HIGHLY EFFICIENT 2ND-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 des ign and periodically poled lithium niobate, we have obtained single-pa ss conversion efficiencies of as much as 83% (energy efficiency) for s econd-harmonic generation into the near IR (768 nm) and of 34% for sum -frequency generation into the green (512 nm) for nanosecond pulses, u sing first-order quasi-phase matching. Pulse energies in excess of 80 mu J of second harmonic have been obtained from systems pumped by a si ngle laser diode. (C) 1998 Optical Society of America. OCIS codes: 140 .3500, 060.2410, 320.4240.