Tesis sobre el tema "Quantum stark effect"
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Panda, Sudhira. "Quantum confined stark effect and optical properties in quantum wells". Thesis, Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19324303.
Texto completoGibb, Kevin. "The quantum confined Stark effect and Wannier Stark ladders in InxGa1-xAs quantum wells and superlattices". Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7704.
Texto completoHuang, Xuan. "Monolithically integrated quantum confined stark effect tuned semiconductor lasers". Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368167.
Texto completoSala, Matthieu. "Quantum dynamics and laser control for photochemistry". Thesis, Dijon, 2015. http://www.theses.fr/2015DIJOS039.
Texto completoThe central subject of this thesis is the theoretical description of ultrafast dynamical processes in molecular systems of chemical interest and of their control by laser pulses. We first use electronic structure calculations to study the photochemistry of aniline. A umber of previously unknown features of the potential energy surfaces of the low-lying elec-tronic states are reported, and analyzed in relation with the experimental results available. We use quantum dynamics simulations, based on a model Hamiltonian including the four lowest excited electronic states and sixteen vibrational modes, to investigate the photochem-istry of pyrazine. We show that the dark Au(nπ∗) state plays an important role in the ultrafast dynamics of the molecule after photoexcitation. The laser control of the excited state dynamics of pyrazine is studied using a simplified two-state four-mode model Hamiltonian. We propose a control mechanism to enhance the lifetime of the bright B2u(ππ∗) state using the Stark effect induced by a strong non-resonant laser pulse. We finally focus on the laser control of the tunneling dynamics of the NHD2 molecule, using accurate full-dimensional potential energy and dipole moment surfaces. We use simple effective Hamiltonians to explore the effect of the laser parameters on the dynamics and design suitable laser fields to achieve the control. These laser fields are then used in MCTDH quantum dynamics simulations. Both enhancement and suppression of tunneling are achieved in our model
Yeo, Hwee Tiong. "High responsivity tunable step quantum well infrared photodetector". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FYeo.pdf.
Texto completoBadada, Bekele H. "Probing Electronic Band Structure and Quantum Confined States in Single Semiconductor Nanowire Devices". University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470043382.
Texto completoMalins, David B. "Ultrafast dynamics in InAs quantum dot and GaInNAs quantum well semiconductor heterostructures". Thesis, University of St Andrews, 2008. http://hdl.handle.net/10023/404.
Texto completoAganoglu, Ruzin. "Non-linear Optical Properties Of Two Dimensional Quantum Well Structures". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/3/12607089/index.pdf.
Texto completoRamanathan, Sivakumar. "Optical Characterization of Electrochemically Self-Assembled Compound Semiconductor Nanowires". VCU Scholars Compass, 2006. http://scholarscompass.vcu.edu/etd/1436.
Texto completoDonon, Jeremy. "Caractérisation de paires d’ions par spectroscopies IR, UV et rayons X, interprétées par calculs de chimie quantique". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS106.
Texto completoIon pairs are ubiquitous in nature, from sea water, aerosols, to living organisms. They influence the properties of concentrated ion solutions, and thus play a crucial role in various chemical reactions and biological processes. However, the characterization of ion pairs faces some difficulties: on one hand, several types of pairs coexist, and on the other hand, they are transient species in solution. In this context, this work presents several studies carried out according to three main research studies, backed by an original approach in the gas phase, and then in solution. Firstly, the effects of the electric field produced by the ion pair on the UV spectroscopy of a chromophore in gas phase (Stark effects) are studied. The ion groups can produce an electric field high enough to induce significant electronic Stark effects on a nearby UV chromophore. This study is conducted on model systems (C₆H₅-(CH₂)n-COO⁻,M⁺) with M = Li, Na, K, Rb, Cs and n = 1-3, allowing to vary the electric field experienced by the UV chromophore. These different systems are studied in the gas phase by UV spectroscopy combined with quantum chemistry calculations, as well as by conformation selective IR spectroscopy. Based on the analysis of the electronic Stark effects, precise conformational assignments can be proposed for electronic transitions separated by a few cm-1, without resorting to IR spectroscopy, or frequency calculations. The next study is focused mainly on understanding the environmental effects on ion pairs by microsolvation experiments in gas phase. The pair of sodium acetate ions [CH₃-COO⁻,Na⁺] is studied for the first time in a trimer complex with p-xylene by IR spectroscopy. Microhydration experiments are then carried out on charged ion pairs ([CH₃-COO⁻,M²⁺]; M = Ca, Ba), highlighting two different behaviours depending on the nature of the cation. The final research is to detect and identify the structures formed by the ions in electrolytic solutions by IR and RX spectroscopy. The first experiment is carried out on electrolytic solutions ([CH₃-COO⁻,M⁺]; M = Li, Na and K) by TF-IR spectroscopy by varying the ion concentration. A theoretical study is then carried out in order to propose a theoretical spectrum for each type of pair, and to confront them with experimental spectra in solution. The approach is based on the calculation of the IR signature of pairs ([CH₃-COO⁻,M⁺]; M = Li, Na, K, Rb and Cs) and free anion in solution, where the first solvation layer were described at the quantum level, followed by a solvent continuum. For each type of pair, spectroscopic families, consistent with the experimental data, are identified. This original approach paves way to the identification of supramolecular structures in electrolytic solutions. Finally, the first FZRET experiment in liquid micro-jet is carried out on a potassium acetate solution, providing access to a measurement of the distance distribution between cations and paired anions.In these studies, different methods are used ranging from experiment to theory, from the gas phase to solution. This work illustrates the need to combine several methods in order to obtain additional data and allow a better characterization of the supramolecular organisation of ions and their environment
Saab, Mohamad Yehia. "Photochimie organique guidée par pulses laser : Applications : Benzopyrane et Pyrazine". Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20014/document.
