Abstract: An intersub-valence band quantum well detector (52), comprising alternating quantum wells (30') and barriers (32'), provided with differential strain permits obtaining hole mean free paths similar to the electron. Consequently, the gain and responsivity should dramatically increase. In addition, the absorption coefficient should increase, while the noise current should decrease; thus, the quantum efficiency and the detectivity (D*) should increase, compared to a detector without the added differential strain.

Abstract: Enhanced energy transfers are achieved between optical beams by operating at wavelengths in the near-bandgap region of a photorefractive material, and employing an electrorefractive effect previously proposed only for single beams. An electric field is applied across a photorefractive medium of sufficient intensity to induce an electrorefractive coupling and consequent energy transfer between the beams. Gain enhancements are possible by orienting the photorefractive medium to obtain an electro-optic as well as an electrorefractive effect, and by a moving grating technique. The direction of energy transfer between the beams is controlled by the electric field direction, and can be reversed by reversing the field. Operation in the infrared region is made possible with semi-insulating materials. Applications include optical switches, amplifiers and phase conjugators.

Abstract: A semiconductor laser of the heterostructure type is grown on a p-type substrate and has a plurality of p-type active layers. In a preferred embodiment, the active layers are grown by liquid phase epitaxy from a single melt which is maintained just below its equilibrium temperature and is cooled very slowly during deposition. As a result, the active layers are substantially identical in composition and have a very low lattice mismatch. They emit light at characteristic wavelengths within 50 angstroms of each other, indicating that their modal gain envelopes coincide. This condition minimizes the threshold current.

Abstract: Disclosed is a GaA1As laser diode wherein an abrupt etch step in the waveguide layer forms a third mirror. The structure is a large optical cavity double heterostructure laser having a relatively long active cavity and a relatively short passive cavity. Output is temperature and current sensitive for single mode operation, widely-spaced dual mode operation, and narrow-band multimode operation.