Enhanced ultraviolet photosensitivity and lowered temperature-dependent performance of Ge-doped SiO2 planar waveguides with boron doping.

We have demonstrated a low temperature-dependent silica-based Mach-Zehnder interferometer-like optical filter on a pure silica substrate at 1.55 microm. 8GeO2-xB2O3-(92-x)SiO2 (x = 1, 2, 4 and 5 in mol.%) films have been deposited by inductively coupled plasma-enhanced chemical vapor deposition as the waveguide-core. Incorporation of the B2O3 into the waveguide-core has resulted in a lower temperature-dependent Mach-Zehnder interferometer-like optical filter wavelength from 9.4 to 8.1 pm/ degrees C at 1.55 microm. Furthermore, with a partial substitution of SiO2 by B2O3, the ultraviolet photosensitivity of the waveguide has significantly been improved. A low-propagation-loss of 0.11 dB/cm at 1.55 microm has been achieved by using actual Mach-Zehnder interferometer devices.