High‐Performance Mode‐Multiplexing Device with Anisotropic Lithium‐Niobate‐on‐Insulator Waveguides

Abstract

Thin-film lithium-niobate photonics has attracted intensive attention due to its superior material properties. In particular, multimode lithium-niobate photonics is becoming attractive for the applications of high-capacity optical interconnects and high-efficiency nonlinear optics. However, multimode manipulation in lithium-niobate-on-insulator (LNOI) waveguides is not easy because there might occur some mode hybridness due to the vertical asymmetry as well as the material anisotropy. In this paper, high-performance mode-multiplexing devices with anisotropic LNOI waveguides are proposed, consisting of a multi-channel mode (de)multiplexer and a sharp multimode waveguide bend (MWB). The mode (de)multiplexer is designed with Z-propagation LNOI waveguides to avoid the mode hybridness. Meanwhile, the sharp MWB is designed to connect with a Y-propagation waveguide, enabling access to the highest electro-optic coefficient and second-order nonlinear coefficient. The fabricated mode (de)multiplexer has a low excess loss less than 0.2 dB as well as low crosstalk less than -19 dB in the wavelength range of 1520-1600 nm. These high-performance multimode photonic devices are useful for developing multimode LN photonics.

Four-Channel Broadband Mode (De)multiplexer Based on Thin-Film Lithium Niobate Platform

“…Thanks to the compatibility with mature complementary metal oxide semiconductor fabrication processes, several ADC-based structures have been proposed and experimentally verified on silicon-on-insulator platforms, including ultra-multi-channel and ultra-compact MMUXs/DEMMUXs. However, there are limited reports about MMUXs/DEMMUXs on the lithium-niobate-on-insulator (LNOI) platform so far. − …”

Demonstration of a High‐Performance 3 dB Power Splitter in Silicon Nitride Loaded Lithium Niobate on Insulator

“…[ 11,12 ] Among these different platforms, LNOI has been widely studied by academic and industrial communities because of its wide transparency window, low loss, strong electro‐optic (EO) coefficient, and relatively high refractive index difference compared to silicon dioxide cladding (Δn ≈ 0.7 at λ = 1550 nm). [ 13 ] So far, there are various high‐performance photonic devices based on the lithium niobate (LN) platform have been reported, such as lasers, [ 14 ] electro‐optical modulators, [ 15 ] mode (de)multiplexers [ 16 ] and grating couplers. [ 17 ] Nevertheless, further expansion of the passive component toolbox is required to realize monolithic photoelectric integrated circuits with active components.…”