Atomic spin precession electro-optic modulation detection based on guided mode resonant lithium niobate metasurfaces

Low-frequency noise in detection systems significantly affects the performance of ultrasensitive and ultracompact spin-exchange relaxation-free atomic magnetometers. High frequency modulation detection helps effectively suppress the 1/f noise and enhance the signal-to-noise ratio, but conventional modulators are bulky and restrict the development of integrated atomic magnetometer modulation-detection systems. Resonant metasurface-based thin-film lithium-niobate (TFLN) active optics can modulate free-space light within a compact configuration. In this study, we demonstrate a TFLN metasurface platform that leverages guided mode resonance for efficient phase modulation, achieving a modulation amplitude of 0.063 rad at a frequency of 100 kHz. We exploit the resonance in the TFLN waveguide and obtain a high-quality factor of 166 at a resonant wavelength of 795.8 nm. Using the fabricated modulator, we achieve an optical rotation angle measurement sensitivity of 4 × 10^-7 rad Hz^-1/2 with the modulation. Compared to conventional bulky modulators, the modulator fabricated in this study realizes more than 90% reduction in volume. This study provides a feasible approach for developing miniaturized integrated atomic magnetometers to achieve ultrahigh sensitivity through optical modulation techniques.