UV-Transferred Ultrasmooth Flexible Interfaces for a Multi-Functional Terahertz Metagrating with Passive Switching and High-Sensitivity Mechanical Tuning

Terahertz (THz) filters are pivotal for sensing and imaging, yet their performance on flexible substrates is often hindered by scattering losses from rough metal–polymer interfaces. This work introduces a UV-release tape (UV-RT) assisted transfer strategy that directly addresses this challenge by enabling the lossless transfer of metallic metagratings from silicon to a flexible polymer, thereby preserving an atomically smooth functional interface with a roughness of Rq ≈ 0.245 nm. This ultrasmooth surface is fundamental to the demonstrated high-performance flexible device, which combines multiple device-level functionalities on a single platform, including passive switching between bandpass and bandstop filtering via geometric design, distinct polarization-selective resonances, and active mechanical frequency tuning with a high sensitivity of 18.65 GHz %–1. By providing a versatile transfer route to atomically flat, terahertz photonics with well-defined and stable resonant characteristics, the UV-RT method supports flexible terahertz photonic structures for resonance-based filtering and tuning.