Photorefractive p‐i‐n diode quantum well operating at 1.55 μm
ABSTRACT We demonstrate the performance of a semiconductor photorefractive p‐i‐n diode operating at 1.55 μm in the longitudinal quantum‐confined Stark geometry. The device structure consists of a semi‐insulating InP–GaInAs(P) multiple quantum well, sandwiched between two trapping regions, and embedded in a p‐n junction. In this structure, the measured output diffraction efficiency reaches 0.6%. This value is close to the output diffraction efficiency value estimated from electroabsorption measurements. © 1996 American Institute of Physics.
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ABSTRACT: Coded ultrafast optical pulses can be treated as one-dimensional (1-D) images in the time domain. We have converted spare-domain images into time-domain images using diffraction from dynamic holograms inside a Fourier pulse shaper, with photorefractive quantum wells (QW's) used as the dynamic holographic medium. We present several examples, in which amplitude or phase modulation of the hologram writing beams modifies the complex spectrum of the femtosecond output, resulting in a time-domain image. Both storage and processing of time-domain images can be achieved, depending on the hologram writing geometry and power densities. Time-domain processing operations such as edge enhancement, Fourier transform, and correlation are demonstratedIEEE Journal of Selected Topics in Quantum Electronics 04/1998; DOI:10.1109/2944.686739 · 3.47 Impact Factor
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ABSTRACT: The diffraction of 100-fs pulses from the static gratings of photorefractive quantum wells (QWs) produces diffracted pulses that are nearly transform-limited, despite the strong dispersion near the quantum-confined excitonic transitions. This quality makes the QW's candidates for use in femtosecond pulse shaping, although the currently limited bandwidth of the quantum-confined excitonic transitions broadens the diffracted pulses. Femtosecond electric-field cross correlation and spectral interferometry techniques completely characterize the low-intensity pulses diffracted from stand-alone photorefractive QWs, and from QWs placed inside a Fourier-domain femtosecond pulse shaperIEEE Journal of Quantum Electronics 01/1998; DOI:10.1109/3.644095 · 2.11 Impact Factor
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ABSTRACT: A transient, two-dimensional drift-diffusion model is developed for optically addressed spatial light modulators made with quantum-well materials. The transport of free and well-confined carriers is considered along with nonlinear transport effects such as velocity saturation, field-dependent carrier escape from quantum wells, and resonant absorption. In addition to full numerical solutions to the transport equations, analytical and simplified numerical solutions are developed to describe basic screening behavior and to give estimates of speed and resolution performance. In particular, a self-consistent small signal model is developed to justify the surface-charge picture often used to describe device operation. This model is also used to simulate grating formation and decay. It is found that the maximum screening rate and peak grating amplitude are achieved using vertical drift lengths much longer than the device length. A detailed analysis of resolution performance is also given in which the effects of transit time, carrier lifetime, and free and confined transport along the wells are simulated. For typical device parameters, the two main limitations to resolution performance are found to be anisotropic drift in the interior due to the quantum wells and transverse drift along the device interfaces. Two device designs are compared to assess the ability to optimize device performance by changing experimentally accessible parameters such as carrier lifetime and quantum-well escape rates. Resolutions down to 7 μm and frame rates of 100 kHz at 10 mW/cm2 are achieved. © 1997 American Institute of Physics.Journal of Applied Physics 02/1997; 81(5):2076-2088. DOI:10.1063/1.364259 · 2.19 Impact Factor