Texto completoThe ring-opening photoisomerization of benzopyran, which occurs via a photochemical route involving a conical intersection,has been studied with quantum dynamics calculations using the multi-configuration time-dependent Hartree method (MCTDH). We introduce a mechanistic strategy to control the conversion of benzopyran to merocyanine with laser pulses. We use asix-dimensional model developed in a previous work for the potential energy surfaces (PES) based on an extension of thevibronic-coupling Hamiltonian model (diabatization method by ansatz), which depends on the most active degrees of freedom. The main objective of these quantum dynamics simulations is to provide a set of strategies that could help experimentalists tocontrol the photoreactivity vs. photostability ratio (selectivity). In this work we present:(i) a pump-dump technique used tocontrol the photostability, (ii) a two-step strategy to enhance the reactivity of the system: first, a pure vibrational excitation inthe electronic ground state that prepares the system and, second, an ultraviolet excitation that brings the system to the firstadiabatic electronic state; (iii) finally the effect of a non-resonant pulse (Stark effect) on the dynamics
Haas, Helge. "Effet Stark quantique dans les puits de CdTe/CdZnTe et développement d'un dispositif photoréfractif". Université Joseph Fourier (Grenoble ; 1971-2015), 1995. http://www.theses.fr/1995GRE10146.
Texto completoRakotonanahary, Georges. "Spectroscopie des transitions excitoniques dans des puits quantiques GaN/AlGaN". Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2011. http://tel.archives-ouvertes.fr/tel-00662445.
Texto completoMohamed, Sherif. "Carrier Dynamics in InGaN/GaN Semipolar and Nonpolar Quantum Wells". Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177906.
Texto completoChaisakul, Papichaya. "Ge/SiGe quantum well devices for light modulation, detection, and emission". Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00764154.
Texto completoSchmidt, Johannes [Verfasser], Manfred [Gutachter] Helm, Manfred [Akademischer Betreuer] Helm y Karl [Gutachter] Unterrainer. "THz pump-probe spectroscopy of the intersubband AC-Stark effect in a GaAs quantum well / Johannes Schmidt ; Gutachter: Manfred Helm, Karl Unterrainer ; Betreuer: Manfred Helm". Dresden : Technische Universität Dresden, 2020. http://d-nb.info/1227196849/34.
Texto completoRau, Björn. "Spontane und stimulierte Emission von (Al, In, Ga)N-Halbleitern". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2003. http://dx.doi.org/10.18452/14870.
