Title :
Pre-illumination to control the active trap density in a semi-insulating MQW device
Author :
Canoglu, Ergun ; Garmire, Elsa ; Lahiri, I. ; Nolte, D.D. ; Melloch, M.R.
Author_Institution :
Thayer Sch. of Eng., Dartmouth Coll., Hanover, NH, USA
fDate :
10/1/1998 12:00:00 AM
Abstract :
The trap density in a photorefractive semi-insulating quantum-well (QW) device can be dynamically adjusted for optimum sensitivity by passivating some of its traps with photocarriers from a pre-illumination pulse. By reducing the effective trap density with pre-illumination, we demonstrate that the carrier drift length can increase, causing more than an order of magnitude increase in device sensitivity by increasing the number of QW´s screened per carrier. Too much pre-illumination, on the other hand, decreases four-wave mixing diffraction efficiency, due to lateral drift. The optimum trap density enables higher sensitivity while maintaining high-resolution operation. Pre-illumination can also be used to speed up grating erasure by increasing the electron-hole recombination probability
Keywords :
diffraction gratings; electro-optical modulation; electron-hole recombination; high-speed optical techniques; multiwave mixing; photorefractive effect; semiconductor devices; semiconductor quantum wells; sensitivity; spatial light modulators; active trap density; carrier drift length; control; device sensitivity; effective trap density; electron-hole recombination probability; four-wave mixing diffraction efficiency; grating erasure; high-resolution operation; lateral drift; optimum sensitivity; optimum trap density; photocarriers; photorefractive semi-insulating quantum-well device; pre-illumination; pre-illumination pulse; semi-insulating MQW device; trap density; Absorption; Electron traps; Four-wave mixing; Gratings; Optical modulation; Photorefractive effect; Quantum well devices; Radiative recombination; Refractive index; Spatial resolution;
Journal_Title :
Quantum Electronics, IEEE Journal of
