Temperature sensitivity of UV-induced Bragg gratings in silica-based waveguides on crystallized glass substrate

摘要

We have fabricated silica-based waveguide Bragg grating devices and have investigated temperature sensitivity of the Bragg wavelengths. Temperature sensitivity of Bragg wavelength is caused by temperature dependence of effective refractive index and thermal expansion. We examined boron-codoped germanosilicate glasses as waveguide materials in order to decrease a temperature sensitivity of refractive index. The boron-codoped germanosilicate films were fabricated by a plasma enhanced chemical vapor deposition. We adopted Si, silica, and crystallized glass as substrates in order to control the thermal expansion of the waveguides. Bragg grating with 0.53 μm period was formed by irradiation with a KrF excimer laser light through a phase mask. The Bragg wavelength shift of 9.7pm/°C was obtained in the B-Ge-SiO_2 core waveguide on a silica substrate, while the Bragg wavelength shift was 11pm/°C in the with Ge-SiO_2 core waveguide on a Si substrate, which was a conventional-type waveguide Bragg grating device. The Bragg wavelength shift was reduced to 7.8pm/°C by using B-Ge-SiO_2 core and a crystallized glass substrate with zero thermal expansion coefficient, which was 2/3 of the value of the conventional waveguide Bragg grating device.