- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Amplified luminescence of heavily doped Al <sub/>x</sub> Ga <sub/>1-x</sub> N structures under optical pumping
摘要： Spectral, temporal, and polarisation characteristics of luminescence of heavily doped AlxGa1 – xN films on a sapphire substrate are studied under pulsed pumping at the wavelength l = 266 m. Spectra of spontaneous emission related to donor – acceptor transitions are inhomogeneously broadened with the FWHM of above 0.5 eV and cover the entire visible range. Spectra of radiation emitted from an edge of investigated structure comprise several narrow-band equidistant components, each of them being split to TE and TM modes with mutually orthogonal polarisations. This is related to plane waves propagating inside a plane waveguide along a zigzag path in the conditions of total internal reflection from waveguide surfaces. The optical gains measured for Al0.5Ga0.5N/AlN at l ? 510 nm, Al0.74Ga0.26N/AlN at l ? 468 nm, and AlN/Al0.6Ga0.4N/AlN/Al2O3 at l ? 480 nm were, respectively, ~70, 20, and 44 cm–1. The luminescence quantum efficiencies measured for Al0.74Ga0.26N, Al0.65Ga0.35N, and Al0.5Ga0.5N films are, respectively, 0.79, 0.49, and 0.14; the transition cross sections calculated at emission band centres are ~10–18 cm2.
关键词： spontaneous emission,luminescence,gain,optical pumping
更新于2025-09-23 15:21:01
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604-nm high-order vortex beams directly generated from a Pr:YLF laser with a cavity-loss-induced gain switching mechanism
摘要： In this work, we demonstrated, for the ?rst time to the best of our knowledge, high-order vortex beams at 604 nm that were directly emitted from a Pr:YLF crystal laser. By combining a blue-diode-pumped v-type cavity for controllable Gouy phase introduction and o?-axis crystal rotation for high-order HG modes generation, topological charged 604-nm vortex lasers were attained up to the third order. Furthermore, the vortex beams were found to be lasing at 604 nm that was often deemed less prone to lase compared with 607-nm in the same energy manifold. By a detailed spectroscopic study and rate equation analysis, we proposed and con?rmed that the 604-nm transition of Pr:YLF crystal could be favorable in the vortex beam generation by a cavity-loss-induced gain switching process, in which the net gain at 604-nm could surpass that of 607-nm as the cavity loss was amassed beyond a threshold value.
关键词： Interference,Optical pumping,Laser modes,Optical resonators
更新于2025-09-23 15:19:57
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Metal Vapor Lasers
摘要： The milestones in the development of researches connected with metal vapor lasers, which have been carried out at V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, since its first days are considered. Some of the most interesting fundamental and applied results are presented. A fairly extensive list of related works, published mainly in the past twenty years, is given.
关键词： brightness amplifier,active thermal insulation,active impurity generator,optical pumping,metal vapor lasers,laser efficiency,metal halides,active optical systems,inner reactor
更新于2025-09-23 15:19:57
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Rapid Optical Spin Initialization of a Quantum Dot in the Voigt Geometry Coupled to a Two-Dimensional Semiconductor
摘要： We study the interaction of a quantum dot in the Voigt con?guration with a laser pulse and particularly analyze the potential for rapid spin initialization by putting the quantum dot near a molybdenum disul?de (MoS2) monolayer. The MoS2 monolayer in?uences the spontaneous decay rates of the quantum dot, leading to anisotropically enhanced decay rates, for the quantum dot’s electric dipole moments parallel and perpendicular to the layer. By solving the relevant density matrix equations, we ?nd that high spin initialization ?delity is obtained at short times. The ?delity is signi?cantly higher than when the quantum dot is in free-space vacuum. We examine two different cases of the interaction of the quantum dot with the applied optical ?eld. First, we use a continuous wave laser ?eld and determine for various quantum dot—MoS2 layer distances the ?eld strength that leads to acceptable ?delity levels. The effect of the quality of the MoS2 material on the ?delity of spin initialization is also examined. We also study the interaction of the quantum dot with a laser pulse and apply numerical optimal control to obtain the time-dependent ?eld strength, which leads to maximum ?nal ?delity for short time intervals. The latter approach gives bene?cial results in comparison to the continuous wave ?eld excitation.
关键词： spin initialization,quantum dot,Voigt geometry,optical pumping,Purcell effect,optimal control,spin dynamics
更新于2025-09-23 15:19:57
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Watt-Level CW Ti:Sapphire Oscillator Directly Pumped with Green Laser Diodes Module
摘要： A watt-level directly diode-pumped continuous-wave (CW) Ti:Sapphire oscillator was demonstrated for the first breakthrough by a high-power green laser-diode-pumped module employing the technologies of beam shaping, beam collimation, polarization beam combining, and fiber coupling. A 1.36-W output power and 10.6% of slope efficiency were obtained based on the double-concave (DC) cavity configuration. This is the highest CW output power from Ti:Sapphire (Ti:S) oscillator directly pumped by green laser diodes (LDs) reported so far.
关键词： Semiconductor laser arrays,Optical pumping,Optical design techniques,Diode lasers
更新于2025-09-19 17:13:59
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - <sup>15</sup> NH <sub/>3</sub> terahertz gas laser pumped by a mid-infrared quantum-cascade laser
摘要： We present an optically pumped terahertz gas laser, which is based on a distributed-feedback mid-infrared quantum-cascade laser as a pump source, a standing wave resonator, and 15NH3 as a gain medium.
