Intracavity spectral shaping and chirp tailoring for high power ultrashort pulse generation from hybrid modelocked external cavity semiconductor lasers

Summary form only given. We demonstrate the potential for artificially tailoring the chirp of output optical pulses. The chirping mechanism of the modelocked semiconductor laser is primarily due to intracavity gain dynamics. Self phase modulation (SPM) in the gain medium, related to gain depletion, imposes a parabolic chirp on the optical pulse. It is well known for dye saturable absorbers that the sign of chirp depends upon whether the interaction takes place above or below the resonance frequency. A similar effect can be expected for SPM of semiconductor optical amplifiers (SOA). Since the linewidth enhancement factor of the SOA has different values depending on the optical frequency, the sign and the amount of chirp generated by the SOA can be tailored by controlling the position and shape of the intracavity pulse spectrum. Experimentally, this is achieved using intracavity spectral shaping techniques. The signs of the chirp were confirmed by measuring the amount of group delay dispersion of a dual grating dispersion compensator for optimum pulse compression.