Effect of wavelength shift on PLC-type WDM directional coupler by UV irradiation

The UV light of KrF excimer laser, which is used for making fiber gratings, is irradiated on PLC-type WDM directional couplers. After the irradiation, the shift of transmission wavelengths is observed as a function of UV exposure dose. The amount of the effective refractive index change of rectangular silica waveguides is calculated by the coupled mode theory and the measured data.