NEAR-UNITY QUANTUM EFFICIENCY OF ALGAAS/GAAS QUANTUM-WELL INFRARED DETECTORS USING A WAVE-GUIDE WITH A DOUBLY PERIODIC GRATING COUPLER

Quantum well infrared detectors based on a waveguide with a doubly periodic grating coupler are shown to provide quantum efficiencies of nearly unity with respect to unpolarized polarization. This is a factor of six larger than for a conventional 45-degrees polished edge detector with the same quantum well characteristics. As a further advantage the detector response becomes nearly insensitive to the polarization direction of the incident radiation. Detectors have been fabricated and tested. Measurements lead to a maximum quantum efficiency of 92% with respect to unpolarized radiation, with a response linewidth = 0.8-mu-m, thus confirming theory.