Texto completoIn this thesis, the optical properties of molecular beam epitaxy grown hexagonal group-III nitride heterostructures are studied. The photoluminescence (PL) characteristics of InGaN/GaN and GaN/AlGAN multiple quantum well structures are investigated by time-integrated and time-resolved measurements. The analyzed specimens differ in the width of the quantum wells and barriers (InGaN) and in the crystallographic orientation (AlGaN), respectively. As a result of the large characteristic electrostatic fields, conventional [0001]-oriented heterostructures show a reduced transistion energy and longer lifetimes with increasing well width and higher Indium content in the wells. The observed impact of the Quantum Confined Stark Effect (QCSE) on these quantities is quantitatively shown in model calculations. In this work, a first extensive optical characterization of a novel [1-100]-oriented GaN heterostructure grown on Gamma-LiAlO2 is presented. For comparison, an identically designed [0001]-oriented structure on SiC is discussed. The (1-100)-grown specimen is free of electrostatic fields along the growth direction and shows a significant different behavior than conventional [0001]-oriented nitrides with internal fields of several MV/cm. The existing flat band conditions are confirmed by the spectral position of the PL at low excitation densities. Due to the non-existing QCSE at this specimen an significantly reduced lifetime is observed. A strong polarization of the PL is observed for the [1-100]-oriented sample, following the selection rules for hexagonal GaN. The small deviation of the degree of polarization from unity, which is expected in bulk GaN, is attributed to the quantum confinement in the heterostructures. One main topic of this thesis is the analysis of the recombination mechanisms of the specimens depending on the induced carrier density. The carrier density is varied from very low upto densities above the mott density. A screening of the electrostatic fields is observed with increasing carrier density. It is shown, that an InGaN/GaN heterostructure with a well width of 3.1 nm not only is influenced by internal piezoelectric fields but also the localization of excitons at stoichiometric inhomogenities in the quantum well is playing an important role for the recombination dynamics of the structure. This can be seen in the dependence of the decay process on the starting conditions. No general correlation is existing between lifetime and carrier density. Time-resolved PL measurements on InGaN/GaN heterostructures show a reduced lifetime due to an increased overlap of the electron and hole wave functions as a result of the increased screening at increasing carrier densities. During the recombination process the screening decreases again and the lifetime is changed with time. Simultaneously the transistion energy of the PL maximum is reduced by the less screened QCSE. A distinct dependence of the time-integrated PL spectra on the excitation density was also found. While there are no compensation effects expected at the (1-100) structure, which is free of electrostatic fields, the results for the conventional specimens point to an effect which influences the carrier density essentially. The dependence of the PL intensity on the carrier density points to an additional process, which comes into play at a special excitation density. This process reduces the carrier density but is invisible in the PL spectra. As an explanation we assume, that light of stimulated emission is absorbed either in the substrate or in the buffer layer. The transistion energy of the InGaN structures increases with increasing excitation density and reaches a saturation energy at a density of 10e5 W/cm2. Although this density is larger than the mott density, the transistion energy is not equivalent with a transition energy at flat band conditions. The origin of the observed effect is assumed to be the rival process, mentioned above, which comes into play at high carrier densities. For the GaN/AlGaN heterostructures no spectral shift of the PL was observed within the variation of excitation density. For the very first time, the stimulated emission of an [1-100]-oriented GaN structure was analyzed. A maximum netto gain of 50 1/cm was observed. From calculations of the mode propagation, a material gain of 1.1x10e4 1/cm is derived for GaN(1-100). Additionally from the results follows that the recombination of an electron-hole-plasma is the mechanism of the stimulated emission. This is in accordance with most of the published observations for [0001]-oriented GaN heterostructures. A direct comparison of both, the [1-100]-oriented specimen and the GaN/AlGaN(0001) structure, which was investigated parallel, was not possible. The reason for that is the strong absorption of the SiC substrate of the latter mentioned structure. It is generally shown, that [1-100]-oriented GaN heterostructures offers good starting conditions to realize laser diodes. The wave guiding was simulated for all of the used specimens. At structures grown on SiC the propagating modes are mainly guided in the substrate due to the larger refractive index of SiC with respect to GaN. The overlap of the amplified mode and the active layer is very small. No optical gain is expected for these structures. The [1-100]-oriented GaN/AlGaN structure shows a significantly improved wave guiding, due to the small refractive index of LiAlO2 in comparison with GaN. A correlation between the experimentally observed optical gain and the material gain is formed and the results are compared with the literature. A suggestion for an optimized wave guiding in all investigated specimens is given.
Baaboura, Jassem. "Effets de confinement quantique dans les matériaux de faible dimension dévoilés par des spectroscopies électroniques corrélées dans le temps". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP025.
