Detection of terahertz radiation from quantum cascade laser using vanadium oxide microbolometer focal plane arrays

Abstract

Abstract The authors made experiments on real-time imaging of THz radiation from Quantum Cascade Laser (QCL), using vanadium oxide (VOx) microbolometer in frared focal plane arrays (IRFPAs) of 320x240 with pitches of 37 µm and 23.5 µm as well as 640x480 with 23.5µm pitch. The QCL has such parameters as 3.1 THz emission frequency and time averaged power of a bout 10 µW at 15K operation temperature. Using QCL and current VOx IRFPAs, Noise Equivalent Power (NEP) was measured at 3.1 THz and found 200~300 pW. To improve NEP or THz signal, THz absorption layer was added to pixel structure of the current 320x240 IRFPA with 23.5µm pitch and THz transmissivity of package window was also increased. NEP values for improved FPAs were measured and NEP value of 40 pW was obtained at 3.1 THz. Finally, effect of pixel integration on NEP was investigated for frame integration of 64 frames and it is found that NEP value as low as 1 pW is achievable. Keywords : Terahertz, Real-time imaging, Microbolometer, Focal plane arrays, THz absorption layer 1. INTRODUCTION