Precise and Robust Domain Engineering Based on Faraday Cage Effect for Thin-film Lithium Niobate Photonics

TL;DR

This paper introduces a nanoscale Faraday cage technique for precise, robust domain engineering in thin-film lithium niobate photonics, significantly improving efficiency and scalability of nonlinear optical devices.

Contribution

The authors develop a novel Faraday cage-based method for controlling polarity in TFLN waveguides, enabling high-precision, scalable fabrication without real-time monitoring.

Findings

Achieved a normalized SHG efficiency of 6242 %W-1cm-2.

Demonstrated improved precision and robustness over traditional methods.

Enabled scalable fabrication of nonlinear photonic circuits.

Abstract

Thin-film lithium niobate (TFLN) waveguides are promising for efficient second-harmonic generation (SHG) owing to their strong optical confinement and large second-order nonlinearity. However, robust fabrication of high-efficiency devices remains challenging, as existing domain engineering methods lack precise and robust controls of polarity distributions. Here, we propose and demonstrate a domain engineering technique that utilizes nanoscale Faraday cages to shape the electric-field distributions during poling, physically defining polarity distribution by the geometry of the Faraday cages without real-time monitoring. As a proof of concept, the method is used to fabricate a spatially selectively poled TFLN waveguide, where all regions are poled except for a 400-nm-wide central. This waveguide achieves a normalized SHG efficiency of 6242 %W-1cm-2. Systematic investigation of the inverted domain growth dynamics confirms the enhanced precision and robustness of this approach over conventional time-controlled methods, paving the way for scalable nonlinear photonic circuits.