Heterostructure Acoustic Charge Transport (HACT) Spatial Light Modulators (SLMs) for 3-D Parallel Optical Memory Interconnects

This proposal focuses on the development of heterostructure acoustic charge transport (HACT) Spatial Light Modulator (SLM) structures, which potentially address a larger number of pixels with substantially fewer interconnects, as input and output devices for a 3-D volume optical memory. Unlike other types of SLMs, HACT addressing of a 10(6) pixel array requires only 3x1024 interconnects in place of 1024x1024 connections. In addition, HACT modulators operate in 100-1,000 MHz range resulting in access time in nanoseconds. An important objective is to develop a design and implementation methodology which would interface HACT-SLMs to various types of 3-D volume storage systems. We intend to investigate compatibility with different physical mechanisms used in the realization of optical memory involving phenomena such as two-photon absorption in organic photochromic materials, hole burning, and phase holograms.Recent developments in Multiple Quantum Well (MQW) Spatial Light Modulators (SLMs) has made them the focus of high performance optical signal processing systems used for correlators, optical computing, interconnects, and optical image processing applications. Tunable high contrasts of 1200:1 have been reported by our group in InGaAs-GaAs single Fabry-Perot cavity MQW SLM structures operating at 980 nm. High speed operation in the range of 37-40 GHz have been demonstrated for single pixels (16umx20um) in GaAs/InP based MQWs. However, significant progress has yet to be made in the area of pixel addressing to realize the full potential of these devices. As the number of pixels incrases in a SLM, the addressing becomes complex and limits the size of an array. For example, in a 1024x1024 pixel array, one needs at least two interconnects per pixel. Pixel addressing employing heterostructure acoustic charge transport (HACT) in modulation doped high carrier mobility channels (in HQW SLMs) simplifies the complexity to 3x1024 interconnects in electrically addressed devices. The recent fabrication of HACT channels on Fabry-Perot structures, by the University of Connecticut (UConn) and United Technologies Research Center's (UTRC) team, has demonstrated charge transport for several millimeters covering over 20 pixels with a charge transfer efficiency of about 0.9. Improved design and fabrication methodology is needed to accomplish the full potential of HACT addressing which has been demonstrated to transport charges over few centimeters (i.e. well over 1024 pixels) in electroni