Inverse-Designed Lithium Niobate Nanophotonics

Abstract

Lithium niobate-on-insulator (LNOI) is an emerging photonic platform that exhibits favorable material properties (such as low optical loss, strong nonlinearities, and stability) and enables large-scale integration with stronger optical confinement, showing promise for future optical networks, quantum processors, and nonlinear optical systems. However, while photonics engineering has entered the era of automated “inverse design” via optimization in recent years, the design of LNOI integrated photonic devices still mostly relies on intuitive models and inefficient parameter sweeps, limiting the accessible parameter space, performance, and functionality. Here, we implement a 3D gradient-based inverse-design model tailored for topology optimization based on the LNOI platform, which not only could efficiently search a large parameter space, but also takes into account practical fabrication constraints, including minimum feature sizes and etched sidewall angles. We experimentally demonstrate a spatial-mode multiplexer, a waveguide crossing, and a compact waveguide bend, all with low insertion losses, tiny footprints, and excellent agreement between simulation and experimental results. The devices, together with the design methodology, represent a crucial step toward the variety of advanced device functionalities needed in future LNOI photonics and could provide compact and cost-effective solutions for future optical links, quantum technologies, and nonlinear optics.

Photon-pair generation using inverse-designed thin-film lithium niobate mode converters

“…It is worth noting the recent work on the topology optimization of linear TFLN photonic devices. 39 In comparison with this recent work, our approach uses shape optimization instead of topology optimization and leverages the inverse-design method in the context of nonlinear and quantum optics. In particular, our devices require a large etching depth of over 500 nm to satisfy the phasematching condition.…”

Broadband, Plasmon‐Modified SnSe2 Photodetector Based on LNOI Thin‐Film Platform

“…[ 6–9 ] By incorporating this thin‐film platform, optical limiting capabilities can be further enhanced. [ 10,11 ] Additionally, LiNbO 3 , as a multifunctional ferroelectric material, exhibits a strong spontaneous polarization effect. [ 12–14 ] This results in the generation and asymmetric distribution of surface charges, leading to the formation of “built‐in electric field” when exposed to light.…”

Inverse-designed silicon carbide quantum and nonlinear photonics

“…Primarily in silicon photonics 3 , there have been numerous experimental demonstrations of inverse-designed devices as well as system applications, such as particle accelerators 4 , optical ranging 5 , and communications 6 . Beyond silicon, inverse design has also been applied to other photonic platforms, including diamond 7 , silicon carbide 8 , lithium niobate 9 , and materials like chalcogenide glasses 10 . Nonetheless, inverse design for nonlinear photonics has been limited.…”