Thin-film lithium niobate modulators for non-invasive sensing of high-frequency electric fields

We propose a non-invasive, large-bandwidth electro-optic (EO) detection scheme for high-frequency electric fields using thin-film lithium niobate Mach–Zehnder interferometers. Our proof-of-concept device is capable of detecting high-strength electric fields, such as those present in x-ray free electron lasers and linear accelerators. The proposed detection scheme utilizes an off-the-shelf C-band fiber optic continuous-wave laser and optical spectrum analyzer, which has a lower system cost and footprint compared to bulk-crystal-based schemes. Towards this objective, fabricated devices are characterized in the 1–40 GHz frequency range to estimate the detection threshold, detection bandwidth, and EO modulation strength. The characterized device exhibits a 0.13 V ⋅ m − 1 ⋅ H z − 1 / 2 normalized electric field sensitivity. By extrapolating the measured frequency response, it is expected that the characterized device will be able to detect free-space electric fields up to 150 GHz.