Numerical Study of the Influence of the Microtrenches on Optical Properties of Integrated Optical Waveguides on Lithium Niobate on Insulator

Mode composition was simulated to find the waveguide cross section parameters for single mode propagation in wide wavelength range from 1.5um to 1.6um for both mode polarizations. The anisotropy of X-cut thin film lithium niobate was considered during simulations for Y-propagation of radiation in the waveguide. Numerical study was performed for the influence of microtrenches formed by the reactive ion etching in inductively coupled plasma (ICP/RIE) process on optical parameters of the fundamental mode in a shallow etched waveguide on lithium niobate on insulator. It was shown that microtrenches influence effective indices of waveguide modes. TE-mode effective index change is close to refractive index contrast in proton exchange waveguides on lithium niobate. Influence of microtrenches on optical bent losses was also investigated. Increasing the degree of light confinement in waveguide with microtrenches was observed and, as a result, a decrease in optical losses at critical bent radius was observed. Results of current work showed the need to consider microtrenches appearing in dry etching process in the waveguide design.