Mode switching of Fabry-Perot laser diodes

Mode switching of a Fabry-Perot laser diode with low spontaneous input is analyzed. To understand the transients, an additional mode competition is required. This enhanced mode competition is analyzed. Its model is based on standing waves of longitudinal laser modes burning in a spatial carrier corrugation which modulates the gain. Internal reflections by the gain corrugations always fulfil the resonance condition at the wavelength of the mirror resonances. In this way, each laser mode decreases its own losses slightly with increased photon density. As a result the total gain (inclusive of all losses) of the dominant laser mode is increased to a value >0 during nearly the entire switching process. Therefore, the photon density can increase exponentially with a risetime of about 1 ns