1 December 1991 Low-power optically addressed spatial light modulators using MBE-grown III-V structures
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Device approaches are investigated for O-SLMs based on MBE engineered III-V materials and structures. Strong photo-optic effects can be achieved in periodically (delta) -doped multiple quantum well (MQW) structures. The doping-defined barriers serve to separate and delay recombination of the photo-generated electron-hole pairs. One can use this photo-effect to change the internal field across the MQWs giving rise to quantum-confined Stark shift. Alternately, the photo-generated electrons can be used to occupy the quantum wells, which in turn causes exciton quenching and a shift of the absorption edge. Recent work has shown that both of these predicted photo-optic effects can indeed be achieved in such MBE engineered structures. However, these enhanced effects are still insufficient for high contrast modulation with only single or double pass absorption through active layers of practical thickness. We use the asymmetric Fabry-Perot cavity approach which permits extinction of light due to interference of light reflected from the front and back surfaces of the cavity. Modulation of the absorption in the active cavity layers unbalances the cavity and 'turns on' the reflected output signal, thereby allowing large contrast ratios. This approach is realized with an all-MBE- grown structure consisting of a GaAs/AlAs quarter-wave stack reflector grown over the GaAs substrate as the high reflectance mirror (approximately equals 0.98) and the GaAs surface as the low reflectance mirror (approximately equals 0.3). We use for our active cavities InGaAs/GaAs MQWs separated by npn (delta) -doped GaAs barriers to achieve sensitive photo-optic effect due to exciton quenching. High contrast modulation (> 60:1) is achieved with the Fabry-Perot structures using low power (< 100 mW/cm2) InGaAs/GaAS quantum well lasers for a write signal.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Joseph L. Maserjian, Anders G. Larsson, "Low-power optically addressed spatial light modulators using MBE-grown III-V structures", Proc. SPIE 1562, Devices for Optical Processing, (1 December 1991); doi: 10.1117/12.50773; https://doi.org/10.1117/12.50773

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