Generation of fast-tunable femtosecond visible radiation via intra-cavity sum-frequency in a high-power ultra-broadband NIR NOPO

High repetition rate femtosecond VIS radiation is normally generated in optical parametric oscillators (OPOs) either by generating VIS light via intra-cavity SHG or SFG [1, 2] or in VIS OPOs employing Ti:sa as a pump laser [3, 4]. Recently we demonstrated an efficient intra-cavity SFG in a non-collinear OPO (NOPO) pumped by thin disk oscillator [5]. Here, we present a NOPO system, pumped by the high power fiber laser, that is capable to deliver simultaneously intrinsically synchronized NIR and VIS femtosecond pulses which are widely tunable, scalable in power and do not require any realignment during the tuning process, therefore offering a possibility of a high tuning speed. The system is based on the unique properties of the NIR NOPO [6], which delivers high power femtosecond widely tunable radiation in a range of 640–1000 with a cavity length adjustment as a tuning mechanism. By introducing a second focus for intra-cavity sum-frequency generation (SFG) of the oscillator light with the residual from SHG fundamental pump light, visible radiation tunable in a range of 396–500 nm with output power up to 1.6W was generated.