Transport Modeling Of Multiple Quatum Well Optically Addressed Spatial Light Modulators

Transport Modeling of Multiple-quatum-well Optically Addressed Spatial Light Modulators

Transport Modeling of Multiple-Quantum-Well Optically Addressed Spatial Light Modulators

Optically addressed spatial light modulators are essential elements in any optical processing system. Applications such as optical image correlation, short pulse auto-correlation, and gated holography require high speed, high resolution devices for use in compact, high throughput systems. Other important device criteria include ease of fabrication and operation. In this work we study the transport dynamics of a new kind of optically addressed spatial light modulator that uses semi-insulating or intrinsic quantum-well material to produce high performance devices without the need for pixellation or complicated device design. In response to an incident intensity pattern, basic device operation occurs through the screening of an applied voltage via the optical generation, transport, and trapping of photocarriers. A field pattern which mimics the incident intensity pattern is produced by the screening process. This generates strong index and absorption holograms via the quantum confined Stark effect. These holograms can be read out simultaneously with a probe beam to provide dynamic read/write operation. Overall device performance is determined by the transport of photocarriers during the field screening process. We have developed a transient, two-dimensional drift-diffusion model to describe both free and well-confined carrier transport as well as nonlinear effects such as velocity saturation and field-dependent carrier emission from quantum wells. Various analytical and numerical results for the internal carrier and space charge distributions, different screening regimes, and relative carrier contributions to the screening process are given. An experimental characterization of a GaAs/AlGaAs device using optical transmission and photocurrent techniques is also presented and used to verify the main results of the transport model. Analytical and numerical analyses of various transport effects that limit the resolution are also given.

Photorefractive Effects, Materials, and Devices