Texto completoA profound understanding of interactions within luminescent materials under excitation is imperative for advancing optoelectronic devices. Materials with small dimensions exhibit unique optoelectronic properties resulting from quantum effects and spatial confinement.Our approach to analyzing the optoelectronic properties of nanomaterials is marked by a versatile methodology, employing various techniques integrated into the scanning transmission electron microscope (STEM). Utilizing an accelerated electron source at 60 keV, our study successfully overcame diffraction limitations. The STEM microscope, with nanometric resolution capabilities in measuring energy absorption through transmitted electron energy loss spectroscopy (EELS), formed the central aspect of our exploration. Enhanced by an integrated spectroscopic system into the microscope, we performed an in-depth analysis of the luminescence spectrum (cathodoluminescence) of nanostructures.The integration of these techniques facilitates the exploration of optoelectronic effects induced by excitons in low-dimensional materials, particularly in monolayer TMD-based heterostructures (WS2 et MoSe2) that were carefully prepared in a cleanroom. Luminescence mappings revealed correlations between the emission intensity of exciton XA and the trion, depending on the spatial displacements of the probe across the sample surface. These observations enabled deductions about the dependence of trion or exciton generation on the deformations of the layers within the heterostructure.Excitation by an electron source induces multiple electronic transitions, presenting a challenge compared to optical excitation. To tackle this challenge, the STEM team at LPS developed an experimental technique, the cathodoluminescence excitation spectroscopy (CLE), to identify the electron responsible for the emission of each photon. This identification, coupled with the magnetic spectrometer providing information on the energy absorbed by the sample, facilitates identifying the type of excitation leading to photon emission. The identification of the electron responsible for photon emission was achieved through temporal coincidence, utilizing a photomultiplier and a temporally resolved electron detector, Timepix3.A thorough investigation of the Timepix3 detector during this thesis unveiled the underlying mechanisms, spanning from the initial impact of the electron on the detector surface to its subsequent detection within the readout layer. This study, incorporating various experimental approaches, significantly contributed to the precise characterization of the detector, ultimately optimizing its temporal resolution.The temporal coincidence technique was applied to other low-dimensional materials, such as AlN nanowires with GaN/AlN quantum wells. This approach provided insights into the lifetime of excitations, uncovering a close dependence on the screening of the electric field within these nanowires. Simulations and experimental results demonstrated notable variations based on the current and spatial excitation position within the nanowire. While these dependencies are distinct, they are closely interlinked, influencing the migration of charges from barriers to wells and thus exerting a significant impact on the lifetime and emission energy of excitons.Finally, an energy-dependent study of electrons coinciding with photons unveiled the emission efficiency for each energy absorption, highlighting specific de-excitation processes leading to exciton generation, resulting in photon emission.These results not only enhance our comprehension of low-dimensional materials but also forge new pathways for the development of optoelectronic devices, particularly LEDs
Bahlak, Samia. "Contribution à l'étude d'un modulateur acousto-optique à puits quantiques". Valenciennes, 1997. https://ged.uphf.fr/nuxeo/site/esupversions/a93e0d34-1079-4e51-b081-345993233dd1.
Texto completoRamanathan, Swati. "Spin and Tunneling Effects in Coupled Quantum Dots". Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1324486727.
Texto completoAltevogt, Torsten. "Der optische Start-Effekt mit quantisiertemStrahlungsfeld". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2000. http://dx.doi.org/10.18452/14465.
Texto completoThe theoretical description of spectroscopic experiments usu ally relies on a semiclassical approach where the matter system is described in terms of quantum mechanics while the radiation field is treated classically. This approach does n ot work well for systems with a strong coupling between the matter system and photons of the radiation field. The latter can be the case within an optical resonator.In this thesis, additional effects of a quantized radiation field are inves tigated on a pump-probe experiment for detecting the optical Stark effect. One significant effect is that the lineshape of the shifted resonance displays the photon statistics of the pump field. For small pump detuning probe gain results in a frequency regime where the semiclassical treatment predicts absorption. This effect is refered to nonclassical gain. For larger ensembles of two-level systems, additional substructures and resonances appear within the probe absorption spectrum. Also non- diagonal elements of the field density matrix can be detected in such an experiment. In order to describe a more complex matter systems, the optical Stark effect has been treated in terms of a density matrix approach with quantized radiation fields. For a quantitative description of nonclassical gain, higher correlation terms had to be treated properly. Moreover, conserved quantities were taken into account in approximate decouplings. The density matrix approach was applied to the description of the optical Stark effect on impurity-bound excitons in semiconductors. These systems are of high interest as their narrow resonances might allow the demonstration of fine effects of the quantized radiation field.
Satter, Md Mahbub. "Design and theoretical study of Wurtzite III-N deep ultraviolet edge emitting laser diodes". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53042.
Texto completoMonavarian, Morteza. "Beyond conventional c-plane GaN-based light emitting diodes: A systematic exploration of LEDs on semi-polar orientations". VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4198.
