VOLTAGE TUNABLE MULTIPLE-QUANTUM-WELL DISTRIBUTED-FEEDBACK FILTER WITH AN ELECTRON-BEAM WRITTEN SCHOTTKY GRATING

A novel optoelectronic filter with voltage-tunable transfer characteri stics has been developed and implemented in a multiquantum well wavegu ide device. By virtue of the quantum-confined Stark effect, the refrac tive index in quantum wells at the periphery of a guiding region can b e given a periodicity in the guiding direction by application of a bia s on an electron-beam patterned Schottky grating atop the guide. If th e period of the Schottky grating and associated index profile satisfie s the Bragg condition, as in a resonant distributed feedback structure , band-reject filtering results. Altering the bias on the Schottky gra ting changes the refractive index in the wells, thereby providing tuna bility of the wavelength at which Bragg diffraction occurs.