A Tunable Optical Cavity for Enhancement of Nb5N6Microbolometer THz Detector Absorption

Based on substrate cavity effect, an asymmetric coupled Fabry-Perot (FP) cavity is constituted by simply placing a movable metallic planar mirror in the back of the silicon substrate. The incident THz radiation onto the Nb
₅
N
₆
microbolometer can be effectively manipulated by changing the substrate-mirror distance to modulate the phase relation between the reflect wave and the incident wave. The distinct responsivity control can be observed and the experiments are well explained by numerically analyzing the radiation dynamics that highlights the role of FP cavity effect. All results discussed here can be extended to broad range of frequency and other type of THz detectors.