Temperature-independent optical filter at 1.55 µmwavelength using a silica-based athermal waveguide

The authors have realised a temperature-independent optical filter at a 1.55 µm wavelength, using a silica-based athermal waveguide in which optical path length is independent of temperature. The temperature coefficient of the central wavelength was successfully decreased to < 4 × 10-4 nm/K, which corresponds to 3% of that of conventional silica-based waveguide filters.