Development of a nanograting substrate and polarization independent nanowire absorber for a nanowire membrane microbolometer

Abstract

In recent times, the demand for non-contact infrared sensors, such as thermal cameras used for wildfire monitoring, airports, and hospitals, has increased due to climate change-induced events like wildfires and infectious diseases like COVID-19. The commonly used non-contact infrared sensor for civilian applications, the microbolometer, has been designed by Honeywell since the 1970s. This structure employs a long bridge design to reduce thermal conductivity because the film membrane cannot contribute to thermal conductivity. This prevent to improve microbolometer NETD performance. Here in, the author proposes a nanowire structure with lower thermal conductivity than film. However, the absorption-lowering issue of nanowires caused by the polarization effect also must be addressed. This paper uncovers the reasons for the low TM wave absorption of nanowires through Optical Circuit and FDTD simulation, proposing a Flange nanowire structure to overcome this limitation. The effects of the Flange nanowire structure are confirmed through FDTD simulation, Optical Circuit analysis, and FT-IR measurement. Therefore, this paper demonstrates the applicability of the nanowire structure as the membrane of a microbolometer and nanowire structure can contribute to NETD performance enhancement.