193  fs from an Yb:YAG oscillator mode-locked using nonlinear polarization rotation via Type I SHG with intrinsic...

The mode-locking technique using nonlinear polarization rotation via Type I second-harmonic generation (SHG) is demonstrated on the femtosecond timescale. The narrow spectral bandwidth of the loss modulation was broadened via a double crystal approach, which allows for mode-locking broadband gain media. We prove the predicted advantages of the technique to be correct utilizing intrinsic dispersion compensation and group-velocity mismatch management to produce 193 fs pulses. This eliminates the need for dispersion compensating elements. The technique can be applied to high-power lasers at any wavelength where a suitable SHG process is possible.