The resolution of distributed photorefractive multiple quantum well devices

Photorefractive multiple quantum well (PRMQW) devices can achieve simultane ously higher resolution and greater sensitivity by distributing several hig hly trapping low temperature growth (LTG) layers at different depths in the ir intrinsic region. This article extends a previously derived analytical m odel of PRMQW devices to distributed photorefractive devices (DPDs) that co nsist of a cascade of smaller MQW regions sandwiched between LTG layers. Th is enables an understanding of how multiple trapping layers affect the reso lution and sensitivity in these DPDs. In addition to an improvement in reso lution, the model predicts an enhancement in diffraction efficiency at smal l grating spacings as the number of subdevices increases for a fixed total DPD length. This result is of significance in designing compact image proce ssing systems that can operate at small grating periods but still be able t o achieve a large signal-to-noise ratio for image processing and sensing ap plications. (C) 2000 American Institute of Physics. [S0021-8979(00)00722-2] .