Rapidly tunable femtosecond near-UV pulses from a non-collinear optical parametric oscillator

Broadband tunable femtosecond laser pulses are of great interest in numerous fields, such as spectroscopy or imaging. Here, we report on the generation of rapidly tunable radiation in the near UV by using intracavity non-collinear sum-frequency mixing between the visible pulses of a non-collinear optical parametric oscillator (NOPO) and a near-infrared beam. The NOPO is pumped by the third harmonic of an Yb-based master oscillator fiber amplifier (MOFA). For sum-frequency mixing, remaining fundamental pulses at 1030 nm are used. With this approach, near-UV pulses in a range of 333-413 nm with average output powers up to 90 mW and pulse durations from 158-240 fs are achieved. Fast tunability is demonstrated over the whole tuning range by varying just the cavity length. The system also allows for the generation of two simultaneous synchronized output pulse trains in the visible and the near-UV spectral range.