UV photosensitivity in a Ta2O5 rib waveguide Mach-Zehnder interferometer

The ultraviolet (UV) photosensitivity of Ta
₂
O
₅
measured in a rib waveguide Mach-Zehnder interferometer (MZI) is reported. With a cumulative fluence of 72 J/cm
²
at a wavelength of 248 nm incident upon one arm through a 3-mm-long window, the MZI exhibits a phase shift of 8/spl pi/ radians at wavelength /spl lambda/=1.55 μm, corresponding to a saturated refractive index change of 2.1×10/sup -3/. Real time measurements of the MZI output during exposure are given and the UV-induced refractive index change is found to be negative.