Detection of terahertz radiation from 2.52 THz CO2 laser using a 320 × 240 vanadium oxide microbolometer focal plane array

Abstract

Real-time, continuous-wave terahertz (THz) detection and imaging are demonstrated with a 2.52 THz far-infrared CO₂ laser and a 320 × 240 vanadium oxide (VO_x) micro-bolometer focal plane array. A nanostructured titanium (Ti) thin film absorber is integrated in the micro-bridge structure of the VO_x micro-bolometer by a combined process of magnetron sputtering and reactive ion etching (RIE), and its improvement of THz absorption is verified by an optical characteristics test. By eliminating the background signal, non uniformity and noise with proper circuits, the output dynamic range of the readout integrated circuit (ROIC) is 0.4–3.6 V and the fixed pattern noise (FPN) is less than 10 mV. After vacuum packaging, the detector is used for THz detection and achieves a responsivity of 2186 v/w and a NEP of 45.7 pW/Hz^1/2. With this detecting system, THz imaging through a wiping cloth and envelope is demonstrated, showing the feasibility of real-time security checking and mail screening.