Power spectrum of a bistable external-cavity diode laser

A single-mode laser subject to weak optical feedback may become a multistable system. When the hopping rate becomes appreciable, the output power spectrum will be modified by the hopping. By applying a novel spectral theory of frequency jumps on a two-mode external-cavity semiconductor laser, we give an explicit analytical expression for the power spectrum that consists of four contributions, two of which are a weighted sum of individual quasi-mode spectra and two of which express the additional spectral broadening that is due to the jumping process.