Radiation properties of channel waveguide discontinuities: a comparison of theoretical and experimental results

An orthonormal mode approach is presented for characterizing the radiation properties of waveguide discontinuities. The approach, which can be used to accurately estimate power loss and crosstalk in intersecting waveguides as well as polarization extinction in proton exchanged polarizers, requires only a knowledge of the optical mode profile, the operating wavelength, and the bulk substrate index. To demonstrate the validity of the technique, theoretical predictions for polarization extinction are compared to measured values for a proton exchanged polarizer fabricated on x-cut LiNbO3 and operated at 0.82 μm. Excellent agreement between theory and experiment is obtained for all polarizer lengths.