关键词： optical pumping,15NH3,terahertz gas laser,mid-infrared,quantum-cascade laser
更新于2025-09-16 10:30:52
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Electron Population Dynamics in Optically Pumped Asymmetric Coupled Ge/SiGe Quantum Wells: Experiment and Models
摘要： n-type doped Ge quantum wells with SiGe barriers represent a promising heterostructure system for the development of radiation emitters in the terahertz range such as electrically pumped quantum cascade lasers and optically pumped quantum fountain lasers. The nonpolar lattice of Ge and SiGe provides electron–phonon scattering rates that are one order of magnitude lower than polar GaAs. We have developed a self-consistent numerical energy-balance model based on a rate equation approach which includes inelastic and elastic inter- and intra-subband scattering events and takes into account a realistic two-dimensional electron gas distribution in all the subband states of the Ge/SiGe quantum wells by considering subband-dependent electronic temperatures and chemical potentials. This full-subband model is compared here to the standard discrete-energy-level model, in which the material parameters are limited to few input values (scattering rates and radiative cross sections). To provide an experimental case study, we have epitaxially grown samples consisting of two asymmetric coupled quantum wells forming a three-level system, which we optically pump with a free electron laser. The benchmark quantity selected for model testing purposes is the saturation intensity at the 1→3 intersubband transition. The numerical quantum model prediction is in reasonable agreement with the experiments and therefore outperforms the discrete-energy-level analytical model, of which the prediction of the saturation intensity is off by a factor 3.
关键词： silicon–germanium heterostructures,intersubband photoluminescence,optical pumping,intersubband transitions,electron–phonon interaction,infrared spectroscopy,quantum wells,free electron laser,terahertz quantum cascade laser
更新于2025-09-16 10:30:52
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Slow and fast single photons from a quantum dot interacting with the excited state hyperfine structure of the Cesium D1-line
摘要： Hybrid interfaces between distinct quantum systems play a major role in the implementation of quantum networks. Quantum states have to be stored in memories to synchronize the photon arrival times for entanglement swapping by projective measurements in quantum repeaters or for entanglement purification. Here, we analyze the distortion of a single-photon wave packet propagating through a dispersive and absorptive medium with high spectral resolution. Single photons are generated from a single in(Ga)As quantum dot with its excitonic transition precisely set relative to the cesium D1 transition. the delay of spectral components of the single-photon wave packet with almost Fourier-limited width is investigated in detail with a 200 MHz narrow-band monolithic Fabry-Pérot resonator. Reflecting the excited state hyperfine structure of Cesium, “slow light” and “fast light” behavior is observed. As a step towards room-temperature alkali vapor memories, quantum dot photons are delayed for 5 ns by strong dispersion between the two 1.17 GHz hyperfine-split excited state transitions. Based on optical pumping on the hyperfine-split ground states, we propose a simple, all-optically controllable delay for synchronization of heralded narrow-band photons in a quantum network.
关键词： slow light,optical pumping,single-photon wave packet,quantum networks,quantum dot,cesium D1 transition,fast light,Fabry-Pérot resonator
更新于2025-09-16 10:30:52
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Deep UV laser at 249 nm based on GaN quantum wells
摘要： In this letter, we report on deep UV laser emitting at 249 nm based on thin GaN quantum wells (QWs) by optical pumping at room temperature. The laser threshold was 190 kW/cm2 that is comparable to state-of-the-art AlGaN QW lasers at similar wavelengths. The laser structure was pseudomorphically grown on a c-plane sapphire substrate by metalorganic chemical vapor deposition, comprising 40 pairs of 4 monolayer (ML) GaN QWs sandwiched by 6 ML AlN quantum barriers (QBs). The low threshold at the wavelength was attributed to large optical and quantum confinement, and high quality of the material, interface, and Fabry-P?rot facet. The emissions below and above the threshold were both dominated by transverse electric polarizations thanks to the valence band characteristics of GaN. This work unambiguously demonstrates the potentials of the binary AlN/GaN heterojunctions for high-performance UV emitters.
关键词： GaN quantum wells,deep UV laser,UV emitters,AlN/GaN heterojunctions,optical pumping
更新于2025-09-12 10:27:22
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Photoexcited terahertz conductivity in multi-layered and intercalated graphene
摘要： The synthesized graphene monolayer always has restrictions on its physical properties compared to the theoretical model of such material (e.g. area of single film, presence of defects, influence of substrate), so investigation of new graphene-based materials is required to implementation of real efficient terahertz devices. We report an experimental study showing that the conductivity dispersion spectra of modified graphene films (multilayer and intercalated with ferric chloride) in the range from 0.2 to 1.0 THz can be efficiently controlled using infrared optical pumping. It was found that the value of imaginary part of terahertz conductivity spectra of multilayer and intercalated graphene on dielectric substrates increases in absolute value with the rise of the pumping intensity, while the real part does not undergo significant changes. We employ a disorderly stacked multilayer graphene model which takes into account the attenuation of pumping intensity for theoretical analysis of the external optical pumping influence on the THz conductivity spectra of multi-layered graphene. Also, Drude–Smith model was applied to fit conductivity spectra of both multilayered and intercalated graphene samples. The models show adequate agreement with experimentally observed results.
关键词： Graphene,Optical pumping,Terahertz
更新于2025-09-12 10:27:22