Greater than 20%-efficient frequency doubling of 1532-nm nanosecond pulses in quasi-phase-matched germanosilicate optical fibers.

We fabricated second-order nonlinear gratings in D-shaped germanosilicate fibers, using thermal poling and periodic electrodes defined by standard photolithography. These gratings, which are up to 75 mm long, were used for efficient quasi-phase-matched frequency doubling of 1.532-mum nanosecond pulses from a high-power erbium-doped fiber amplifier. Average second-harmonic powers as high as 6.8 mW and peak powers greater than 1.2 kW at 766 nm were generated, with average and peak conversion efficiencies as high as 21% and 30%, respectively.

Experimental evidence of differences in the absorption spectra of clustered and isolated ions in erbium-doped fibers.

The absorption spectra of clustered and isolated ions in erbium-doped germanosilicate fibers have been experimentally studied. The ground-state absorption spectra broaden as the degree of erbium-ion clustering increases, indicating that the absorption spectrum of clustered ions is significantly different from that of the homogeneous ions. This fact is confirmed by comparison of the broadened absorption spectra with the fiber's unbleachable loss spectrum, a direct measurement of the clustered ions. This is the first experimental evidence to the authors' knowledge that indicates different absorption cross sections for the two species of ions in germanosilicate glass, an assumption that is used in the theoretical description of self-pulsing in erbium-doped fiber lasers but is in direct contradiction to the pair-induced quenching model widely used to characterize erbium-doped fiber amplifiers.

Suppression of self-pulsing behavior in erbium-doped fiber lasers with resonant pumping: experimental results.

Experimental results are presented showing that resonant pumping can significantly improve the stability of erbium-doped fiber lasers. In particular, it is observed that an erbium fiber laser that exhibits sustained spiking behavior when pumped at 980 nm will revert to stable cw operation when pumped at 1510 nm.

Channel waveguide laser at 1 microm in Yb-indiffused LiNbO(3).

We report laser action in a Ti-diffused LiNbO(3) waveguide doped with trivalent Yb ions by thermal indiffusion. Lasing was observed at 1008, 1030, and 1060 nm with thresholds as low as 15-mW launched pump power. We reduced photorefractivity, which initially permitted only intermittent lasing, by annealing the sample in wet O(2). The annealed sample lased continuously in a cavity formed by high-ref lectivity mirrors; however, with a 7% output coupler the output power exhibited instabilities. The greatest value of the output power observed under these conditions was consistent with a slope efficiency of ~16% with respect to absorbed power.