Efficient frequency doubling at 776 nm in a ring cavity

Abstract

We report efficient frequency doubling (FD) at 776nm using periodically poled LiNbO3 (PPLN) in a ring cavity pumped by a commercial erbium-doped fiber amplifier (EDFA) operating at 1552nm. Two sets of input couplers are used that have been optimized to operate in the low pump and high pump regimes. The maximum conversion efficiencies measured for these couplers are 65.8% (transmittance T=4.5%) and 65.9% (T=9.1%). The internal conversion efficiencies are 85.0% and 88.2%, respectively, after the mode-matching efficiency and filtering transmittance have been taken into account. The maximum output powers obtained for the two couplers are 333mW and 602mW at pump powers of 535mW and 999mW, respectively. Coupling efficiency of more than 80% to single mode fibers indicates the high beam quality of the FD laser. This FD laser will be useful for quantum optics experiments in the telecommunications band and atomic physics experiments.