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 pi /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 LiNbO/sub 3/ and yttrium-aluminum-garnet (YAG), where waveguide birefringence control is a crucial factor in achieving the practical performance of the device.>

A Mach-Zehnder (MZ) interferometer design is presented for application to wavelength-division multiplexed/frequency division multiplexed (WDM/FDM) systems. A variety of integrated-optic devices with low loss and low crosstalk, using silica-based waveguides, are demonstrated. MZ interferometers operate as multi/demultiplexers or frequency-selection switches. The channel spacing is determined by the waveguide arm length difference, and a spacing range of 1 GHz to 36 THz, corresponding to a wavelength spacing of 0.008-250 nm, is achieved. The devices for the WDM region have low fiber-to-fiber loss of 0.5 dB, and the devices for the FDM region have higher losses of 2-5 dB. Crosstalk of less than -15 dB was obtained for all the devices. A 5-GHz-spaced 16-channel frequency selection switch and a 10-GHz-spaced eight-channel multi/demultiplexer were also fabricated with a total loss of 5 dB and total crosstalk of -10 dB or less.>