Recovery dynamics of a PbS quantum dot doped glass passive mode locker

Summary form only given. Recently we demonstrated that PbS quantum dot doped glasses, fabricated by thermal treatment of an oxide molten glass, can be used as intracavity saturable absorbers to obtain self-starting mode locking in infrared solid-state lasers. In particular, using these absorbers in a Cr:forsterite laser we obtained pulses as short as 4.6 ps with a time-bandwidth product of 0.35 and pulse energies up to 1 nJ. Because of the large exciton Bohr radius (18 nm) and the small band gap energy (0.4 meV at RT) these saturable absorbers are suitable for operation over a wide spectral rang from visible to 3 /spl mu/m. However, it was unclear why shorter pulses then 4.6 ps could not be obtained. Here we perform degenerate pump-probe experiments to address this point and determine the recovery time of the optical nonlinearity.