Hezi Joseph

Inexpensive THz Focal Plane Array Imaging Using Miniature Neon Indicator Lamps as Detectors

Development of focal plane arrays (FPAs) for mm wavelength and THz radiation is presented in this paper. The FPA is based upon inexpensive neon indicator lamp Glow Discharge Detectors (GDDs) that serve as pixels in the FPA. It was shown in previous investigations that inexpensive neon indicator lamp GDDs are quite sensitive to mm wavelength and THz radiation. The diameters of GDD lamps are typically 3-6 mm and thus the FPA can be diffraction limited. Development of an FPA using such devices as detectors is advantageous since the costs of such a lamp is around 30-50 cents per lamp, and it is a room temperature detector sufficiently fast for video frame rates. Recently, a new 8 × 8 GDD FPA VLSI control board was designed, constructed, and experimentally tested. First, THz images using this GDD FPA are given in this paper. By moving around the 8 × 8 pixel board appropriately in the image plane, 32 × 32 pixel images are also obtained and shown here, with much improved image quality because of much reduced pixelization distortion.

A novel self-heterodyne method for combined temporal and spectral high-resolution measurement of wavelength transients in tunable lasers

This letter presents a new experimental optical delayed self-heterodyne method to characterize tunable laser source instantaneous wavelength transients at accuracy of electronic spectrum.

Heterodyne Detection by Miniature Neon Indicator Lamp Glow Discharge Detectors

Miniature neon indicator lamps acting as glow discharge detectors (GDD) are candidates to serve as very inexpensive room-temperature Terahertz radiation detectors and as pixels in THz imaging systems. Previous experiments with GDD devices with THz waves showed good responsivity and noise equivalent power using direct detection. Significant improvement of detection performance is expected using heterodyne detection. Since THz sources are expensive and heterodyne detection requires two sources, we show here a proof of concept at low frequencies. In this paper, we compare the performance of GDDs in direct detection to the performance of GDDs in heterodyne detection at 10 GHz. The experimental results show that heterodyne detection is almost two orders of magnitude more sensitive than direct detection, and that in general sensitivity is inversely proportional to increasing local oscillator power. Heterodyne detection at 300 GHz is also demonstrated.

Super resolution and optical properties of THz double row array based on inexpensive Glow Discharge Detector (GDD) pixels

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 visual and IR radiation. Thus THz imaging is very attractive for homeland security, biological, space, and industrial applications Recently we have found experimentally that inexpensive miniature neon indicator lamp Glow Discharge Detectors (GDD) can be used as THz detectors. Based on the GDD we designed, constructed, and experimentally tested an 8×8 GDD array. In order to improve the performance and the resolution of the THz images a larger array is required. In this work we use a special double row 2×18 moving array detector. The 2×18 GDD array enables us to employ scanning method in order to obtain 36×36 pixel THz images. Furthermore, using this double row array it will be possible to employ super resolution methods. Optical properties such as optical transfer function and measurement of point spread function are presented, as well as first results for the 2×18 GDD array.

mm wave and THz imaging using very inexpensive neon-indicator lamp detector focal-plane arrays

Development of focal plane arrays (FPA) for mm wavelength and THz radiation is presented in this paper. The FPA is based upon inexpensive neon indicator lamp Glow Discharge Detectors (GDDs) that serve as pixels in the FPA. It was shown in previous investigations that inexpensive neon indicator lamps GDDs are quite sensitive to mm wavelength and THz radiation. The diameter of GDD lamps are typically 3-6 mm and thus the FPA can be diffraction limited. Development of an FPA using such devices as detectors is advantageous since the costs of such a lamp is around 30-50 cents per lamp, and it is a room temperature detector sufficiently fast for video frame rates. Recently a new 8×8 GDD FPA VLSI board was designed, constructed, and experimentally tested. First THz images as well as DSP methods using this GDD FPA are demonstrated. Super resolution was achieved by moving the 8×8 pixel board appropriately in the image plane so that 32X32 pixel images are also obtained and shown here, with much improved image quality because of much reduced pixelization distortion.

Oversampling advances in millimeter-wave scan imaging using inexpensive neon indicator lamp detectors

Abstract. In recent years, much effort has been invested to develop room temperature inexpensive, but sensitive, millimeter wave (MMW) and terahertz (THz) detectors that can be used as pixels in focal plane arrays, which is important for real-time imaging. A new 18×2 neon indicator lamp MMW/THz scanner was developed. The components of the camera include horizontally shifted two-column glow discharge detectors in a scanning array. The detectors, costing about 50 cents each, are wired to a preprocessing card, a VLSI board, and a motor for scanner movement. A description of the VLSI Verilog programmable hardware of the new scanner, the physical architecture, the software user interface, and imaging results at 97 GHz are presented. At this stage, the emphasis is focused on the lamp exposure time and spatial resolution when the scanning is performed horizontally. In the future it is planned to expose all pixels simultaneously for real-time imaging. New software capabilities allow the application of digital image enhancement algorithms. Fast scanning permits obtaining images in 1 to 5 s. Oversampling yields a sharper edge response and a higher signal-to-noise ratio.

A novel self-heterodyne filtering method by wavelength shift keying Modulation for optical CDMA

We propose and demonstrate a new method of optical code-division multiple access (CDMA) based on self-heterodyne filtering. As compared to most CDMA systems, low spectrum spreading is required, thus enabling longer reach transmission capability.

Low cost plasma Terahertz heterodyne image detection

Miniature inexpensive neon indicator lamp plasma glow discharge detectors (GDD) are excellent candidates to serve as room temperature, low cost, terahertz (THz) radiation detectors and as pixels in THz imaging systems. Heterodyne amplification of low power signals via higher power reference beams is very important for THz imaging systems because it permits detection of much lower object beam intensities. An experimental result of 300GHz heterodyne detection by a single commercial GDD device costing about 30 cents is presented here. In heterodyne image detection a picture is taken of interference fringes or a hologram deriving from a coherent reference wave and a coherent wave reflected from or transmitted through an object. Transmission with in-line or zero angles between those two waves is important to widen the fringes. The GDD detector is transparent, so that its possible to receive radiation from both sides, at 0 and 180 degree. This permit receiving the wave reflected from or transmitted through an object at 0 degree and the reference wave from the opposite direction at 180 degree. Such interference fringe widening can permit heterodyne direct imaging of the object instead of imaging the interference pattern.

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

The properties of terahertz (THz) radiation are well known. They penetrate well most nonconducting 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.

First operation of 8×8 glow discharge detector VLSI focal plane array toward mm wave and THz radiation video rate imaging

A new kind of 8×8 focal plane array (FPA) based on glow discharge detector (GDD) elements was constructed and tested experimentally. First THz images of this FPA are presented. The data acquisition of this system is performed with a special VLSI board designed for this system. Previously, signal detection of the FPA elements was based upon a lock in amplifier (LIA) which limited the rate of image formation. This was in order to detect weak signals required for stand-off remote detection. Switching mode is necessary in order to save energy but stabilization time of the GDD found to be 0.5 sec. Recent investigations proved that it is possible to overcome the above timing limitations. It was shown that heterodyne detection yielded 40 times more sensitivity than the direct detection, thus in many circumstances obviating the need for a LIA. Moreover, GDD stabilization time of less than 1 msec was achieved. These developments should enable video rate THz imaging using GDD FPAs.