Birefringence suppression of UV-induced refractive index with grooves in silica-based planar lightwave circuits

An effective method for suppressing the birefringence of a UV-induced refractive index change is demonstrated for phase trimming of waveguides in planar lightwave circuits. By employing grooves on both sides of the waveguide to control the UV-induced strain, a significant reduction is achieved from 1.46×10^-4 to 0.11×10^-4 in the UV-induced birefringence for a π phase shift averaged between the TE and TM modes in a 2 mm-long waveguide.