Waveguide crossing characterization for silica planar lightwave circuits

Optical waveguide crossings based on silica-on-silicon technology are investigated. The effect of crossing angle (θ) on light transmitted at through and cross-port on a sequence of waveguide crossings with angle varying from 7 to 28° is modeled and experimentally validated. Results demonstrate that structures with small footprint (θ≈9°) can achieve low crosstalk of -32 dB with high throughput, insensitivity to wavelength of operation, low polarization dependent loss of 0.6 dB, and low sensitivity to fabrication tolerances. As a result, waveguide crossings with small crossing angle present an attractive approach to reducing the overall component footprint without compromising the performance.