Advances in Mid-infrared Nanosecond OPOs Directly Pumped by Tm 3+ -doped and Tm 3+ ,Ho 3+ -codoped Fiber Lasers

Recent work on Tm3+-doped and Tm3+,Ho3+-codoped 2 µm fiber lasers and efficient pumping of mid-infrared nanosecond OPOs based on ZnGeP2 or OP-GaAs non-linear crystals with watt-level output power is presented.