Texto completoZippel, Jan. "Gepulste Laserabscheidung und Charakterisierung funktionaler oxidischer Dünnfilme und Heterostrukturen". Doctoral thesis, Universitätsbibliothek Leipzig, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-100358.
Texto completoAshkarin, Ivan. "Few-body Förster resonances in Rydberg atoms for the implementation of quantum computing". Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASP199.
Texto completoApplication of few-body Förster resonances for implementation of multiqubit quantum gate circuits has been investigated. New types of three-atom Borromean transitions based on the relay atom have been proposed and numerically studied. In particular, a Stark-controlled non-isolated three-atom Förster resonance between high-lying n = 80, 81, 82 S − P states of Rb atoms isolated in individual optical traps has been modeled. Isolated three-atom Förster resonance has also been demonstrated for n = 70, 71 states of Rb atoms. The resonances were investigated in a fixed spatial configuration, allowing us to demonstrate the coherent population and phase dynamics of the collective states involved. Three-qubit Toffoli gates schemes have been developed and numerically modeled based on the demonstrated resonances. Also, a generalized doubly controlled phase CCPHASE gate scheme has been developed based on the radiofrequency-induced three-body Förster resonance. Additionally, a similar quantum gate scheme has been proposed based on two-atom RF-induced Förster resonance with controlled displacement. The fast performance and high fidelity of the proposed schemes, as well as their potential robustness to errors, allow us to expect a successful experimental implementation in the near future
Hakobyan, Vahe. "Laser control of quantum systems by ultrafast parallel adiabatic passage : application to high fidelity population transfer, state selectivity, and superposition of states". Phd thesis, Université de Bourgogne, 2011. http://tel.archives-ouvertes.fr/tel-00705504.
Texto completoVakarin, Vladyslav. "Composants optoélectroniques à base d'alliages SiGe riches en Ge pour le proche et moyen infrarouge". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS473/document.
Texto completoToday optical interconnects have overpassed wires on long, mid and short distances on the telecommunication field. Silicon photonics have known such a development that even inter and intra chip communications progressively become optical. However, the multiplication of data access terminals and the constant increase of data consumption force new components with even lower power consumption to appear. In this context, low power consumption components based on Ge/SiGe quantum wells have been developed. Until now, the use of Ge/SiGe quantum wells has been only limited to electroabsorption modulators. The first part of my thesis was dedicated to the study of a new kind of active region based on coupled Ge/SiGe quantum wells. This work led to the demonstration of giant electrorefractive effect in these structures. The active region based on coupled quantum wells gives a refractive index variation of 2.3×10-3 under a bias of only 1.5 V. The use of this effect for the development of integrated optical modulators needed the development of main building blocks to obtain interferometric structures. Compact bends and Mach Zehnder interferometers have been designed, fabricated and successfully characterized. The sensitivity to the polarization of these structures was evaluated with numerical simulations and polarization insensitive structures were designed. Then, an integrated electrorefractive modulator has been designed and fabricated which needed the development of a new technological process. The first charaterization results are presented. The perspectives of this work are the realization of an efficient modulator with switching voltage lower than 2V. The field of application of photonic integrated circuits is not only limited to the telecommunications. The approach based on integrated optics is also very promising for the identification and analysis of surrounding chemical species. Mid infrared spectral region is particularly suitable for this purpose as it contains specific absorption fingerprints of different chemical species. The use of photonic integrated circuits on silicon substrate allows to develop performant, compact and low cost spectroscopic systems. The second part of my thesis was focused on the development of wideband photonic platform based on Ge-rich Si1-xGex waveguides. Wideband waveguides between 5.5 and 8.5 µm were experimentally demonstrated which made possible the developpement of more complex structures such as MMIs or ultra-wideband Mach Zehnder interferometers. The same device has a theoretical bandwidth of 3.5 µm in TE polarization and of one octave in TM polarization. The operation was experimentally demonstrated between 5.5 and 8.6 µm and is only limited by laser spectral range. This work paves the way for future development of ultra-wideband spectroscopic systems on Ge-rich Si1-xGex platform. The last part of this work concerned second harmonic generation in Ge/SiGe quantum wells for mid infrared spectroscopic systems. First test devices have been designed and fabricated
Langhammer, Christoph. "Kalorimetrische Untersuchungen zu Magnetismus, Supraleitung und Nicht-Fermi-Flüssigkeits-Effekten in Systemen mit starken Elektronenkorrelationen". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2000. http://nbn-resolving.de/urn:nbn:de:swb:14-991032056140-31582.
