Silicon-Dioxide Waveguides With Low Birefringence

We describe the use of highly boron-doped silicon dioxide for the preparation of optical waveguides with very low birefringence. Plasma-enhanced chemical vapor deposition was used to vary the boron content from 5 wt% to 10 wt%, at a constant phosphorus content of 4.8%. A transition from compressive to tensile stress was observed at a boron concentration of 9.1%. Pedestal-type waveguides formed with the high-boron top cladding layer show low loss of 0.02 dB/cm. Arrayed waveguide grating devices with a polarization-dependent wavelength shift of 0.01 nm and excellent stability have been demonstrated.