Dual-layer capacitance-loaded thin-film lithium niobate electro-optic modulator with high modulation efficiency

Thin film lithium niobate (TFLN) modulators with low driving voltage and high bandwidth are desirable for fiber-optic communication. Enhancing the modulation efficiency of TFLN modulators can reduce the device length while maintaining a low driving voltage, leading to more dies per wafer and subsequently lower fabrication cost. However, waveguide loss induced by metal absorption limits the electrodes spacing, thereby constraining the modulation efficiency. Here, we propose a novel dual-layer capacitance-loaded electrode structure to improves the modulation efficiency while maintaining a low absorption loss. We experimentally demonstrate a C-band (1550 nm) modulator featuring a half-wave voltage of 3.2 V, a modulation length of 5 mm, and a 3-dB bandwidth over 67 GHz.