Bandwidth and beam quality of barium borate parametric oscillator synchronously pumped by an active-passive modelocked Nd:YAG laser

We report on the generation of tunable pulses in the near IR through a BBO parametric oscillator pumped by the second harmonic of a conventional active-passive modelocked Nd:YAG laser. Different arrangements will be compared. Without spectral selective elements peak pump conversions of 75% are observed. With a grating, we show that it is possible to achieve frequency widths of the IR pulses comparable to those of the pump itself. The factor M2, through which we characterize the spatial quality of the beam, is 1.7 just above threshold, and it does not exceed 2.5 even when the depletion of the pump pulses is larger than 30%.