MassTech Collaborative has helped to make the Commonwealth of Massachusetts a beacon for advanced manufacturing. In partnership with the AIM Photonics manufacturing institute, MassTech has launched five Laboratories for Education and Application Prototypes (LEAPs) within academic institutions spread widely across Massachusetts, to develop a skilled workforce in integrated photonics. Hands-on and in-person workshops, bootcamps and laboratory courses are offered at these LEAPs to learners from academia, industry, and the government. The MA LEAP network stands as an excellent self-sustaining model for hands-on STEM education and workforce training for the rest of the country.
A modular laboratory curriculum with exercises for students and lesson plans for teachers is presented. Fundamentals of basic integrated photonic (IP) devices can be taught, first as a lecture-in-the-lab followed by “hands-on” laboratory measurements. This comprehensive curriculum utilizes data collected from the “AIM Photonics Institute PIC education chip” that was designed specifically for the purpose of education, and was fabricated at AIM SUNY Poly. Training using this modular curriculum will be performed through the AIM Photonics Academy network in New York (NY) and Massachusetts (MA), either as a full semester course or as a condensed boot-camp. A synergistic development and delivery of this curriculum will coherently leverage multiple resources across the network and can serve as a model for education and workforce development in other Manufacturing USA institutes, as well as for overseas partners.
Millimeter-wave and terahertz continuous-wave radar systems have been used to measure physiological signatures for
biometric applications and for a variety of non-destructive evaluation applications, such as the detection of defects in
materials. Sensing strategies for the simplest homodyne systems, such as a Michelson Interferometer, can be enhanced
by using Frequency Modulated Continuous Wave (FMCW) techniques. This allows multiple objects or surfaces to be
range resolved while monitoring the phase of the signal in a particular range bin. We will discuss the latest
developments in several studies aimed at demonstrating how FMCW techniques can enhance mmW/THz sensing
applications.
KEYWORDS: Imaging systems, Sensors, Signal to noise ratio, Performance modeling, Target detection, Signal attenuation, Contrast transfer function, Atmospheric modeling, Extremely high frequency, Backscatter
The U.S. Army Research Laboratory (ARL) has continued to develop and enhance a millimeter-wave (MMW) and submillimeter- wave (SMMW)/terahertz (THz)-band imaging system performance prediction and analysis tool for both the detection and identification of concealed weaponry, and for pilotage obstacle avoidance. The details of the MATLAB-based model which accounts for the effects of all critical sensor and display components, for the effects of atmospheric attenuation, concealment material attenuation, and active illumination, were reported on at the 2005 SPIE Europe Security and Defence Symposium (Brugge). An advanced version of the base model that accounts for both the dramatic impact that target and background orientation can have on target observability as related to specular and Lambertian reflections captured by an active-illumination-based imaging system, and for the impact of target and background thermal emission, was reported on at the 2007 SPIE Defense and Security Symposium (Orlando). Further development of this tool that includes a MODTRAN-based atmospheric attenuation calculator and advanced system architecture configuration inputs that allow for straightforward performance analysis of active or passive systems based on scanning (single- or line-array detector element(s)) or staring (focal-plane-array detector elements) imaging architectures was reported on at the 2011 SPIE Europe Security and Defence Symposium (Prague). This paper provides a comprehensive review of a newly enhanced MMW and SMMW/THz imaging system analysis and design tool that now includes an improved noise sub-model for more accurate and reliable performance predictions, the capability to account for postcapture image contrast enhancement, and the capability to account for concealment material backscatter with active-illumination- based systems. Present plans for additional expansion of the model’s predictive capabilities are also outlined.
Historically, spectroscopy has been a cumbersome endeavor due to the relatively large sizes (3ft – 100ft in length) of
modern spectroscopy systems. Taking advantage of the photoacoustic effect would allow for much smaller absorption
chambers since the photoacoustic (PA) effect is independent of the absorption path length. In order to detect the
photoacoustic waves being generated, a photoacoustic microphone would be required. This paper reports on the
fabrication efforts taken in order to create microelectromechanical systems (MEMS) cantilevers for the purpose of
sensing photoacoustic waves generated via terahertz (THz) radiation passing through a gaseous sample. The cantilevers
are first modeled through the use of the finite element modeling software, CoventorWare®. The cantilevers fabricated
with bulk micromachining processes and are 7x2x0.010mm on a silicon-on-insulator (SOI) wafer which acts as the
physical structure of the cantilever. The devices are released by etching through the wafer’s backside and etching
through the buried oxide with hydrofluoric acid. The cantilevers are placed in a test chamber and their vibration and
deflection are measured via a Michelson type interferometer that reflects a laser off a gold tip evaporated onto the tip of
the cantilever. The test chamber is machined from stainless steel and housed in a THz testing environment at Wright
State University. Fabricated devices have decreased residual stress and larger radii of curvatures by approximately 10X.
