Design and fabrication of gallium arsenide-aluminum gallium arsenide two-mode cross-coupled bistable laser diodes for optical switching and memory applications

Innovations in digital technology are fueling an explosive growth in services which provide information in digital format directly to the consumer. These new services are in turn spurring an unprecedented growth in transmission bandwidth requirements. Transmission of digital signals over optical fiber is expected to be a major part of this growth, but in order for this growth to be sustained, new all-optical switching systems must be developed to handle the higher bit rates of tomorrow's high-speed trunks. In particular, all-optical memory devices will be required for high bit-rate all-optical time-slot interchangers and fast packet switches. Because of cost considerations, these devices must be monolithically integrable into photonic integrated circuits (PICs). This work describes the development of a new type of optical memory element, the two-mode cross-coupled bistable laser diode (XCBLD). The operating characteristics of the XCBLD are studied theoretically using semiconductor laser rate equations, and working devices are fabricated in the GaAs/AlGaAs system and characterized experimentally. A fabrication process using temperature-controlled chemically-assisted ion beam etching (CAIBE) for the formation of low-loss etched mirrors and waveguides in (Al)GaAs is developed, which allows the XCBLD to be monolithically integrated with other passive and active components in complex PICs. This capability is then demonstrated by characterization of active and passive PIC elements using newly developed integrated test methods. In order to realize low-threshold cw operation of XCBLDs, a new type of semiconductor laser, the folded-cavity laser (FCL) is developed. The FCL uses etched turning mirrors to make a laser with a compact cavity and low threshold current. Successful cw operation of FCLs is reported. Finally, folded-cavity XCBLDs are fabricated and tested. Bistability and electrically-triggered latching is reported for devices operating at 77 K with pulsed current bias.