Optical bistability and optical switching in semiconductor lasers with varying bias current

Abstract

Optical bistability and optical switching in semiconductor lasers with light injection by varying bias current are predicted. They arise from the gain and refractive index change in the laser active region. When the lasing frequency of the external field is fixed, there is a lowest power for the external light to realise the optical bistability. And a larger current loop can be formed for a larger injected light power. When the optical power of the external signal is fixed, there is a range of the frequency detuning between the laser and the external field to realise the bistability. The switching-off current and the switching-on current for the optical hysteresis loop are dependent on the parameters of the external light (the power and the frequency) and are related to the laser parameters. Both the switching-on and the switching-off time of the optical switch can be reduced by applying a large amplitude of electrical pulse. However, a larger injected light power or a smaller frequency detuning results in a shorter switching-on time and a longer switching-off time. A small detuning is desired to reduce the overall switching time and the overall switching time has a minimum at a certain value of injected light power.