Ultrashort pulse reshaping using a semiconductor laser amplifier in a ring cavity

We describe an interferometric method for the reshaping and amplification of a mode‐locked train of short laser pulses, based on a ring cavity containing a semiconductor laser amplifier. The amplifying medium provides both the gain and the phase nonlinearity needed for pulse reshaping. Numerical simulations have shown that the best reshaping occurs with the use of a low finesse cavity operated at laser threshold. Upon these conditions, calculations have shown that both pulse compression and amplification are obtained over a broad range of values of the linear phase shift between the cavity and pulse train. Pulse amplification and compression factors exceeding 50 and 100, respectively, resulting in peak power amplification factors up to 1000, are predicted for a 25 dB amplifier. These factors can be increased by decreasing the ratio of the input pulse energy over the saturation energy of the amplifier.