Modal birefringence-free lithium niobate waveguides

Abstract

We investigate polarization-insensitive waveguide designs afforded by the interplay of material and waveguide birefringence in LiNbO₃-on-insulator photonic wires. Fundamental mode birefringence-free operation in the 0.8-1.8 μm spectral range is predicted for a suitable choice of waveguide widths in the 375-600 nm range. Optimized buried waveguide designs yield broadband (1350-1625 nm) index matching between TE₀₀ and TM₀₀ modes. Furthermore, simultaneous phase- and group-velocity matching at infrared wavelengths appears feasible for pulse durations as short as 100 fs.