A False Alarm-Free Zero-Power Micromechanical Photoswitch

Zero-power infrared (IR) sensors based on Plasmonically-enhanced Micromechanical Photoswitches (PMPs) have recently been demonstrated, showing the capability to detect IR signatures with near-zero standby power consumption. However, current prototypes fail to discriminate between a targeted IR source (e.g. a flame) and a spurious one (e.g. an exhaust plume) having overlapping IR emission wavelengths, potentially getting triggered ON in the presence of strong interference and creating false alarms. This paper reports on the first experimental demonstration of a PMP augmented with an integrated passive false-alarm prevention mechanism to effectively desensitize it to spurious IR sources while maintaining a small footprint and near-zero standby power consumption. By incorporating two different narrowband plasmonic absorbers on a PMP - one tuned to the targeted IR wavelength and the other to a spurious wavelength - we show that the electrical contacts close in response to IR radiation at the targeted wavelength and remain open in the presence of spurious wavelengths, thereby preventing false alarms. Such an enhanced PMP prototype targeting flame detection with a threshold ~600 nW (minimum detectable IR power) is demonstrated showing zero false alarm to interfering IR sources. The increased reliability enabled by this technique makes PMP technology an ideal candidate for the implementation of large-scale maintenance-free wireless sensor networks with unlimited battery lifetimes.