Laser performance and spectroscopic analysis of optically written channel waveguides in neodymium-doped gallium lanthanum sulphide glass

We present a spectroscopic analysis and laser characterization of optically written waveguides in neodymium-doped gallium lanthanum sulphide (Nd³⁺-Ga:La:S) chalcogenide glass. Uniform channel waveguides were fabricated in Nd³⁺-Ga:La:S by exposure to radiation from a focused UV-laser beam (λ=244 nm), producing a refractive index change ▵n≈+10^-3. The observed laser performance and fluorescence decay were in good agreement with values calculated from a spectroscopic analysis of 85 μs for the ⁴F₃2/ lifetime and 5.9×10^-20 cm² for the emission cross section at 1075 nm. Low threshold laser operation with emission at 1075 nm and a slope efficiency of 17% is demonstrated. The active device is spatially single mode and exhibits up to 8.6 mW of output power and propagation losses of <0.5 dBcm^-1. Waveguide fabrication, photoinduced effects, and optical characterization in terms of spectroscopy, laser performance, and device attenuation are discussed.