Highly efficient second-harmonic and sum-frequency generation of nanosecond pulses in a cascaded erbium-doped fiber periodically poled lithium niobate source

By combining erbium-doped fiber sources based on a large mode-area design and periodically poled lithium niobate, we have obtained single-pass conversion efficiencies of as much as 83% (energy efficiency) for second-harmonic generation into the near IR (768 nm) and of 34% for sum-frequency generation into the green (512 nm) for nanosecond pulses, using first-order quasi-phase matching. Pulse energies in excess of 80 mu J of second harmonic have been obtained from systems pumped by a single laser diode. (C) 1998 Optical Society of America. OCIS codes: 140.3500, 060.2410, 320.4240.