We demonstrate an optical method for sensitivity enhancement for LC resonant MM’s, using meta-plate which act as plasmonic enhancer by increasing the electric field concentration in the active area of the metasurface. This makes the MM resonance ultra-sensitive to the tiny changes of particle size/concentration under test spread on the metasurface, contributing to enhanced spectral shift (ΔF). The meta-plate also makes the Si substrate optically lossless and transparent in THz, enabling the full effect of MM resonance without any substrate losses in the transmission spectra. This work also demonstrates an extended concept of de-coupling MM-resonance from the substrate’s Fabry-Pérot (FP) oscillations by de-trapping of the THz radiation from the MM substrate, resulting in the improved quality-factor of the MM resonance and overall plasmonic enhancement on the metasurface. The plasmonic enhancer meta-plate increases the ΔF by eight-fold compared to MM’s fabricated on conventional Si substrates.
We present breathalyzer-based prompt screening technology that can detect and screen multiple respiratory diseases using exhaled breath of a patient, collected on an LC resonant metasurface, demonstrating a spectral red-shift (ΔF). We categorized ΔF for multiple respiratory diseases, which do not overlap. This was physically possible by removing the constraint of detection limit in metamaterials, along with significant sensitivity enhancement physics. This work opens a whole new opportunity to detect and screen multiple lung and breath diseases with one simple and prompt breath test, owing to the multifold sensitivity enhancement physics.
The use of dual cameras in parallax in order to detect and create 3-D images in mobile devices has been increasing over the last few years. We propose a concept where the second camera will be operating in the short-wavelength infrared (SWIR—1300 to 1800 nm) and thus have night vision capability while preserving most of the other advantages of dual cameras in terms of depth and 3-D capabilities. In order to maintain commonality of the two cameras, we propose to attach to one of the cameras a SWIR to visible upconversion layer that will convert the SWIR image into a visible image. For this purpose, the fore optics (the objective lenses) should be redesigned for the SWIR spectral range and the additional upconversion layer, whose thickness is <1 μm. Such layer should be attached in close proximity to the mobile device visible range camera sensor (the CMOS sensor). This paper presents such a SWIR objective optical design and optimization that is formed and fit mechanically to the visible objective design but with different lenses in order to maintain the commonality and as a proof-of-concept. Such a SWIR objective design is very challenging since it requires mimicking the original visible mobile camera lenses’ sizes and the mechanical housing, so we can adhere to the visible optical and mechanical design. We present in depth a feasibility study and the overall optical system performance of such a SWIR mobile-device camera fore optics design.
A new concept of short wavelength infrared (SWIR) to visible upconversion integrated
imaging device is proposed, modeled and some initial measured results are presented. The
device is a hybrid inorganic-organic device that comprises six nano-metric scale sub-layers
grown on n-type GaAs substrates. The first layer is a ~300nm thick PbSe nano-columnar
absorber layer grown in (111) orientation to the substrate plan (100), with a diameter of 8-
10nm and therefore exhibit quantum confinement effects parallel to the substrate and bulk
properties perpendicular to it. The advantage of this structure is the high oscillator strength
and hence absorption to incoming SWIR photons while maintaining the high bulk mobility
of photo-excited charges along the columns. The top of the PbSe absorber layer is coated
with 20nm thick metal layer that serves as a dual sided mirror, as well as a potentially
surface plasmon enhanced absorption in the PbSe nano-columns layer. The photo-excited
charges (holes and electrons in opposite directions) are drifted under an external applied
field to the OLED section (that is composed of a hole transport layer, an emission layer and
an electron transport layer) where they recombine with injected electron from the
transparent cathode and emit visible light through this cathode. Due to the high absorption
and enhanced transport properties this architecture has the potential of high quantum
efficiency, low cost and easy implementation in any optical system. As a bench-mark,
alternative concept where InGaAs/InP heterojunction couple to liquid crystal optical spatial
light modulator (OSLM) structure was built that shows a full upconversion to visible of
1550nm laser light.
A novel integrated two terminal structure of Quantum Well Infrared Photodetector (QWIP) with bias controlled dual-band detection at the long wavelength infrared (LWIR) and near infrared (NIR) atmospheric windows is demonstrated. The LWIR sensor is based on a GaAs/AlGaAs standard QWIP, while the NIR sensor is based on a strained InGaAs/GaAs quantum wells structure. The InGaAs/GaAs quantum wells are embedded in a heterostructure bipolar transistor (HBT) structure, which enables high gain and rapid switching capabilities between the two spectral bands. The GaAs/AlGaAs and InGaAs/GaAs monolithic structure allows fabrication of large focal plane array (FPA) that can be operated using a standard two-terminal readout circuit (ROIC). Such FPA configuration allows simultaneous imaging of a NIR laser spot superimposed on a thermal imaging scene.
A candidate for IR detectors for third generation thermal imageing systems is the QWIP. ELOP has gone through five years of development and evaluation of QWIP focal plane arrays and QWIP based thermal imaging system as a technology demonstrator. The R/D results are 320×256 QWIP based thermal imaging system operating in the 8-10μm band and a QWIP focal lpane array that operates simultaneously at the LWIR and NIR. A few aspects of commercializaiton of the QWIP are described focusing on the dark current issue. The QWIP as a multispectral sensor is referred to, especially the sensitivity of the QWIP by means of NETD in comparison with other optional multispectral detectors.
