Laser-trimming adjustment of waveguide birefringence in optical FDMcomponents

Laser trimming of amorphous-silicon stress-applying films deposited on silica-based single-mode waveguides is demonstrated for controlling waveguide birefringence. Successful applications to polarization-insensitive operation of an optical ring resonator and a Mach-Zehnder interferometer are presented. A phase difference of less than π/100 between TE and TM modes has been attained. It is noted that this laser trimming method can also be applicable to other material devices such as LiNbO₃ and yttrium-aluminum-garnet (YAG), where waveguide birefringence control is a crucial factor in achieving the practical performance of the device