Ultra-sensitive thin-film lithium niobate electric field sensor based on a folded Mach–Zehnder interferometer

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Electric field (E-field) sensing plays great roles in both scientific research and engineering applications. E-field sensors with high sensitivity to detect faint signals are still lacking. Thin-film lithium niobate (TFLN) E-field sensors have been reported to have lots of advantages. In this study, we demonstrated a high-sensitivity TFLN E-field sensor based on a folded Mach–Zehnder interferometer with a segmented electrode. Such a design significantly extends the effective modulation length within a small footprint (2.8 × 11 mm2), overcoming the sensitivity limitations of conventional MZI sensors. The sensor operates from 10 MHz to 550 MHz and achieves a record sensitivity of 3.25 μV/m/Hz1/2 at 75 MHz among MZI-based sensors.