Topic
Quantum well
About: Quantum well is a research topic. Over the lifetime, 44627 publications have been published within this topic receiving 674023 citations. The topic is also known as: QW & quantum potential well.
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TL;DR: In this paper, the authors investigated the possibility of mode locking a semiconductor laser at millimeter wave frequencies approaching and beyond 100 GHz and found that there are no fundamental theoretical limitations in mode locking at frequencies below 100 GHz.
Abstract: The possibility of mode locking a semiconductor laser at millimeter wave frequencies approaching and beyond 100 GHz was investigated theoretically and experimentally. It is found that there are no fundamental theoretical limitations in mode locking at frequencies below 100 GHz. At these high frequencies, only a few modes are locked and the output usually takes the form of a deep sinusoidal modulation which is synchronized in phase with the externally applied modulation at the intermodal heat frequency. This can be regarded for practical purposes as a highly efficient means of directly modulating an optical carrier over a narrow band at millimeter wave frequencies. Both active and passive mode locking are theoretically possible. >
127 citations
TL;DR: In this article, temperature-dependent photoluminescence (PL) spectroscopy as-grown GaInNAs, InGaAs, and GaAsN quantum wells (QWs) embedded in a GaAs matrix was investigated.
Abstract: We have investigated by temperature-dependent photoluminescence (PL) spectroscopy as-grown GaInNAs, InGaAs, and GaAsN quantum wells (QWs) embedded in a GaAs matrix. The evolution of the PL peak position and of the PL linewidth shows evidence of a strong carrier localization for the GaInNAs QWs only. The high delocalization temperature, in the 150 K range, indicates the presence of a high density of possibly deep-localizing potential wells. In addition, a higher density of nonradiative recombination centers appears to result in stronger carrier localization. Transmission electron microscopy reveals well defined, flat interfaces, in these comparatively high N-content (yN∼0.04–0.05) QWs. Our results thus demonstrate that the origin of localization in GaInNAs QWs is the concomitant presence of both In and N, which may result in strain and/or composition fluctuations.
127 citations
Proceedings Article•
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TL;DR: In this paper, Veron et al. developed a statistical model of incoherent field amplification in the presence of Kerr nonlinearity and showed that gain broadening takes over the expected gain narrowing effect.
Abstract: optical fiber (SOF),’ smoothing by spectral dispersion (SSD),’ and smoothing by transverse spectral dispersion (STSD).3 SOF seems to be an efficient method concerning the limit contrast, shape, and control of the focal spot, and the smoothing of low spatial frequencies. But first experiences with SOF technique have shown a limitation in term ofthe amplification perf~rmance.~ In this paper we present recent results obtained on the backlighter beamline of the Phebus facility, which delivers up to 1.5 kJ at 1053 nm on a 19-cm diameter beam in a 1.3-11s square pulse. Figure 1 shows the output energy as a function of input energy for different configurations. The upper curve corresponds to a monochromatic pulse, the intermediate one to a spatially coherent broadband pulse (Ak = 1.2 nm), and the lower one to the incoherent pulse (Ak = 0.6 nm) obtained by the SOF technique. It shows a loss of 40% for the performance in the latter case. We first analyze the amplification of spatially coherent monochromatic pulses versus broadband noisy pulse. Figure 2 shows the observed output amplified spectra versus input energy. The main observation is that gain broadening takes over the expected gain narrowing effect. To explain these data, we have developed a statistical model of incoherent field amplification in presence of Kerr n~n l inea r i ty .~ If we use as a parameter the usual B integral, we find that the spectral broadening cx = Ak,utput/AX,,put is approximately given by cx = d1 + 2 B 2 and is associated to a gain loss estimated to be 2e2B2, where E = TJT , << 1, T2 being the amplifymg medium dephasing time and 7, the broadband pulse coherence time. This corresponds in our experimental case to a decrease of 10% for the maximum input of Fig. 1 in good agreement with the experimental data. The lower curve of Fig. 1 represents the amplification of an incoherent beam, which shows amuch more important decrease ofperformance. These data are compared with a model that takes into account the speckled characteristics of the light. We shall discuss the implication of this model and in particular the importance of controlling the intensity contrast of the beam in the amplifier. Recent data with broader bandwidth (8 nm) will also be presented. *Centre de Mathtmatiques Appliqutes, CNRS URA 756, Ecole Polytechnique, 91 128 Palaiseau Cedex, France **Also with Laboratoire pour l’litilisation des Lasers Intenses, CNRS UMR 100, Ecole Polytechnique, 91 128 Palaiseau Cedex, France 1. D. Veron, H. Ayral, D. Husson, 0. Martin, B. Meyer, M. Rostaing, C. Sauteret, Opt. Commun. 65 (1) (1988). S. Skupsky, R. W. Short, T. Kessler, R. S. Craton, S. Letzring, J. M. Soures, J. Appl. Phys. 66 (8) (1989). 3. LLE Review 36. 4. D. Veron, G. Thiell, C. Gouedard, Opt. Commun. 97,259-271 (1996). 5. “Amplification of broadband incoherent light in homogeneously broadband media in presence of Kerr nonlinearity,” J. Garnier, C. Gouedard, 0. Bonville, D. Boisgard, J. P. Fouque, A. Migus, submitted. 2.
127 citations
TL;DR: The perovskite quantum-well films showed strong exciton absorption at around 2.4 eV and sharp exciton emission even at room temperature, and the X ray diffraction measurement on the vacuum-deposited films demonstrated that the layer structure was oriented parallel to the film plane as discussed by the authors.
Abstract: Oriented thin films of layered perovskite compounds (RNH3)2PbI4, which possess a quantum well structure where a two-dimensional semiconductor layer of PbI4 and an organic ammonium layer of RNH3 are alternately piled up, were found to grow in a self-organizing manner on fused quartz substrates through the simple dual-source vapor deposition of organic ammonium iodide RNH3I and lead iodide PbI2. The perovskite quantum-well films showed strong exciton absorption at around 2.4 eV and sharp exciton emission even at room temperature. Further, the X ray diffraction measurement on the vacuum-deposited films demonstrated that the layer structure of the vacuum-deposited film was oriented parallel to the film plane.
127 citations
TL;DR: In this article, a semi-insulating multiple quantum well was proposed to combine the holographic properties of the photorefractive effect with the large resonant optical nonlinearities of quantum-confined excitons.
Abstract: We use semi-insulating multiple quantum wells to combine the holographic properties of the photorefractive effect with the large resonant optical nonlinearities of quantum-confined excitons. GaAs–AlGaAs multiple-quantum-well structures are made semi-insulating by proton implantation. The implant damage produces defects that are available to trap and store charge during transient holographic recording by means of coherent excitation. The advantages of charge storage and resonant optical nonlinearity combine to produce new optical devices with large sensitivities. The potential use of these devices for image processing is demonstrated by using the Franz–Keldysh effect in four-wave mixing at wavelengths near 830 nm.
126 citations