Abstract
In this research, a vertical silicon nitride strip-loaded grating coupler on lithium niobate thin film was proposed, designed, and simulated. In order to improve the coupling efficiency and bandwidth, the parameters such as the SiO2 cladding layer thickness, grating period, duty cycle, fiber position, and fiber angle were optimized and analyzed. The alignment tolerances of the grating coupler parameters were also calculated. The maximum coupling efficiency and the −3 dB bandwidth were optimized to 33.5% and 113 nm, respectively. In addition, the grating coupler exhibited a high alignment tolerance.
Highlights
The emergence of lithium niobate on an insulator (LNOI) has greatly promoted the development and progress of integrated optics devices [1,2]
Due to its extraordinary nonlinearity and excellent electrooptical properties, LNOI can be used in a variety of expandable on-chip devices to provide nonlinear wavelength conversion and high-speed optical modulation [7,8,9]
Various photonic devices have been reported in Si3N4 strip-loaded LNOI, including a multiplexer [15], a micro-ring resonator [16], and an electrooptic modulator [17]
Summary
The emergence of lithium niobate on an insulator (LNOI) has greatly promoted the development and progress of integrated optics devices [1,2]. It is very important to improve the coupling efficiency between an LNOI waveguide and fiber. A grating coupler is an effective way to solve the coupling problem between an LNOI waveguide and optical fiber [10,11,12].
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