# Direct Photochemical Patterning of Lithium Niobate Structures for Scalable Nonlinear Optical Metasurfaces

## TL;DR

A new method for patterning lithium niobate at room temperature simplifies fabrication and enables scalable, cost-effective production of photonic devices.

## Contribution

A scalable ambient photochemical method for patterning lithium niobate without cleanrooms or harsh etching.

## Key findings

- The method produces LN metasurfaces with feature resolution down to 30 μm.
- Patterned structures show tunable isotropic second harmonic generation without phase matching.
- The technique can be extended to materials like barium titanate and lithium tantalate.

## Abstract

Lithium niobate (LN) is one of the most sought‐after materials for nanophotonic devices, including frequency converters, modulators, and quantum light sources. Integration of LN into optical devices, however, is hampered by significant top‐down fabrication challenges due to its exceptional chemical resistance. Scalable fabrication methods that preserve material quality while reducing fabrication complexity and cost are, therefore, crucial to advancing LN devices. A photochemical metal–organic decomposition technique is presented for the scalable patterning of LN at ambient conditions, eliminating the need for harsh etching conditions and cleanroom protocols. The method utilizes a solution of a custom‐prepared photosensitive organometallic precursor as a negative photoresist. The ultraviolet (UV) light exposure of the thin films of the precursor through a photomask, followed by rinsing with ethanol, yields amorphous patterns, which transform into crystalline LN after a calcination step. This method enables a scalable fabrication of a range of complex geometric shapes with a feature resolution down to 30 μm. The patterned LN metasurfaces exhibit a tunable second harmonic generation activity with an isotropic optical response. This approach offers a scalable and low‐cost pathway for manufacturing LN photonics and the potential to fabricate other materials (e.g., barium titanate and lithium tantalate).

Photochemical metal–organic decomposition (PMOD) enables scalable patterning of lithium niobate (LN) metasurfaces under ambient conditions, eliminating the need for cleanrooms or harsh etching. This bottom‐up approach produces complex, diverse, and size‐tunable polycrystalline LN patterns. These structures exhibit tunable isotropic second harmonic generation and require no phase matching, highlighting a simple and scalable route for next‐generation photonic device fabrication.© 2026 WILEY‐VCH GmbH