Dual-Mode Thermal-Piezoresistive Coupled Resonators for Fast and Stable NIR Measurements with Differential Output

This study reports a resonant Near-Infrared (NIR) detector based on dual-mode, self-oscillating Thermal-Piezoresistive Coupled Resonators. The resented device alleviates the current trade-offs between resolution and response time in Microelectromechanical Systems (MEMS) thermal detectors. The thermal-piezoresistive coupled resonators operate simultaneously in the in-phase and out-of-phase modes and the frequency difference between two modes is selected as the output metric. The square-shaped coupling area of the coupled resonators acted as the NIR sensing region because of its low thermal resistance. Our design demonstrated a $700~\mu {s}$ response time, achieving 700-fold improvement compared to the conventional single-frequency output methods. Further, the differential output method inherently compensates for temperature drift, significantly increasing the immunity of device to thermal crosstalk by a factor of 25. A noise equivalent power density resolution of 253 pW/$\sqrt {\textit {Hz}}$ is achieved.