Bistable operation and spectral tuning of injection laser with external dispersive cavity

Spectral tuning of an AlGaAs-GaAs laser with external dispersive cavity, operating in a singlefrequency regime, has been studied. The dependence of output power on wavelength was shown to have the shape of a hysteresis loop, which indicates the existence of bistable operation. Such a behaviour in a laser is due to the existence of a composite cavity comprised of a laser-diode intrinsic cavity and an external dispersive cavity. The refractive index of a semiconductor medium depends on the inversion population, and, since the inversion population depends on the radiation intensity this causes optical nonlinearity of the active diode region. As a result, such an optical laser scheme becomes analogous to the well known optical bistable systems, including a Fabry-Perot interferometer with optical nonlinearity.