62 / 2022-03-09 11:50:51

High sensitivity thin-film lithium niobate electric field sensor

electric field sensor

Purpose/Aim

High sensitivity electric field (E-field) measurement is a common demand in power system, EMC testing and aerospace. This paper is aimed to demonstrate an E-field sensor with the minimum detectable E-field (E_min) of 0.16 V/m at 10 MHz based on a thin-film lithium niobate platform.

Device design and demonstration

Thin-film lithium niobate (TFLN) is an emerging platform for electro-optic (EO) devices owing to its exceptional EO properties and high compactness. The E-field sensor operates in Mach-Zehnder interferometer configuration is proposed and demonstrated (Fig 1a).

The optical and electrical field distributions in the waveguide is carried out by finite-element-method (Fig 1b, c). The optical waveguides are patterned by UV lithography and dry etching (Fig 1e). The electrodes are prepared by electron beam evaporation and lift-off process (Fig 1d). To ensure single-mode operation, width w and etching depth e of the waveguide are chosen to be 800 nm and 310 nm. Gap between electrode and waveguide is 2.5 μm to provide strong electric field while avoiding metal absorption loss.

Conclusions

We have demonstrated the first E-field sensor on a LNTF platform, with the voltage-length product of 2.98 V∙ cm (Fig 1f) and the predictable E_min of 0.16 V/m at 10 MHz bandwidth.