Efficient electro-optic modulators on thin-film lithium niobate with non-centered waveguides and high-permittivity cladding

Advances in integrated photonics require electro-optic modulators that deliver a wide bandwidth, alongside reduced driving voltage and a minimal footprint. Thin-film lithium niobate (TFLN) provides a strong electro-optic response, making it suitable for such applications. However, lowering the half-wave voltage (V_π) often comes at the cost of increased radio-frequency (RF) loss or added fabrication complexity. This work presents a compact TFLN modulator design that avoids these trade-offs by simultaneously incorporating three targeted enhancements: a high permittivity cladding to boost RF field confinement, an asymmetric waveguide layout to increase modulation efficiency, and thick electrodes to minimize microwave loss. The proposed structure achieves a voltage-length product (V_π·L) of 1.34 V·cm and a 3-dB bandwidth beyond 120 GHz, all within a simplified fabrication flow and without compromising optical performance.