Slow-light microring resonators on thin-film lithium tantalate

Thin-film lithium tantalate (TFLT) is considered a key next-generation platform for integrated photonics due to its strong electro-optic effect and low propagation loss. This work demonstrates for the first time, to the best of our knowledge, the design and fabrication of a photonic crystal ring resonator (PhCR) along with its electro-optic modulator on TFLT. The fabricated PhCR achieves high quality factors of 2.16 × 10⁵ and 1.08 × 10⁵ in the air and dielectric bands, respectively, and a pronounced slow-light effect (with a slow-light factor S > 3). This confirms the platform's capability to support both high-Q optical resonance and effective dispersion engineering. The PhCR modulator, constructed with a reduced bending radius, features a low half-wave voltage-length product of 1.71 V·cm and an electro-optic bandwidth of 44 GHz, demonstrating its potential for high-speed signal processing. This work fills a critical gap for slow-light photonic crystal devices on TFLT and establishes an experimental foundation for future active and multifunctional slow-light photonic devices on this platform.