Comb generation bandwidth for frequency-shifted feedback semiconductor lasers

An analytical expression is obtained for the comb frequency bandwidth in frequency-shifted feedback (FSF) semiconductor lasers. In contrast to previous theoretical predictions, it is found that the achievable bandwidth and a figure of merit, defined for maximizing the product of the bandwidth and output power for the FSF laser, are mainly determined by the spectral width of the gain. It is thus expected that semiconductor lasers, with their high net gain and ease of operation, will offer significant advantages over other laser systems for the application of FSF.