Ultralow-threshold Kerr-lens mode-locked Ti:Al_2O_3 laser

An ultralow-threshold Kerr-lens mode-locked $\mathrm{Ti}:{\mathrm{Al}}_2{\mathrm{O}}_3$ laser achieved by use of an extended cavity design is demonstrated. Mode-locking thresholds as low as 156 mW are achieved. Pulses with durations as short as 14 fs and bandwidths of $>100 \mathrm{nm}$ with output powers of $\sim 15 \mathrm{mW}$ at 50-MHz repetition rates are generated by only 200 mW of pump power. Reducing the pump power requirements to a factor of $10\times$ less than required by most conventional Kerr-lens mode-locked lasers permits inexpensive, low-power pump lasers to be used. This will facilitate the development of low-cost, high-performance femtosecond $\mathrm{Ti}:{\mathrm{Al}}_2{\mathrm{O}}_3$ laser technology.