Passive mode-locking in semiconductor lasers with saturable absorbers bandgap shifted through quantum well intermixing

Abstract

Passive mode-locking in semiconductor lasers in a Fabry-Perot configuration with a bandgap blueshift applied to the saturable absorber (SA) section has been experimentally characterized. For the first time a fully post-growth technique, quantum well intermixing, was adopted to modify the material bandgap in the SA section. The measurements showed not only an expected narrowing of the pulse width but also a significant expansion of the range of bias conditions generating a stable train of optical pulses. Moreover, the pulses from lasers with bandgap shifted absorbers presented reduced chirp and increased peak power with respect to the nonshifted case.

Ultrafast pulse generation in semiconductor lasers

“…Alternatively, post-fabrication modification of the saturable absorber band-edge through intermixing techniques [8], modifies the laser emission wavelength and hence operating regime as a function of injection conditions. This method although less spectrally selective than using intra-cavity filters maintains the broad laser bandwidth and sub-ps pulse durations.…”