Real-time, stand-off sensing of human subjects to detect emotional state would be valuable in many defense, security and medical scenarios. We are developing a multimodal sensor platform that incorporates high-resolution electro-optical and mid-wave infrared (MWIR) cameras and a millimeter-wave radar system to identify individuals who are psychologically stressed. Recent experiments have aimed to: 1) assess responses to physical versus psychological stressors; 2) examine the impact of topical skin products on thermal signatures; and 3) evaluate the fidelity of vital signs extracted from thermal imagery and radar signatures. Registered image and sensor data were collected as subjects (n=32) performed mental and physical tasks. In each image, the face was segmented into 29 non-overlapping segments based on fiducial points automatically output by our facial feature tracker. Image features were defined that facilitated discrimination between psychological and physical stress states. To test the ability to intentionally mask thermal responses indicative of anxiety or fear, subjects applied one of four topical skin products to one half of their face before performing tasks. Finally, we evaluated the performance of two non-contact techniques to detect respiration and heart rate: chest displacement extracted from the radar signal and temperature fluctuations at the nose tip and regions near superficial arteries to detect respiration and heart rates, respectively, extracted from the MWIR imagery. Our results are very satisfactory: classification of physical versus psychological stressors is repeatedly greater than 90%, thermal masking was almost always ineffective, and accurate heart and respiration rates are detectable in both thermal and radar signatures.
It is shown that with appropriate multimode illumination and modulation strategies, it is possible to achieve the high sensitivity of active illumination, with the elimination of the need for "strategic" angular orientation of the target and to do so while minimizing the impact of coherent effects such as speckle. It is also shown that very modest terahertz (THz) power levels correspond to very high brightness temperatures, even when this power is divided among the many modes of large enclosures. We also consider how technical advances in the THz will continue to expand the scenarios of applicability for these approaches.
The U.S. Army Research Laboratory (ARL) and the U.S. Army Night Vision and Electronic Sensors Directorate
(NVESD) have developed a terahertz-band imaging system performance model/tool for detection and identification of
concealed weaponry. The details of the MATLAB-based model which accounts for the effects of all critical sensor and
display components, and for the effects of atmospheric attenuation, concealment material attenuation, and active
illumination, were reported on at the 2005 SPIE Europe Security & Defence Symposium (Brugge). An advanced
version of the base model that accounts for both the dramatic impact that target and background orientation can have on
target observability as related to specular and Lambertian reflections captured by an active-illumination-based imaging
system, and for the impact of target and background thermal emission, was reported on at the 2007 SPIE Defense and
Security Symposium (Orlando). This paper will provide a comprehensive review of an enhanced, user-friendly,
Windows-executable, terahertz-band imaging system performance analysis and design tool that now includes additional
features such as a MODTRAN-based atmospheric attenuation calculator and advanced system architecture
configuration inputs that allow for straightforward performance analysis of active or passive systems based on scanning
(single- or line-array detector element(s)) or staring (focal-plane-array detector elements) imaging architectures. This
newly enhanced THz imaging system design tool is an extension of the advanced THz imaging system performance
model that was developed under the Defense Advanced Research Project Agency's (DARPA) Terahertz Imaging
Focal-Plane Technology (TIFT) program. This paper will also provide example system component (active-illumination
source and detector) trade-study analyses using the new features of this user-friendly THz imaging system performance
analysis and design tool.
We will present the continued development of a
millimeter-wave/sub-THz radar system used to capture and assess
micro-Doppler signatures of humans. This system is being developed to remotely monitor respiration and heartbeat rates
at standoff distances of up to 100 meters. We will discuss the latest hardware and software developments and recent
studies of the performance of the system under a variety of conditions.
Millimeter-wave monolithic integrated circuit (MMIC) technology is now widely recognized as a key to many modern applications in safety and security, ranging from near and far-field imaging and sensing to non-invasive material inspection. In this paper, we apply our
state-of-the-art MMIC technology to the analysis of gaseous media by spectroscopic techniques. The paper presents recent developments of amplifying and frequency-translating MMICs based on metamorphic HEMT technology and their application to the spectroscopic analysis of the frequency range from 250 to 330 GHz, including the important absorption line of water around 321 GHz.
