Group-index birefringence and loss measurements in silicon-on-insulator photonic wire waveguides

Group-index birefringence in silicon-on-insulator photonic wire waveguides is determined through a polarization beating technique and a Fabry-Pérot resonance method. A large group-index birefringence, up to 0.67, is obtained as a result of the structural asymmetry and high field confinement of our waveguides. The group index and linear propagation loss are also determined. In particular, the group index is found to be as large as 4.45 due to the significant change in the effective mode index of the waveguide as a function of the wavelength. The effects of structure size on the measured losses and group indices are analyzed. Our experimental results are in good agreement with our simulations, and the method employed is found to be effective in analyzing the linear properties of submicrometer optical waveguide structures.