Detection and upconversion of three-dimensional
MMW/THz images to the visible
Avihai Aharon (Akram),
1,2,
* Daniel Rozban,
1,3
Avi Klein,
1
Amir Abramovich,
1
Yitzhak Yitzhaky,
3
and Natan S. Kopeika
2,3
1
Department of Electrical and Electronic Engineering, Ariel University, Ariel, Israel
2
Department of Electrical and Computer Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel
3
Department of Electro-Optical Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel
*Corresponding author: avihaiak@gmail.com
Received August 15, 2016; revised October 2, 2016; accepted October 2, 2016;
posted October 4, 2016 (Doc. ID 273711); published November 15, 2016
We present an inexpensive technique to obtain a three-dimensional (3D) millimeter wave (MMW) and terahertz
(THz) image using upconversion. In this work we describe and demonstrate a method for upconversion of MMW/
THz radiation to the visual band using a very inexpensive miniature glow discharge detector (GDD) and a silicon
photodetector. We present MMW/THz upconversion images based on measuring the visual light emitting from the
GDD rather than its electrical current. The results show better response time and better sensitivity compared to the
electronic detection performed previously. Furthermore, in this work we perform frequency modulation continu-
ous wave (FMCW) radar detection based on this method using a GDD lamp, with a photodetector to measure GDD
light emission. By using FMCW detection, the range in addition to the intensity at each pixel can be obtained,
thus yielding the 3D image. The GDD acts as a heterodyne mixer not only electronically but also optically. The
suggested 3D upconversion technique using the GDD is simple and inexpensive and has better performance
compared to other MMW/THz imaging systems suggested in the literature. This method provides minimum de-
tectable signal power that is about 6 orders of magnitude better than similar plasma systems due to the very large
internal signal gain deriving from the much smaller electrode separation and resulting in much higher plasma
electric field. © 2016 Chinese Laser Press
OCIS codes: (110.0110) Imaging systems; (110.6795) Terahertz imaging; (110.6880) Three-dimensional
image acquisition; (040.0040) Detectors; (190.7220) Upconversion; (040.5160) Photodetectors.
http://dx.doi.org/10.1364/PRJ.4.000306
1. INTRODUCTION
The use of millimeter wave (MMW) and terahertz (THz)
radiation has increased in recent years, especially in the fields
of spectroscopy [1] and imaging [2,3]. More and more appli-
cations in medicine, communications, homeland security,
material science, and space technology are based on MMW
and THz radiation bands [2–4]. The motivation to use these
bands is that there is no known ionization hazard for biologi-
cal tissue, the atmospheric scattering of MMW and THz
radiation is relatively low, and the penetration through dielec-
tric materials is quite good [2–4]. Furthermore, the lack of
inexpensive room temperature detectors and focal plane
arrays (FPAs) in these spectral regions makes it difficult to
develop some of the above applications, especially those that
require the use of real-time three-dimensional (3D) imaging.
Currently, one of the main goals of MMW and THz technology
is the development of low-cost, fast, highly sensitive, compact,
and room-temperature detectors. Miniature neon indicator
lamps were found to be very good detectors in the MMW
and THz regions. They are also known as glow discharge de-
tectors (GDDs). The GDD is a room temperature detector that
was previously proven to be a very sensitive and inexpensive
MMW/THz radiation detector [5–7], capable of direct and
heterodyne radiation detection [8–10]. FPAs based on GDD
pixels were constructed and experimentally demonstrated
[8]. In those demonstrations, a measurement of GDD electri-
cal current as a function of incident MMW/THz radiation was
carried out. In this work, we demonstrate and experimentally
test an upconversion of MMW/THz radiation to visual light us-
ing a GDD, with a silicon detector to measure the intensity of
GDD output light.
There are already several existing room-temperature MMW
and THz detectors [2,3]. The most popular detectors are Golay
cells, pyroelectric detectors, bolometers, and microbolometers,
many of which are too slow for video frame rates. Among those
detectors, the vanadium oxide (VOx) microbolometer was
found to be suitable for the design of high-resolution FPA im-
aging [2,3]. The disadvantages of using a VOx microbolometer
are low sensitivity and slow response time, as described in de-
tail in Refs. [2,3]. Very fast existing-room-temperature MMW/
THz detectors are based on Schottky diodes. The disadvantage
of these detectors is that they are much less sensitive at the
higher frequencies of the THz band [11]. Furthermore,
Schottky diode performance was compared to GDD perfor-
mance in a THz interferometer [11]. It was found that the
GDD has a higher signal-to-noise ratio, a linear response,
and a faster response time than the Schottky diode [11]. All
the detectors described above are expensive detectors. In this
work we use the GDD, which is a room-temperature detector
with high dynamic range, is very broadband, exhibits fast re-
sponse time, and is rigid, easy to operate, commercially avail-
able, and very inexpensive (costing about $0.20–$0.50 each).
The GDD’s detection mechanism is based on a slight
change of current between the two electrodes of the lamp;
306 Photon. Res. / Vol. 4, No. 6 / December 2016 Aharon (Akram) et al.
2327-9125/16/060306-07 © 2016 Chinese Laser Press