A realistic model for actively modelocked semiconductor lasers

Experiments show that pulses generated by a semiconductor laser modelocked with a frequency limiting element are often not transform limited, indicating the existence of a frequency chirp. A model is developed to calculate the experimentally observed quantities such as the frequency spectrum and the temporal autocorrelation function both before and after pulse compression. The model indicates that the gain nonlinearity plays a crucial role in determining the rate of frequency chirp in the pulse. Good agreement with our experimental data for a single quantum well laser is obtained when the gain nonlinearity is set to /spl isin//sub s/=7/spl times/10/sup /spl minus/23/ m/sup 3/.>