OPTICAL SWITCHES AND DETECTORS UTILIZING INDIRECT NARROW-GAP SUPERLATTICES AS THE OPTICAL MATERIAL

摘要

The present invention relates to novel optical devices operating in the infrared, based on indirect narrow-gap superlattices (INGS) as the active optical materials. The novel optical devices include (1) wideband all-optical switches, which combine small insertion loss at low light intensities with efficient optical switching and optical limiting at high intensities, and (2) wideband infrared detectors with high collection efficiency and low tunneling noise currents, suitable for use in longwave infrared focal plane arrays. INGS comprise multiple semimetal/semiconductor layers having compatible crystal symmetry across each heterojunction between a given semimetal and the adjoining semiconductor, wherein each semimetal layer sandwiched between semiconductor layers is grown thin enough that each semimetal layer becomes a semiconductor, and wherein each semiconductor layer is thin enough that there is coupling between adjacent semiconductor layers. The present invention utilizes INGS, which are fabricated to meet the criteria E.sub.g.sup.ind h&ohgr; E.sub.g.sup.dir, especially where h&ohgr; 100 meV, as the optical material for optical switches. The present invention also utilizes INGS as optical detectors if they are fabricated such that E.sub.g.sup.ind E.sub.g.sup.dir h. omega., especially where h&ohgr; is less than 155 meV.