Abstract

Lithium niobate (LiNbO₃, LN) is widely used for photonic applications, thanks to its wide transparency range, electro-optic and nonlinear optical properties [1]. Recently available lithium-niobate-on-insulator (LNOI) substrates afford high index contrast and thus tight field confinement in LN photonic devices such as optical modulators and microring resonators [2, 3]. However, similar to other (e.g. SOI) platforms, high-confinement waveguides are strongly birefringent, which leads to e.g. polarization mode dispersion with deleterious effects for delay-based filters, modulators and other signal processing and transmission devices [4]. Here, with vectorial simulations for high-confinement ridge waveguides in LNOI, we show how the interplay of the high birefringence of LN and of the waveguide structure can be employed to achieve birefringence-free designs in a broad spectral range, from 0.8 up to 1.8 μm, through a careful tuning of the LNOI ridge dimensions.

© 2017 IEEE