The full potential of terahertz imaging systems for nondestructive aerospace imaging applications has not been realized
due to the lack of data linking damage and defects to terahertz signatures coupled with the complexity of modeling the
signatures. Terahertz systems (0.1 - 2.0 THz) may be ideally suited for NDI applications because of the ability of THz
radiation to penetrate through substances commonly found on the surfaces of aircraft structures while maintaining the
optical resolution required to detect defects. We will discuss several systems that we have used to study the signatures of
a set of target samples with known defects.
Millimeter-wave and terahertz radar systems can play an important role in multimodal layered sensing systems targeted
at measuring both physiological and behavioral biometric data for security and medical applications. We will describe a
228 GHz heterodyne radar system that is capable of measuring respiration rates at standoff distances of up to 50 meters
and simultaneously measure respiration and heartbeat rates at a distance of 10 meters. We will discuss the latest
hardware and signal processing developments and a wide range of studies aimed at optimizing the performance of the
system under a variety of potential field applications.
In this paper, we will describe the development of a 228 GHz heterodyne radar system as a vital signs sensing monitor
that can remotely measure respiration and heart rates from distances of 1 to 50 meters. We will discuss the design of the
radar system along with several studies of its performance. The system includes the 228 GHz transmitter and heterodyne
receiver that are optically coupled to the same 6 inch optical mirror that is used to illuminate the subject under study.
Intermediate Frequency (IF) signal processing allows the system to track the phase of the reflected signal through I and
Q detection and phase unwrapping. The system monitors the displacement in real time, allowing various studies of its
performance to be made. We will review its successes by comparing the measured rates with a wireless health monitor
and also describe the challenges of the system.
The characteristics of continuous-wave millimeter-wave/terahertz radars make them candidates to remotely sense the
physiological parameters of individuals, such as respiration and heart rates. The characteristics of these radars include
transmission through the atmosphere and clothing, well-collimated beams, and sensitivity to small displacements. The
directional Doppler velocity can be used to measure the movement of a subject's chest wall due to respiration and the
more subtle motion of the body due to the cardiopulmonary system. We will present an overview of two systems that
have been developed along with representative data from each.
The U.S. Army Night Vision and Electronic Sensors Directorate (NVESD) and the U.S. Army Research Laboratory
(ARL) have developed a terahertz-band imaging system performance model for detection and identification of
concealed weaponry. The details of this MATLAB-based model which accounts for the effects of all critical sensor and
display components, and for the effects of atmospheric attenuation, concealment material attenuation, and active
illumination, were reported on at the 2005 SPIE Europe Security and Defence Symposium. The focus of this paper is to
report on recent advances to the base model which have been designed to more realistically account for the dramatic
impact that target and background orientation can have on target observability as related to specular and Lambertian
reflections captured by an active-illumination-based imaging system. The advanced terahertz-band imaging system
performance model now also accounts for target and background thermal emission, and has been recast into a user-friendly,
Windows-executable tool. This advanced THz model has been developed in support of the Defense Advanced
Research Project Agency's (DARPA) Terahertz Imaging Focal-Plane Technology (TIFT) program. This paper will
describe the advanced THz model and its new radiometric sub-model in detail, and provide modeling and experimental
results on target observability as a function of target and background orientation.
This paper describes the design and performance of the U.S. Army RDECOM CERDEC Night Vision and Electronic
Sensors Directorate's (NVESD), active 0.640-THz imaging testbed, developed in support of the Defense Advanced
Research Project Agency's (DARPA) Terahertz Imaging Focal-Plane Technology (TIFT) program. The laboratory
measurements and standoff images were acquired during the development of a NVESD and Army Research Laboratory
terahertz imaging performance model. The imaging testbed is based on a 12-inch-diameter Off-Axis Elliptical (OAE)
mirror designed with one focal length at 1 m and the other at 10 m. This paper will describe the design considerations of
the OAE-mirror, dual-capability, active imaging testbed, as well as measurement/imaging results used to further develop
the model.
Terahertz imaging sensors are being considered for providing a concealed weapon identification capability for military and security applications. In this paper the difficulty of this task is assessed in a systematic way. Using imaging systems operating at 640 GHz, high resolution imagery of possible concealed weapons has been collected. Information in this imagery is removed in a controlled and systematic way and then used in a human observer perception experiment. From the perception data, a calibration factor describing the overall difficulty of this task was derived. This calibration factor is used with a general model of human observer performance developed at the US Army Night Vision and Electronic Sensors Directorate to predict the task performance of observers using terahertz imaging sensors. Example performance calculations for a representative imaging sensor are shown.
