Zero-Power Flame Detector with Wide Field-of-View Based on Plasmonically-Enhanced Micromechanical Photoswitch

This paper reports on the first demonstration of a zero-power flame detector based on a plasmonically-enhanced micromechanical photoswitch (PMP) that is optimized for the detection of characteristic infrared (IR) radiation at
$4.3 \mu \mathrm{m}$
emitted by hydrocarbon flames. In particular, a narrowband cross-type plasmonic absorber (absorptance >85%, bandwidth ∼15%) is integrated with a micromechanical photoswitch with improved thermal-mechanical performance (thermal sensitivity ∼2 nm/nW). The resulted record low IR detection threshold ∼5 nW leads to an experimental demonstration of the detection of a small open flame from a handheld butane torch ∼5-m away in a lab environment, which corresponds to a detection range of ∼70 m in industrial standard test. Thanks to the omnidirectional property of the plasmonic absorber, a field-of-view of ∼125°, nearly 40% wider than commercial flame detectors is recorded. Unlike any existing flame detectors, the demonstrated technology does not consume any electrical power at standby, hence one of the best candidates for the implementation of a wireless sensor network for long-term fire monitoring.