Antenna-coupled microbolometer array for terahertz detection

A novel room-temperature microbolometer for terahertz wave is described in this paper. Each microbolometer in the array consists of a Nb₅N₆ thin film microbridge and a dipole planar antenna. Such antenna-coupled microbolometer behaves very well for detecting signals from 0.2 THz to 0.32 THz, thanks to the fact that the temperature coefficient of resistance of the Nb₅N₆ thin film is as high as -0.7% K^-1. The DC responsivity, calculated from the measured I-V curve, of the microbolometer is about 730 V/W at the bias current of 0.4 mA. A typically noise voltage as low as 10 nV/√Hz lead to a low noise equivalent power (NEP) of 1.5 × 10^-11 W/√Hz for modulation frequencies above 4 kHz. The RF responsivity and corresponding NEP are experimentally shown to be 550 V/W and 2 × 10^-11 W/√Hz, respectively, at 4 kHz for 0.27 THz detecting.