High-order mode suppression in an integrated optical thin-film lithium niobate phase modulator

Subject of study. The subject of this study was the differential modal damping and filtering of the fundamental mode in channel optical waveguides fabricated through the etching of a lithium niobate thin film on a silicon dioxide buffer layer. Aim of study. This study aimed to develop a method for high-order mode suppression in multimode channel waveguides based on thin-film lithium niobate and determine the topology of a highly efficient integrated optical phase modulator based on thin-film lithium niobate, fabricated using contact photolithography. Method. The numerical simulation and experimental investigation of the optical and electro-optical properties of an integrated optical modulator were conducted. Main results. For an integrated optical phase modulator based on a channel waveguide produced by etching thin-film lithium niobate, the influence of planar electrodes on the differential damping of high-order modes is analyzed, and the conditions for the quasi-single-mode light propagation are determined. The topology of an integrated optical phase modulator is proposed, for which the effective suppression of high-order modes and the high efficiency of electro-optical modulation are experimentally demonstrated. The achieved parameter of modulation efficiency U pi L approximate to 4 V cm is four times lower than that of commercially available integrated optical phase modulators based on bulk lithium niobate. Practical significance. Approaches to solving the problem of the fast and inexpensive production of integrated optical modulators based on thin-film lithium niobate using standard contact photolithography, which has significant limitations in resolution and alignment accuracy, are shown. (c) 2024 Optica Publishing Group