Light-to-light transducers with amplification

A device considered as a light-to-light transducer with amplification has been proposed and fabricated. The device structure is direct and has vertical (but offset) integration of a heterojunction phototransistor onto a cladding layer of a double-heterojunction light-emitting diode on one side of a substrate. Light amplification becomes possible by combining a transistor function and a light-emitting function. A gain of 15 times has been measured against an input-light-power of 10 μW at 1.15-μm wavelength, at a bias voltage of 4.25 V, and with a load resistance of 5 Ω. With the utilization of the Early effect in the weak-input-power range and the suppression of a regenerative effect in the intermediate-power range, an amplification characteristic close to the linear relation has been realized, for the first time, for an input light power from 0 to 20 μW, at a bias voltage of 4.0 V and with a load resistance of 5 Ω