Abstract: A high-speed, light emitting device which utilizes a solid state source for generating light for use in fiber optical communications. The source is an active, narrow band gap layer of semiconductive material between heterojunctions formed with a p.sup.+ -type material on one side of an n.sup.+ -type material on the other side. A mirror on the back of the source reflects light toward an optical fiber abutting the substrate on the front of the source. A side mirror traverses the edge of the active layer at an angle of about 45.degree. and reflects light traveling parallel to the active layer toward the optical fiber. Contacts are coupled to the semiconductor material for applying an electrical signal across the active layer to generate light. In a preferred embodiment, the active layer is GaAsSb joined to GaAlAsSb and the substrate is GaAs.

Abstract: A preamp for coupling to an avalanche photodiode (APD) of an optical receiver has an input stage including a dual gate field effect transistor (FET) and a single gate FET coupled in a cascade arrangement. The dual gate FET has its first gate coupled to the output of the APD, its second gate and source grounded, and its drain driving the gate of the single gate FET in a cascade arrangement. The source of the single gate FET is level-shifted and coupled by means of a feedback resistor to the first gate of the dual gate FET to provide a negative feedback. The output stage is a third FET with its gate coupled through a blocking capacitor to the source of the single gate FET in the input stage and with its drain providing the output of the preamp. In a preferred embodiment, the FETs used are GaAs FETs (GAASFETs).

Abstract: An inverted heterojunction photodiode for use as a laser detector sensitive to the 8 - 14 .mu.m portion of the infrared spectrum and operable above 77.degree. K. The diode structure comprises a PbTe substrate, a first buffer layer of a Pb.sub..90 Sn.sub..10 Te material on said substrate and a second active layer of a Pb.sub..80 Sn.sub..20 Te material on said buffer layer. The first and second layers are grown by liquid phase epitaxy.