Broadband long-wavelength infrared micromechanical photoswitch for zero-power human detection

Abstract

This paper reports on the first demonstration of a long-wavelength infrared (LWIR) micromechanical photoswitch (MP) suitable for human detection with zero-power consumption in standby. The proposed MP employs a highly-efficient broadband IR absorber (η~80%, λ=8-12μm), spectrally matching with the IR radiance of a human body. An ultra-low detection threshold of ~140 nW is experimentally demonstrated for the first time thanks to the high thermal sensitivity (~1.44 nm/nW) and stiffness (~0.033 nN/nm) of the optimized bimaterial actuating beams and the aggressively scaled nanoscale contact gap (<200 nm) maintained by the built-in temperature and stress compensation mechanisms. Such low threshold potentially enables human detection with a lens at a projected distance of 5.7 m.