Resonantly Enhanced Electric-Field Sensing of Etchless Thin Film Lithium Niobate via Quasibound Sates in the Continuum

TL;DR

This paper proposes a highly sensitive, etchless lithium niobate-based electric-field sensor utilizing quasi-BIC resonance for localized field enhancement, achieving high tuning sensitivity and potential for detecting extremely weak electric fields.

Contribution

The paper introduces a novel etchless lithium niobate sensor with hybrid coupling-grating systems supporting high-Q quasi-BIC resonance, enabling enhanced electric field detection sensitivity.

Findings

Tuning sensitivity of 40.8 nm/V achieved

Minimum detectable electric field of 24.5 mV demonstrated

Device bandwidth exceeds 154 GHz

Abstract

Electric field detection has been widely utilized in many fields such as scientific research and integrated circuits. To enhance the tuning sensitivity of E-field sensor, in this paper, we theoretically proposed a highly sensitive E-field sensor composed of etchless lithium niobate (LN) material and hybrid coupling-grating systems in the visible near-infrared regime. Such configuration supports high-quality factor quasi-BIC resonance, which generates strong localized field confinement. Due to the large electro-optic coefficient of LN material, one can shift the wavelength and reflection ratio of resonance by tuning the refractive index of LN material. An analytical theory is carried out to explain the relationship between the refractive index variations and the applied voltages, so we successfully obtained a tuning sensitivity of 40.8 nm/V and a minimum detectable electric field amplitude of 24.5 mV with wavelength resolution of 1 nm. Due to the low parasitic capacitance of LN material and high conductivity of gold film and ITO layer which are utilized as the electrodes, the 3dB bandwidth of the devices should exceed 154 GHz. And we believe that such a surface-normal E-field sensor has extensive potential for the extremely weak electric field detection.