Carrier density depinning above threshold in semiconductor lasers: effects of carrier heating and spectral hole burning

Effects of carrier heating and spectral hole burning on the depinning of the carrier density above threshold in semiconductor lasers are theoretically investigated. The authors find that the magnitude of this depinning is proportional to the sum of the nonlinear gain coefficients due to injection heating, stimulated recombination heating, free carrier absorption heating, and spectral hole burning. The carrier heating, rather than spectral hole burning, is shown to be a dominant factor. Through the theoretical analysis, it is suggested that the comparison on the nonlinear gain coefficients measured from the small-signal modulation response and the spontaneous emission may provide an estimation on the value of the nonlinear gain coefficient due to injection heating and thus the carrier energy relaxation time in bulk semiconductor lasers