Texto completoZhou, Qi-Wei y 周其緯. "Quantum Confined Stark Effect and Its Application to Modulator". Thesis, 1992. http://ndltd.ncl.edu.tw/handle/04525666300823240556.
Texto completoJou, C. w. y 周其緯. "Quantum Confined Stark Effect And Its Application To Modulator". Thesis, 1992. http://ndltd.ncl.edu.tw/handle/93263782776759759227.
Texto completo國立成功大學
電機工程研究所
80
The purpose of this thesis is to investigate the mechanism of the quantum well self-electro-optic effect device (SEED): Quantum confined Stark effect and the theory of binding exciton in a quantum well will be dicussed. First, according to the one-dimension time-independence Schrodinger equation, the discrete energy levels and the wave function in the quantum wells are calculated by a new numerical analysis method. Second, a variational method with separable trial funtion is employed to evaluate the binding energy of an exciton in a quantum well. Then,the position of the exciton absorption peads with applied field perpendicular to quantum-well layers can be predicted. Finally, considering the theoretical model of exciton spectrum, the integrated intensity of the optical absorption spectrum of ground-state electron-heavy-hole exciton resonance both in III-V and II-VI semiconductor quantum wells are calculated. It is found that II-VI quantum-wells have higher room-temperature excitonic saturation. The optimal device parameters of the SEEDs can be then determined.
Ferrari, Christian. "Aspects of two dimensional magnetic Schrödinger operators: quantum Hall systems and magnetic Stark resonances". Phd thesis, 2003. http://tel.archives-ouvertes.fr/tel-00003144.
Texto completoChang, Che-Wei y 張哲瑋. "Quantum Confined Stark Effect (QCSE) in Silicon-Germanium (SiGe) Electro-Absorption Devices". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/68912652674397154480.
Texto completo國立臺灣大學
電子工程學研究所
96
Optical communications have dominated the intermediate to long distance data transmission and also gradually replaced the metal interconnects for the short-distance links. The decreasing device size in silicon chips increases the interconnect resistance and hence degrades the system speed severely, thus the optical interconnects is one of the solutions to enable high-speed and high-capacity chip-scale communication technology. The high-speed external optical modulator is one of the key components routinely used in today’s optical communications. The Quantum confined stark effect (QCSE) – one of the most effective modulator operating theorems – can enable high-speed external modulation with low operation voltage. The QCSE had been demonstrated in the germanium quantum well system grown on silicon and would enable optical interconnects integrated with silicon chips. The QCSE at room temperature with thick quantum well was investigated in this thesis study. Since both silicon and germanium are indirect bandgap materials, there exist not only direct gap absorption transition but also indirect gap absorption with lower transition energy which leads to the background absorption. An electro-absorption measurement system was setup to study the QCSE as well as the direct and indirect absorption. The thick quantum well structure exhibits electroabsorption effect in the C-band and has lower quantum well energy, weaker exciton, and less indirect absorption. Besides, the simulations based on the tunneling resonance method are discussed.
Su, Vin-Cent y 蘇文生. "Quantum-Confined Stark Effect of InGaN-Based Light-Emitting Diodes Influenced by Patterned Sapphire Substrates". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/54535530387616521521.
Texto completoSchmidt, Johannes. "THz pump-probe spectroscopy of the intersubband AC-Stark effect in a GaAs quantum well". 2019. https://tud.qucosa.de/id/qucosa%3A38238.
