Ferroelectric Flakes Enable Reconfigurable Optical Frequency Conversion on Photonic Chips

Researchers have achieved electrically reconfigurable second-harmonic generation on an integrated photonic chip by coupling thin layers of ferroelectric niobium oxide dibromide with a silicon nitride microring resonator. The device architecture, demonstrated in an experimental study published in Nature Nanotechnology, demonstrates dynamic electrical control over cavity-enhanced nonlinear optical responses, while also enabling dual-channel optical edge detection.

Niobium oxide dihalide films are known to exhibit second-harmonic generation efficiency that scales with material thickness, a characteristic arising from their weak interlayer electronic coupling. Despite this favorable nonlinear optical scaling, the practical deployment of these two-dimensional materials within integrated nonlinear photonics has previously been constrained by a lack of robust, dynamic electrical tuneability.

To address this limitation, the research team integrated ferroelectric NbOBr2 flakes with thicknesses ranging from 20 nm to 40 nm onto a silicon nitride microring resonator cavity. In this composite platform, NbOBr2 provides strong second-order optical susceptibility stemming from its intrinsic inversion-symmetry breaking, paired directly with electrically switchable in-plane ferroelectric polarization.

By modulating the Schottky barrier established at the interface between the NbOBr2 flake and the metal contacts, ferroelectric switching directly governs carrier injection, free carrier absorption, and optical dispersion. These electro-optic adjustments modify the resonance conditions, thereby tuning the cavity-enhanced second-harmonic response.

In laboratory measurements under continuous-wave optical excitation, the integrated microring resonator device reached a second-harmonic generation conversion efficiency of 158% W−1. Alongside this frequency conversion efficiency, the electrical control mechanism yielded a modulation depth of 53%, confirming substantial electro-optic tuneability on chip.

Beyond volatile modulation, the in-plane ferroelectric polarization states within the NbOBr2 layer can be programmed across multiple distinct levels and retained after the electrical field is removed, providing non-volatile optical control. Utilizing the fundamental pump transmission and the frequency-converted second-harmonic signals as complementary operational channels, the researchers further implemented on-chip dual-channel edge detection for optical processing.

Subject of Research: Electrically reconfigurable on-chip second-harmonic generation using ferroelectric NbOBr2

Article Title: Dynamic electrical control of on-chip second-harmonic generation with ferroelectric NbOBr2

Article References: Gong, X., Duan, R., Ming, W., Yang, Y., Huo, J., Lee, S.-G., Guo, S., Guo, X., Leong, J., Singh, L., Chen, W., Wang, Q. J., Chang, W., Gong, Y., Tay, B. K., Liu, H., Zhao, X., Wu, Q., Ang, L. K., … Chae, S. H. (2026). Dynamic electrical control of on-chip second-harmonic generation with ferroelectric NbOBr2. Nature Nanotechnology. https://doi.org/10.1038/s41565-026-02331-w

Image Credits: AI Generated

DOI: 10.1038/s41565-026-02331-w

Keywords: nonlinear photonics, second-harmonic generation, ferroelectric materials, niobium oxide dibromide, silicon nitride microring resonator, integrated photonics, optical edge detection, non-volatile optical control, Dynamic, electrical, control, on-chip