A decision of choosing the right detector technology for third generation thermal imaging systems is directly derived from the expectations and the requirements of these systems. It is now evident that third gen. thermal imager will still need the higher resolution capabilities as well as capabilities in multispectral detection and polarization sensitivity. Four technologies candidates are analyzed; the field-proved HgCdTe (MCT), uncooled microbolometer technology, Antimonide based materials and quantum well infrared photodetectors (QWIP). Taking into accounts the risks, maturity and technologies gap of each technology, we claim that for non-strategic applications (not low background conditions), QWIP technology is the most favorite. The ternary and super lattice Antimonide based material group seems to be theoretically the best alternative, but are not recommended due to it maturity and the high risk involved in this technology. We anticipate large penetration of the uncooled detectors to the low-end and medium-end market. The HgCdTe will still be in progress due to the inertion of the large funding and the strategic importance of this detectors technology.
A 2 stack two color Quantum Well Infrared Photodetector (QWIP) for simultaneously detection of Long Wavelength InfraRed (LWIR) and Near InfraRed (NIR) radiation is demonstrated. The LWIR sensor is based on a regular GaAs/AlGaAs QWIP, while the NIR sensor is based on a strained InGaAs/GaAs multi quantum wells structure. Optical and electrical measurements of the NIR detector and the inclusive device are presented and discussed. Aspects of the monolithic thermal imaging and see spot system are considered. System performance prediction is calculated based on the FLIR92 method, using MATLABR as a platform to the numerical calculations. The system calculations are based on a conversion method of the laser radiation at the target to a thermal like radiation, enabling calculation of the whole system parameters. This method allows one to predict the maximum range of the observing system from the target that still allows detection of the laser spot over the thermal picture.
KEYWORDS: Sensors, Thermography, Electronics, Scanners, Zoom lenses, Telescopes, Signal detection, Digital signal processing, Imaging systems, Single crystal X-ray diffraction
Efforts invested at El-Op during the last four years have led to the development of TADIR - engineering model thermal imager, demonstrated in 1998, and eventually to the final production version of TADIR to be demonstrated in full operation during 1999. Both versions take advantage of the high resolution and high sensitivity obtained by the 480 X 4 TDI MCT detector as well as many more features implemented in the system to obtain a state of the art high- end thermal imager. The production version of TADIR uses a 480 X 6 TDI HgCdTe detector made by the SCD Israeli company. In this paper, we will present the main features of the production version of TADIR.
We present a model for QWIP-based thermal imagers which allows us to study the effects of the main system parameters on system performance. We use the model to illustrate some of the issues involved in choosing system parameters using a sensitivity analysis. We then present a methodology for choosing the optimal system parameters which takes the constraints presented to the system, such as cost, as an integral part of the model. We propose the use of a benefit- function and a cost-function that allow us to measure the cost-benefit ratio for every system. We use this ratio as the merit figure of the system and optimize for maximal cost- benefit.
'TADIR' is a new high-end thermal imager, developed in El-Op under contract with the Israeli MOD during the last three years. This new second generation thermal imager is based on 480 X 4 TDI MCT detector operated in the 8 - 12 micrometer spectral range. Although the prototype configuration of TADIR was design for the highly demanded light weight low volume and low power air applications, TADIR can be considered as a generic modular technology of which the future El-Op's FLIR applications such as ground fire control system and surveillance systems will be derived from. Besides the detector, what puts the system in the high-end category are the state of the art features implemented in each system's components. This paper describes the system concept and design considerations as well as the anticipated performances. TADIRs fist prototype was demonstrated at the beginning of 1998 and is currently under evaluation.
A 9.3 micrometer cutoff 320 X 256 quantum well infrared photodetector (QWIP) based thermal camera has been demonstrated as a laboratory set-up configuration. The development of the QWIP arrays and system integration is described. Performance analysis of systems which are based on QWIP arrays were performed to evaluate the potential of 320 X 256 and 640 X 480 QWIP array to be a candidate for future mid-end and high-end thermal imager.
As second generation FLIR systems become a reality the need for a reliable, high performance, moderately priced matrix arrays in the 8 - 12 micron atmospheric window becomes a real demand. At the same time, the remarkable advancement of QWIP technology over the past few years makes it one of the best candidates for such applications that suffice in the resolution provided by 320 by 256 pixel arrays. According to its fast advancement it could be expected that in the near future also the requirements of high-end applications will be met by QWIP technology. In light of this potential, the QWIP program in EL-OP was recently started in order to develop in- house QWIP technology and demonstrate 320 by 256 pixel image. Additionally we take part in scientific activities in a joint project with leading Israeli university groups. Preliminary results are presented, including the fabrication of QWIP arrays and measurement of single detectors. Measurement results show D* greater than 5 X 1010 Jones and responsivity approximately equals 0.5 A/W. Additionally, an optimization method for quasi-random scattering arrays is briefly presented.
'TADIR' is an El-Op's new second generation thermal imager based on 480 by 4 TDI MCT detector operated in the 8 - 10.5 micrometer spectral range. Although the prototype configuration design of TADIR is aimed toward the light weight low volume applications, TADIR is a generic modular technology of which the future El-Op second generation FLIR applications will be derived from. Beside the detector, what put the system in the second generation category are the state of the art features implemented in every component. This paper describes the system concept and design consideration have been taken during the development of its components.
We discuss the development and the performances of a very long wavelength (13.5 - 15 micrometer) 128 by 128 AlGaAs/GaAs multiquantum well infrared imaging system. A highly uniform, high-yield QWIP focal plane array was hybridized to a CMOS multiplexer operating in a direct injection mode. For efficient light coupling an integral random scattering reflector (random grating) was incorporated. Due to the high uniformity, excellent imagery, low noise as well as a noise equivalent temperature difference (NE(Delta) T) of less than 30 mK were obtained when operating around 45 K. Therefore, high image contrast signal to noise ratio has been achieved.
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