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Athermal silica-based interferometer-type planar light-wave circuits were realized by a newly developed multicore fabrication method. In this method, inductively coupled chemical-vapor deposition and polishing technologies are adopted on a silica substrate with a trench-type waveguide pattern prepared by reactive ion etching. Two kinds of deposited core material, 10GeO2-90SiO2 (mol. %) and 8GeO2-5B2O3-87SiO2 (mol. %), which show wavelength temperature dependence of 9.7 and 8.1 pm/degree C, respectively, were used to prepare the waveguide sections in a device. By adjustment of the lengths of waveguide sections with these two different core materials, athermal characteristics of less than 0.5 pm/degree C were achieved for Mach-Zehnder interferometer filter devices at the 1.55-microm wavelength range while the temperature varied from -20 to 80 degrees C. The new method is also applicable for the preparation of many other kinds of functional devices.

Low-propagation-loss Ge–B–SiO2 planar waveguides have been achieved by inductively coupled plasma-enhanced chemical vapor deposition. The significant effects due to annealing temperature, hydrogen loading, and KrF excimer ultraviolet laser irradiation on the optical properties of Ge–B–SiO2 films have been investigated. A temperature-insensitive Mach–Zehnder interferometer-like optical filter has been demonstrated by means of a double-core fabrication method using 10GeO2–90SiO2 (10G90S) and 8GeO2–5B2O3–87SiO2 (8G5B87S) as two different waveguide cores. We have achieved less than 0.5 pm/°C temperature dependence of the central wavelength of the filter at 1550 nm while varying the temperature from −20 to 80 °C.

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