Optical Bistability in Coupled-Cavity Semiconductor Lasers

Optical bistability is a rapidly expanding field of current research, and recent progress in this field1–3 has stimulated renewed interest in bistable semiconductors lasers4–22. Optical bistability in semiconductor lasers is an interesting subject because of their many advantages: they have optical gain, they can be controlled both electronically and optically, and they can be operated faster than nano- to sub-nanoseconds. In a commonly used scheme, inhomogeneous current injection along the laser cavity (using a segmented contact) is used, so that part of the cavity acts as a saturable absorber. This scheme is usually found to be limited in the current and temperature range for which bistability is observed. Moreover, since the “OFF” state in this case is below threshold, the turn-on delay will be limited by the spontaneous carrier lifetime leading to long delay times of several tens of nanoseconds; and since the “ON” state is by necessity close to threshold, the available output power is limited. An extensive review, including absorptive and dispersive bistability in semiconductor injection lasers, has been presented by Kawaguchi20.