A broadly tunable femtosecond optical parametric oscillator (OPO) based on KTiOPO4 that is externally pumped by a self-mode-locked Ti:sapphire laser is described. Continuous tuning is demonstrated from 1.22 to 1.37 μm in the signal branch and from 1.82 to 2.15 μm in the idler branch by using one set of OPO optics. The potential tuning range of the OPO is from 1.0 to 2.75 μm and requires three sets of mirrors and two crystals. Without prisms in the OPO cavity, 340 mW (475 mW) of chirped-pulse power is generated in the signal (idler) branch for 2.5 W of pump power. The total conversion efficiency as measured by the pump depletion is 55%. With prisms in the cavity, pulses of 135 fs are generated, which can be shortened to 75 fs by increasing the output coupling.
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