Texto completoIn dieser Arbeit berichten wir über die starke Licht-Materie Wechselwirkung in 3-Niveau system anhand eines einzelnen, breiten GaAs/AlGaAs Quantentopfes. Insbesondere untersuchen wir den AC-Stark Effekt und beobachten eine Aufspaltung des Absorptionsspektrums durch das Autler-Townes Dublett und das Mollow Triplett. Im direkten Vergleich mit vorangegangenen Arbeiten zeigen wir zum ersten Mal ein reines THz Anrege-Abfrage Experiment mit Frequenzen unterhalb des Reststrahlenbandes. Weiterhin beobachten wir eine starke Frequenzverschiebung der Absorptionsenergie des ersten Intersubbandübergangs in Abhängigkeit von der Ladungsträgerdichte im Quantentopf. Sowohl das Autler-Townes Dublett als auch die Verschiebung der Absorptionsfrequenz ermöglichen potentielle Anwendung im Bereich der THz-Modulation. Im Bereich der starken Licht-Materie Wechselwirkung sind viele interessante Effekte beobachtbar wie Rabi Oszillationen, coherent population trapping, Lasern ohne Inversion, elektromagnetisch induzierte Transparenz (EIT) und der AC-Stark Effekt. Unser Quantentopf stellt ein 3-Niveau System dar, in welchem wir eine Aufspaltung der Absorption bezüglich des ersten und zweiten Intersubbandübergangs beobachten. Insbesondere für den ersten Intersubbandübergang ist auch eine Absorptionsaufspaltung durch den EIT Effekt vorhergesagt, während der zweite Intersubbandübergang durch ein starkes, elektrisches Wechselfeld angeregt wird. Es stellt sich dann die Frage, wodurch sich die Effekte EIT und Autler-Townes splitting unterscheiden, weil beide durch ein spektrales transparentes Fenster gekennzeichnet sind. Die von uns gewählte Methode verknüpft schmalbandige, starke elecktrische Wechselfelder im THz-Bereich eines freien Elektronen Lasers und breitbandigen THz-Pulsen, welche durch nichtlineare optische Effekte in einem THz Zeit-Bereichs Spektroskopie Aufbaus erzeugt werden. In dieser einzigartigen Konfiguration führen wir zeitaufgelöste Anrege-Abfrage Spektroskopie Experimente durch, in dem wir den zweiten Intersubbandübergang bei 3, 4 THz nahezu resonant anregen und das zweite und dritte Subband aufspalten. Mit breitbandigen THz Pulsen fragen wir dann die Absorptionsaufspaltung von ca. 0, 2 THz des ersten Intersubbandübergangs bei ≈ 2, 3 THz und des zweiten Intersubbandübergangs (Mollow-Triplett) ab. Nach Auswerten der Experimente und theoretischer Kriterien für die Unterscheidung zwischen EIT und Autler-Townes splitting schlussfolgern wir, ein Autler-Townes Dublett zu beobachten.
Chen, Yen-Pu y 陳彥蒲. "Manipulation of Quantum Confined Stark Effect in GaN-Based Light-Emitting Diode by Microstructure on Substrate". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/73983041915651756351.
Texto completo國立臺灣大學
電子工程學研究所
103
GaN-based light-emitting diodes (LEDs) are typically grown on c-plane sapphire, or even patterned sapphire substrates (PSSs). In the same growth condition, we adopt wet etching to fabricate our PSSs with structure depth about 0.5µm instead of dry etching with depth up to 1.6µm. However, we find that the quantum-confined Stark effect (QCSE) can be reduced by changing the geometry of PSSs. Moreover, we have found a probable key parameter which dominates the QCSE magnitude, so that we can predict a probable range to further minimize the QCSE. In the device level, we demonstrate that by reducing QCSE, the optical performance of LED devices such as internal quantum efficiency (IQE) and external quantum efficiency (EQE) can be enhanced, but efficiency droop is larger. After our analysis through the differential of EQE, the efficiency droop should be attributed to the consequence of increasing IQE. In the end, in comparison to the LED devices grown on conventional PSSs, our light output power (LOP) and EQE can reach up to 95% of the conventional one. Therefore, the reduction of QCSE is effective to enhance the performance of LEDs, and it’s potential to be an alternative to fabricate LEDs without changing the crystal growth conditions.
"Electronic, Spin and Valley Transport in Two Dimensional Dirac Systems". Doctoral diss., 2017. http://hdl.handle.net/2286/R.I.43929.
Texto completoDissertation/Thesis
Doctoral Dissertation Electrical Engineering 2017
COLLISTER, ROBERT A. "Studies of Highly Polar Atomic and Molecular Systems: Quantum Dynamics and the Route to Experimental Investigations". Thesis, 2009. http://hdl.handle.net/1974/5353.
Texto completoThesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2009-12-09 16:49:41.184
Chang, Yu-Chen y 張語宸. "Stark effects in optical anisotropies of self-assembled quantum dots". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/37300243323105818157.
Texto completo國立交通大學
電子物理系所
99
This thesis theoretically investigates the electronic structures and optical properties of InAs/GaAs self-assembled quantum dots under external electric fields by using six-band Luttinger-Kohn k?況 theory. First, the single-particle (conduction electron or valence hole) spectra of box, pyramid, and truncated-pyramid shaped quantum dots are calculated by using finite difference method. The strain distributions in and out of dots are computed by using finite element software package Comsol multiphysics®. Based on the single particle spectra, optical polarization degree of the ground states of an exciton photo-generated in a quantum dot is calculated by using Fermi’s golden rule. The strain calculations show that the effective confining potential for heavy-hole in a strained dot is governed by out-of-plane strain while the one for light-hole by in-plane strain. The theoretical results show that, compared with box and truncated-pyramid shaped dots, heavy- and light-hole coupling is significantly increased in a pyramid-shaped dot because of larger hydrostatic strain (smaller bi-axial strain) in the narrow upper region of the nano-pyramid. With more light-hole component, larger optical polarization degree is observed for high pyramid-shped dots. Furthermore, the light-hole component in a hole ground state can be significantly changed by applying an external electric field along the growth-axis. As a result, it is found that the stark effect could increases the polarization degree of a high pyramid dot by 5% by applying an electric field up to 200 KeV/cm.