We have developed several millimeter/submillimeter/terahertz systems to study active and passive imaging and associated phenomenology. For measuring the transmission and scattering properties of materials, we have developed a dual rotary stage scattering system with active illumination and a Fourier Transform spectrometer. For imaging studies, we have developed a system based on a 12-inch diameter raster-scanned mirror. By interchange of active sources and both heterodyne and bolometric detectors, this system can be used in a variety of active and passive configurations. The laboratory measurements are used as inputs for, and model calibration and validation of, a terahertz imaging system performance model used to evaluate different imaging modalities for concealed weapon identification. In this paper, we will present examples of transmission and scattering measurements for common clothing as well as active imaging results that used a 640 GHz source and receiver.
The U.S. Army Night Vision and Electronic Sensors Directorate and the U.S. Army Research Laboratory have developed a terahertz-band imaging system performance model for detection and identification of concealed weaponry. The MATLAB-based model accounts for the effects of all critical sensor and display components, and for the effects of atmospheric attenuation, concealment material attenuation, and active illumination. The model is based on recent U.S. Army NVESD sensor performance models that couple system design parameters to observer-sensor field performance using the acquire methodology for weapon identification performance predictions. This THz model has been developed in support of the Defense Advanced Research Project Agencies' Terahertz Imaging Focal-Plane-Array Technology (TIFT) program and is presently being used to guide the design and development of a 0.650 THz active/passive imaging system. This paper will describe the THz model in detail, provide and discuss initial modeling results for a prototype THz imaging system, and outline plans to validate and calibrate the model through human perception testing.
Important applications of the Terahertz/Submillimeter/Nearmillimeter/Millimeter/Far Infrared have been known for many years and a number of scientific laboratory and field instruments that approach fundamental limits have been developed. More recently, a number of 'public' applications for the non-specialist have been heavily promoted. In spite of this, no 'public' application has come to fruition and been widely adopted. With specific examples, we will show that advances in technology and scientific understanding are poised to change this. A particular emphasis will be placed on distinguishing between those opportunities for which there is a clear path to a 'public' application and those for which fundamentally unknown phenomenology or technological breakthroughs will be required.
There has been considerable interest in the use of the Submillimeter/THz (SMM/THz) spectral region for gas analysis and detection. This has been driven both by the importance of the application and the THz-TDS community. In this paper we will discuss and compare the attributes of an attractive alternative: cw submillimeter spectroscopy. Particular attention will be paid to sensitivity, specificity, and the investigations of harsh environments. A particularly simple system approach, the FAst Scan Submillimeter Spectroscopy Technique (FASSST), will be discussed and a compact and potentially very low cost implementation described. Results will be presented which include the analyses of complex mixtures of gases with absolute specificity.
The THz is unique among spectral regions because of the relative infancy of its commercial applications. Much of this infancy has been due to the well known difficulties of generating and detecting radiation. However, the enormous number of important applications in each of the other spectral regions has resulted at least as much from their large in-vestment in systems and applications development - an 'X' factor - as from the technological maturity of the spectral region. Examples in the radio region include magnetic resonance imaging (rf + 'X' = shaped magnetic fields, rf pulse sequences, and signal processing) and cruise missiles (rf = 'X' = rocket and guidance system). In the visible, Night Vision (light = 'X' = electron multiplication and fluorescence) serves as an example.
To grow to maturity, the THz needs not only to optimize its technology for native applications (imaging through ob-scuration, chemical sensing, etc.), but to integrate its attributes with other technologies to address a broader range of challenges. In this paper we will discuss the underlying physics of interactions in the THz to see how they lead to both the attractive and limiting features of the spectral region, while at the same time providing hints about how to overcome these limitations by considering 'X'. Specific examples of 'X' will be provided and the authors will welcome comments, suggestions, and ideas from the audience.
Terahertz imaging is becoming more viable for many applications due to advances in detector and emitter technologies. One of the applications for THz imaging is the detection and identification of concealed weapons (e.g., in airport security screening lines). The path described here provides an imaging performance model for the application of concealed weapon identification. The approach is the typical U.S. Army target acquisition model for sensor performance prediction coupled to the acquire methodology for weapon identification performance prediction.
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