL) approach which applies the same active layer in laser and modulator. To solve the intrinsic problem in identical active layer approach that the laser gain spectrum is too close to the modulator absorption, a novel asymmetric couple quantum well structure was designed to enlarge the separation between the gain and absorption spectrum theoretically. Then two epitaxial samples with conventional QWs and asymmetric couple QWs were grown by gas source MBE and processed to be broad area lasers and PIN photo diodes. From the measurement results of those devices, the theoretical calculation is proven. Finally, 1.55μm DFB laser - modulator optoelectronic integration circuits with 13dB Extinction ratio are demonstrated.
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CHEN, YU-WEI, and 陳與偉. "Growth and characteristics of photoluminescence of coupled CdSe quantum dots/ZnSe/ZnCdMnSe quantum wells grown by molecular beam epitaxy." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/98258501799475680141.
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碩士中原大學
物理研究所
100
The coupled structures of self-assembled CdSe quantum dots (QDs) separated by a thin ZnSe barrier from a ZnCdMnSe quantum wells (QWs) were studied. Atomic force microscopy (AFM) and photoluminescence (PL) were employed to investigate the surface morphology and the optical properties respectively. A PL peak originated from the CdSe QDs and two PL peaks originated from the phase-separated ZnCdMnSe QWs were observed. Furthermore, we investigated the effect of thickness of ZnSe spacer on the coupling of the CdSe QDs and the ZnCdMnSe QWs. As the thickness of ZnSe spacer layer was less than 20 nm, the PL intensity originated from the QWs decreased with the thickness of spacer layer decreased. The results consist with the tunneling effect of carriers in the coupled structures.
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Wu, Tsu-Hsiu, and 吳祖修. "All-optical wavelength converter by field-driven quantum well device integrated with vertical waveguide directional coupler." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/52762159241264617059.
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博士國立中山大學
光電工程學系研究所
99
In present dissertation, field-driven quantum well (QW) device is proposed to obtain high-speed and high-efficiency all-optical wavelength converter (AOWC). A new type QW material, InGaAsP/InGaAlAs, is employed to improve not only quantum confined Stark effect, but also carrier life time during high electric field excitation. The bandwidth as well as efficiency can be enhanced. Thus, the slow gain recovery mechanism (~100ps) from conventional semiconductor optical amplifier (SOA)-based AOWC can be overcome. The dispersion- and efficient- limited fiber-based AOWC (~10ps) can also be avoided. -3dB frequency bandwidth exceeding 40GHz for both electrical-to-optical and photocurrent response has been observed from InGaAsP/InGaAlAs waveguide of AOWC, leading to above 40GHz bandwidth in optical-to-optical response. A 40 Gb/s measurement setup is finally used for testing eye-diagram and bit-error-ratio in order to verify the data transmission of AOWC. Low power penalty with 0.5 dB comparing with back-to-back system performance is measured, suggesting InGaAsP /InGaAlAs waveguide is applicable to all-optical processing. By exciting short optical pump pulse in such waveguide, as short as 6.4ps probe pulse is observed, breaking through 10ps order in conventional type of QW and thus indicating the plausibility of performing 100Gb/s all optical processing.
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Huang, Yi Min, and 黃益民. "Optical and electronic properties of coupled quantum wells and their application to electro-optical devices." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/72486735285086283422.
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