Fabrication and characterization of continuous wave direct UV (λ=244nm) written channel waveguides in chalcogenide (Ga:La:S) glass

Mairaj, A.K., Hua, P., Rutt, H.N. and Hewak, D.W. (2002) Fabrication and characterization of continuous wave direct UV (λ=244nm) written channel waveguides in chalcogenide (Ga:La:S) glass. IEEE Journal of Lightwave Technology, 20 (8), 1578-1584. (doi:10.1109/JLT.2002.800266).

Abstract

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 non-linear 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 to 90 kW/cm²) and scan velocities ( Vscan = 0.005 to 0.067 m/s). The exposed regions were evaluated through atomic force microscopy (AFM) and surface compaction (0.3 - 3.6µm) 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 1.3µm with a positive change in refractive index (Δn = 10^-3). The chemical mechanism for these photoinduced changes with resulting photodensification has been correlated with a relative increase in the lanthanum content within the waveguide core.

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Contributors

Author: D.W. Hewak

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