An InP-InGaAs Light Amplifying Optical Switch

Optical devices which perform logic functions and that can be cascaded, require optical gain. This mandates that the device contain an active element. We have designed such a device which we call a light amplifying optical swtich (LAOS). The gain is obtained from an NPN heterojunction bipolar phototransistor which is in series with a light emitting diode or laser. The first LAOS structure has been fabricated from lattice matched InGaAs on InP using gas source molecular beam epitaxy. A strained layer optical electrical absorber is sandwiched between the light emitter and the detector in order to reduce positive feedback and prevent latching. Analysis indicates that electrical gains of 3000 and optical gains as high as 100 can be obtained.