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Absorption and emission spectra, along with lifetime measurements, of Dy(3+) in Ge-Ga-S glasses are reported. Fluorescence is observed at 1.3, 1.8, and 2.9 microm. A Judd-Ofelt analysis is performed to determine branching ratios and quantum efficiencies. The hypersensitive transition (6)F(11/2) ? (6)H(15/2) at 1.3 microm has a quantum efficiency of 17%. Its suitability for an optical amplifier at 1.3 microm depends on the excited-state absorption from the (6)H(11/2) and (6)H(13/2) states, which has not yet been measured.

A single-mode Nd(3+)-doped tellurite glass fiber laser operating at 1.061 microm is described. We believe this is the first demonstration of a single-mode fiber laser in tellurite glass. A lasing threshold of 27 mW of 818-nm absorbed pump power and a slope efficiency output power versus pump power of 23% emitted from one end were observed in the fiber cavity with 11.9% Fresnel reflection at both ends.

Conventionally, large-mode-area (LMA) fiber lasers use free-space polarizing components to achieve linear polarization output. External components, however, significantly limit laser robustness and power scalability. We demonstrate, to the best of our knowledge, the first high-power all-fiber cavity single-polarization single-transverse-mode LMA fiber laser, without the use of free-space polarizing components. This has been achieved by using tightly coiled high-birefringence 20 microm core LMA fiber. The lasing spectrum at 1085 nm has been stabilized by a fiber grating, spliced at one end of a LMA fiber. Up to 405 W of single-polarization output with a polarization extinction of >19 dB with a narrow spectrum (1.9 nm FWHM) and in a single-transverse mode (M2 < 1.1) has been demonstrated. The simplicity of a monolithic-cavity approach is highly beneficial for a number of applications, including the use of a fiber laser for nonlinear wavelength conversion and for coherent and spectral beam combining.

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