THz Imaging using Glow Discharge Detector (GDD) focal plane arrays and large aperture quasi optic mirrors.

N. S. Kopeika1, A.Abramovich2, H. Joseph1,2, D. Rozban1,2, A. Akram1,2, A. Levanon

O. Yadid-Pecht1, A. Belenky1, and S. Lineykin1

1Department of Electro-Optical Engineering, Ben Gurion University of the Negev, Beer-Sheva, Israel

2Department of Electrical and Electronic Engineering, Ariel University center of

Samaria, Ariel, Israel

ABSTRACT

The properties of terahertz (THz) radiation are well known. They penetrate well most non-conducting media; there are no known biological hazards, and atmospheric attenuation and scattering is lower than for visual and IR radiation.

Recently we have found that common miniature commercial neon glow discharge detector (GDD) lamps costing typically about 30 cents each exhibit high sensitivity to THz radiation, with microsecond order rise times, thus making them excellent candidates for such focal plane arrays.

Based on this technology we designed, built and tested 4X4 and 8X8 GDD focal plane arrays. A line vector of 32 GDD pixels is being designed in order to increase the number of pixels in such arrays and thus the image resolution. Unique large aperture quasi optic mirrors were design and tested experimentally in this work. A new technology of light weight large aperture mirrors is proposed in this work. In this case a metal coating on plastic substrate is demonstrated. According to first experiments this technology proves to reliable with minimal deformation in LAB conditions. THz Images at 100 GHz were taken using this new inexpensive technology with good quality and resolution.

Keywords: THz detector, THz imaging, quasi-optical design, plasma, glow discharge

1 Introduction

Imaging systems in the electromagnetic spectrum between 100 GHz and 10 THz are required for applications in medicine, communications, homeland security, and space technology. This is because there is no known ionization hazard for biological tissue, and atmospheric attenuation of terahertz (THz) radiation is low compared to that of infrared and optical rays. The lack of inexpensive room temperature detectors and FPAs in this spectral region makes it difficult to develop detection and imaging systems.

A candidate for FPA pixels is miniature neon indicator lamps such as N523 of international

light technology (Peabody, MA) which was tested experimentally and found to be a very good THz detector1. NEP is on the order of 10-9 W/Hz1/2, and rise time is on the order of a microsecond. The mechanism of detection in such a Glow Discharge Detector (GDD) involves both enhanced ionization 2-7 and enhanced diffusion current 2, 3, 6, 8-10 caused by the incident terahertz wave. The former increases

Millimetre Wave and Terahertz Sensors and Technology III, edited by Keith A. Krapels, Neil A. Salmon,Proc. of SPIE Vol. 7837, 783708 · © 2010 SPIE · CCC code: 0277-786X/10/$18 · doi: 10.1117/12.864852

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knowledgm

authors are grsors Directoradvedi, Schwart

ferences

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shape of the form due to thected since suectors. The difimage in Fighe number of imiting nonun

were divided inpresented usinsity THz beam

ages of “F” shrection algorith

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ments

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object is cleahe nonuniformuch devices arffraction effec

g. 6. For lowef gray levels inniformity was nto 3 levels; eng MATLAB

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after employinthe edges can

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the 8X8 GD” shape imagedesign and com

viewed in Fig

US Office of NInstitute for

ensler Familie

ieka, N., S., Rvol.46, No 29

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arly seen in thmity of the GDre manufacturcts in Fig 6 arer THz beamn THz imagesdone using t

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he “F” shape o

before employ

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he image of FDD pixel respred as inexpenre dominant a

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Fig. 6. The inponse and the nsive indicatoraround the smathe obtained ihresholding caDSP algorith

erent region ofnstrates this co

ction algorithm

hm the “F” shn effects. The

this experimment with thees and minim

rmy Night Visogies Researc

ort.

nexpensive de

or studying dis

ntensity of theelectrical cir

r lamps ratherall parts and eimage degradan be used to

hm: the readouf pixel readouorrection algor

m (Left); and

hape image cacorrected ima

mental work. e simulation re

mize the diffra

sion and Electch named fo

etector for tera

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e “F” rcuits. r than edges dation

limit uts of ut, the rithm

after

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ahertz

ases",

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