Shen, Kai-Lun y 沈凱綸. "Quantum Chemistry Calculation of Substituent Effect、Stack Effect and Hydration Effect of Double Proton Transfer on Amide and Acid Molecules". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/nqn627.
Texto completo國立臺灣大學
應用力學研究所
104
We studied the N-H...O=C and O-H...O=C type hydrogen bonds by substituting alkyl groups on amide and acid molecules. All the quantum chemistry calculations were performed at Gaussian 09 software to optimize individual keto or enol structures and search the transition state of proton transfer reaction. Meanwhile,we use the IRC(Intrinsic reaction coordinate) method to plot the reaction path in order to obtain the energy barrier. In addition, the PSI4 software was utilized through the SAPT method to decompose the intermolecular interaction into several physically meaningfull terms, to discuss the effect of alkyl groups on the proton transfer reaction. For the stack effect, we use amide and acid molecules in planar structures and use several vertically stacked layers to observe the effect of stacking on proton transfer reaction. Six-carbon ring on the outside is used to bond each layers, similar to the peripheral backbone in DNA double helix. The energy barrier of proton transfer under different stacking structures was also discussed. We also consider the hydration effect on amide and acid of proton transfer reaction. Recent studies have shown that water molecules could hamper direct proton transfer between nitrogenous bases, but it plays the role of proton donor and acceptor during the reaction. Therefore, water molecules can form hydrogen bonding network to be involved in the proton transfer process. In such cases we use amide and acid molecule as a simplified model for analysis. At the same time, the configuration of waters surrounding the dimer or clamping in the hydrogen bonds of the dimer has been discussed.
Lee, Chin-hsi y 李進希. "Investigating Integer Quantum Hall effect in Kagomé and star lattice by Yasuhiro Hatsugai’s method". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/24tkuw.
Texto completo國立中山大學
物理學系研究所
103
Since the single layer graphene are observed by Andre Geim and Konstantin Novoselov, the quantum phenomena emerging from graphene as attracted many physicists’s attentions in the two dimensional lattice structure. One of the important quantum phenomena is the unconventional quantum Hall effect which the Hall plateau (Chern number pattern) does not show successive integers but only odd integers. However, there are some other problems to calculate the quantum Hall conductivity, such as the determination of the Chern number pattern from a specific lattice structure and the reduction of the computational time. Motivated by these issues, I use Yasuhiro Hatsugai’s topological approaches to investigate the quantum Hall effect of other lattices. I use Hatsugai’s method to calculate the quantum Hall conductivity in two different lattices: Kagomé and star lattices. I find that the Dirac-like regions of quantum Hall conductivity also exists in both Kagomé and star lattices, which is similar to graphene. Unlike the graphene, the star lattice shows complicated Chern number structure in the electron-hole like regions. Hopefully, the Chern number pattern of the star lattice predicted by us can be determined by experiments in the near future.
Li, Chao-Chin y 李肇晉. "The Absence and Presence of Quantum Confined Stark Effects in Single InGaN Nanodisks with Different Disk Thicknesses". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/dma8hk.
Texto completo國立清華大學
物理學系
105
Ⅲ-nitride semiconductor heterostructures have been widely applied for blue and white light LEDs. However, the internal piezoelectric field can produce large quantum confined stark effects (QCSE), and reduce the light emission quantum efficiency. Here, we use InxGa1-xN (InGaN) nanorod heterostructures grown by plasma-assisted molecular-beam epitaxy (PA-MBE) for experimental investigation of QCSE. We have measured the micro photoluminescence (PL) spectra for the shift of PL peak energy versus optical pumping power intensity and time-resolved PL spectra for exciton measurements using InGaN nanodisk samples with different nanodisk thicknesses. We found that the thickness of InGaN nanodisk plays a significant role in the observation of QCSE.
Abraham, Nithin. "Van der Waals Heterojunctions for Emerging Device Applications". Thesis, 2022. https://etd.iisc.ac.in/handle/2005/6049.
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