Uncooled low-noise optomechanical sensors on thin-film lithium niobate

Optomechanical transduction harnesses the interaction between optical fields and mechanical motion to achieve sensitive measurement of weak mechanical quantities with inherently low noise. Lithium niobate combines low optical loss, strong piezoelectricity, a high intrinsic f × Q_m factor, and low thermal conductivity, making it promising for exploring optomechanical platforms targeting thermal sensing applications. Here, we demonstrate an integrated optomechanical platform on thin-film lithium niobate with precisely engineered optical, mechanical, and thermal fields within a compact 40 μm-diameter footprint. The platform integrates suspended microring resonators with ultrathin central membranes, reducing effective mass and thermal capacitance while maintaining a high intrinsic optical quality factor Q_o of 10⁶ and a mechanical quality factor Q_m of 1117, which increases to 5.1 × 10⁴ upon optomechanical oscillation. The two-step etching suppresses thermal dissipation into the silicon substrate and enhances thermal sensitivity, achieving a temperature coefficient of frequency of -124 ppm K^-1, a measurable loaded thermal response time of 7.2 μs, and a noise-equivalent power of 6.2 nW Hz^-1/2 at 10 kHz and room temperature. This compact and scalable platform opens new opportunities for high-sensitivity thermal sensing and power detection and supports heterogeneous integration with infrared absorbers for uncooled infrared detection, thereby paving the way toward large-format infrared sensing arrays with low-noise, all-optical readout. Through co-design of the thermal, mechanical, and optical domains, we demonstrate low-noise sensing with a microsecond-scale response time at room temperature in air.