Electrically tunable plasmonic meta-grating on thin film lithium niobate

Leveraging lithium niobate's electro-optic properties, bound states in the continuum (BICs) offer promising advancements for low-power, high-performance photonic devices. In this study, we present a novel spatial light modulator based on a lithium niobate (LN) with gold nanograting that exploits BIC mechanism to achieve high quality (Q) factor resonances. By intentionally breaking the symmetry of the gold meta-grating, a true BIC mode is transformed into quasi-BIC, to enable strong field confinement and enhanced light-matter interactions. The device demonstrates a significant electrical driving thermo-optic modulation amplitude of 23% under a low driving voltage of 1 V, with a tuning efficiency of 6.59 nm/V at a central wavelength of 1533 nm. The experimental results, largely consistent with simulations, reveal a Q factor of 552 for the quasi-BIC mode. Additionally, the modulator exhibits a rise time of 22.8 ms. This work showcases a promising approach for developing compact, low-power, high-performance tunable photonic devices, with potential applications in optical communication, sensing, and signal processing.