Continuous Wave THz Imaging System Based on Glow Discharge Detector Lei Hou, Hongkyu Park and X.-C. Zhang Research Institute Troy NY, Center for Terahertz Research, Rensselaer Polytechnic Institute, Troy, NY 12180 Introduction Challenges in THz Imaging Glow Discharge Detector A Glow discharge detector (GDD), based on a To use THz imaging for Real-life applications A GDD is a commercial neon lamp filled with low commercial neon lamp, was used in a continuous wave - THz source: efficiency and compactness pressure inert gases with Penning mixture and (CW) terahertz (THz) imaging system. The -THz detector: response speed, sensitivity, operating typically coated with phosphor. Two electrodes are resp nsivity and n ise equivalent p wer (NEP) of a responsivity noise power f temperature, peratin temperature operating spectrum and lamp, ionize placed parallel within the lamp which i nize the inert GDD are 70 V/W and 1.26 × 10-6 W/Hz1/2, cost effectiveness gases, resulting in discharge current. The incident respectively. The performance of the GDD can be THz wave enhances ionizing collisions of electrons improved as commercial neon lamps do not have an THz NEP Response with neutral atoms and causes an increase in the Price optimized structure as a THz detector. The Detector (W/Hz-1/2) speed discharge current. preliminary results indicate that a well-designed GDD Schottky diode 10-10 ~ 10-12 ~ kHz expensive Low cost (less than $1) will be an excellent THz detector with microsecond Electronic ruggedness response time, wide spectral range (0.1 ~ 10 THz), p , p g ( ), Pyroelectric 10-11 ~ 10-12 < 100 Hz expensive Broad spectral range (MW, IR, UV) p g ( , , ) high responsivity (> 1000 V/W) and low NEP (< 10-12 Room-temperature operation W/Hz1/2). Golay cell 10-11 ~ 10-12 ~ 20 Hz expensive Fast response speed (microsecond rise time) CW THz Imaging System Responsivity and NEP of GDD THz Images (0.2 THz) 68 subnormal normal abnormal -100 discharge current golw golw golw a: 3.0 mA a U (V) 66 b: 5.3 mA /Hz) -110 c: 6.7 mA d: 8.1 mA rms b e: 10.2 mA 2 Sv (dbV 64 c -120 d ivity (V/W) e 60 -130 0 20 40 60 80 100 Fi st Aid Kit First THz i TH image by GDD b responsi 40 frequency (kHz) Schematic diagram of the 0.2 THz imaging Noise spectrum 20 system based on GDD. 0 2 4 6 8 10 current (mA) noise power spectral density 20 NEP = modulation signal Amplified responsivity (Gain: 130) responsivi ty THz signal THz amplitude (mV) 10 = 1.26 × 10 − 6 W / Hz amplitud (a.u.) 6 300 when e 4 de 2 0 0 :discharge current of GDD is 8.8 mA PC Board GDD Schottky diode :chopping frequency is 900 Hz α (1/cm) 200 0 1 2 3 f (THz) -10 Deficient NEP caused by: 100 References -20 Absorption of glass wall 0 1 2 3 4 5 1. A. Abramovich, N. S. Kopeika, D. Rozban and E. time (ms) 0 0.5 1.0 1.5 2.0 2.5 3.0 Scattering of glass wall Farber, Appl. Opt. 46, 7207-7211 (2007). 0.2 THz signal measured from the GDD by an freqnency (THz) Mi h between TH b Mismatch b THz beam 2. D. Rozban, N. S. Kopeika, A. Abramovich, and E. oscilloscope. Chopping frequency : 900 Hz. Absorption coefficient of glass wall size and gap size of GDD Farber, J. Appl. Phys. 103, 093306 (2008). This material is based upon work supported by the U.S. Department of Homeland Security under Award Number 2008-ST-061-ED0001. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied of the U.S. Department of Homeland Security.
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