Gallium lanthanum sulphide (Ga:La:S) optical glass is an interesting material for both fiber and planar technologies, as it offers possibilities for a wide array of devices suitable for use in both nonlinear applications and as IR lasers. Direct laser writing into this glass has yielded low-loss single-mode channel waveguides. Samples were exposed to above-bandgap illumination of focused UV (λ=244~nm) light at varying intensities (IUV = 1.5 -90~kW/cm2 ) and scan velocities (VSCAN = 0.005 -0.067~m/s). The exposed regions were evaluated through atomic force microscopy (AFM), and surface compaction (0.3-3.6 µm ) was observed. Sample topography was examined using a scanning electron microscope (SEM) with analysis of chemical changes within the exposed regions performed with energy-dispersive X-ray microscopy (EDAX). Waveguide attenuation was measured to be 0.2±0.1 dB/cm at 1.3 µm with a positive change in refractive index (Δn =10-3). The chemical mechanism for these photo-induced changes with resulting photodensification has been correlated with a relative increase in the lanthanum content within the waveguide core.
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