Recovery and switching missing longitudinal modes in a semiconductor laser

This investigation, for the first time, recovered and maintained a stable oscillation of every missing longitudinal mode in a hysteresis type mode-hopping gap of a Fabry-Perot semiconductor laser. The experimental method was to feedback the laser's beam with a polarization orthogonal to the laser's output polarization. An application of this technology was demonstrated, in which the laser's wavelength was switched among recovered modes with a speed that potentially could be up to several hundreds of megahertz. A special feature of this method is that both the laser power and spectral purity are preserved during mode recovery and mode switching.