Mode-locked Cr:LiSAF laser far off the gain peak: tunable sub-200-fs pulses near 1  µm

Abstract

We report, to the best of our knowledge, first mode-locking results of a Cr:LiSAF laser near 1 micrometer region. The system is pumped only by a single 1.1 W high-brightness tapered diode laser at 675 nm. A semiconductor saturable absorber mirror (SESAM) with a modulation depth of 1.5% and non-saturable losses below 0.5% was used for mode-locking. Once mode-locked, the Cr:LiSAF laser produced almost-transform-limited sub-200-fs pulses with up to 12.5 mW of average power at a repetition rate of 150 MHz. Using an intracavity birefringent filter, the central wavelength of the pulses could be smoothly tuned in the 1000-1020 nm range. Via careful dispersion optimization, pulsewidths could be reduced down to 110-fs level. The performance in this initial study was limited by the design parameters of the SESAM used, especially its passive losses, and could be improved with an optimized SESAM design.