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Processes in the mind: perception, cognition, concepts, instincts, emotions, and higher cognitive abilities are considered here within a neural modeling fields paradigm. Its fundamental mathematical mechanism is a process "from vague-fuzzy to crisp", called dynamic logic. The paper discusses why this paradigm is necessary mathematically, and relates it to a psychological description of the mind. Cognitive algorithms using Dynamic Logic result in significant improvement of signal processing., The original document contains color images.

This report reviews the priorities and discusses cognitive algorithms resulting in breakthroughs in defense applications, and making progress toward achieving AF goals. The mathematical techniques of dynamic logic and neural modeling fields model aspects of the functionality of the mind: perception, cognition, and higher cognitive functions. This leads to a significant improvement in classical signal processing applications, including detection, tracking, and fusion in noise and clutter, making autonomous situational awareness possible. The first part of this report describes past difficulties, why these problems have not been solved for decades, and the gist of the current approaches. The second part of this report addresses future research directions: the augmentation of human performance through improvements in man-machine interfaces. This includes modeling of language interacting with cognition. In future systems, computers will learn from humans, and humans will operate machines by language and thoughts.., The original document contains color images.

Integrated optics today is based upon chips of Si and InP. The future of this chip industry is probably contained in the thrust towards optoelectronic integrated circuits (OEICs) and photonic integrated circuits (PICs) manufactured in a high-volume foundry. We believe that reconfigurable OEICs and PICs, known as ROEICs and RPICs, constitute the ultimate embodiment of integrated photonics. This paper shows that any ROEIC-on-a-chip can be decomposed into photonic modules, some of them fixed and some of them changeable in function. Reconfiguration is provided by electrical control signals to the electro-optical building blocks. We illustrate these modules in detail and discuss 3D ROEIC chips for the highest-performance signal processing. We present examples of our module theory for RPIC optical lattice filters already constructed, and we propose new ROEICs for directed optical logic, large-scale matrix switching, and 2D beamsteering of a phased-array microwave antenna. In general, large-scale-integrated ROEICs will enable significant applications in computing, quantum computing, communications, learning, imaging, telepresence, sensing, RF/microwave photonics, information storage, cryptography, and data mining., Published in Advances in OptoElectronics, v2011, article ID 627802, 2011.

We present a reconfigurable optical directed logic architecture that offers several significant improvements over the original directed logic presented by Hardy and Shamir. Specific embodiments of on-chip, waveguided, large-scale-integrated, cellular optical directed logic fabrics are proposed and analyzed. Five important logic functions are presented as examples to show that the same switch fabric can be reconfigured to perform different logic functions. Optical logic devices; (250.3140) Integrated optoelectronic circuits; (200.4660) Optical logic., Published in ACS-Nano, v5 n2 p1179-1189, 2011. Prepared in cooperation with Air Force Research Laboratory (AFRL), Hanscom AFB, MA. The original document contains color images.

The origin of the Log Law behavior of a wall-bounded turbulent boundary layer is outlined. The new theory of the origin of the Log Law starts with previous experimental observations that show that the turbulent boundary layer fluid undergoes rapid changes in the wall shear stress at any point on the wall. The main insight provided herein is that this rapid change in the wall shear stress corresponds to a rapid, quantifiable change in the location of the viscous sublayer toward and away from the wall in the velocity boundary layer. When this viscous layer is then spatially averaged, we theorize that the normal exponential-like decay of the viscous shear is stretched out in the tail region. The next step is to use various experimental results from the literature to show that the viscous sublayer, which is directly proportional to the second derivative of the velocity profile, extends much deeper into the boundary layer than previously thought. In fact it is shown that the viscosity effects extend all the way into the Log Law region where the spatially-averaged tail region begins to show a oneover- distance-from-the-wall-squared behavior. Hence, when the spatially-averaged second derivative profile is twice integrated to obtain the velocity profile perpendicular to the wall, one obtains the classic logarithmic profile behavior of the Log Law region of the turbulent boundary layer., The original document contains color images.

The parametric adaptive matched filter (PAMF) detector for space-time adaptive processing (STAP) detection is re-examined in this paper. Originally, the PAMF detector was introduced by using a multichannel autoregressive (AR) parametric model for the disturbance signal in STAP detection. While the parametric approach brings in benefits such as significantly reduced training and computational requirements as compared with fully adaptive STAP detectors, the PAMF detector as a reduced-dimensional solution remains unclear. This paper employs the conjugate-gradient (CG) algorithm to solve the linear prediction problem arising in the PAMF detector. It is shown that CG yields not only a new computationally efficient implementation of the PAMF detector, but it also offers new perspectives of PAMF as a reduced-rank subspace detector. The CG algorithm is first introduced to provide alternative implementations for the matched filter (MF) and parametric matched filter (PMF) when the covariance matrix of the disturbance signal is known. It is then extended to the adaptive case where the covariance matrix is estimated from training data. Important issues such as unknown model order and convergence rate are discussed. Performance of the proposed CG-PAMF detector is examined by using the KASSPER and other computer generated data., See also ADM002322. Presented at the 2010 IEEE International Radar Conference (9th) held in Arlington, VA on 10-14 May 2010. Published in the Proceedings of the 2010 IEEE International Radar Conference (9th), p740-745, 2010. Sponsored in part by the U.S. Navy.

This work proceeds from the paper we published in RadarCon 2009 titled "Multistatic scattering from moving targets in multipath environments", where we explored the potential to track moving ground targets with radar as they enter urban areas and become obscured by buildings. An X-band radar data collection was performed which validates the predicted multipath response, and the received multipath power in relation to the line-of-sight (LOS) response. Results from a bistatic experiment are used to examine the spatial coherency of energy reflecting from a large, rough surface, and the power distribution in angle that illuminates a target as it traverses in front of a building. This experiment may inspire knowledge-based methods to coherently process multipath returns, beyond that of standard GMTI processing, i.e., free-space matched-filtering (FFT) and CFAR detection., See also ADM002322. Presented at the 2010 IEEE International Radar Conference (9th) Held in Arlington, Virginia on 10-14 May 2010. Sponsored in part by DARPA. The original document contains color images.

The problem of theoretically describing forced laminar flow over a flat plate is revisited. For the last hundred years it has been assumed that the Blasius solution model applies to this case. However, upon close review it is found that the Blasius model has a serious problem in that the Blasius model assumes that the pressure gradient on the plate in the flow direction is zero. In fact what one expects is that a pressure gradient develops as fluid is displaced from the plate due to the developing boundary layer. Therefore, the Blasius model is not a valid physical model of the flow over a flat plate as depicted in most textbooks. In this report, we develop a more realistic Falkner-Skan type similar solution that closely matches the flow one would expect for flow over a flat plate. We replace the usual zero pressure gradient assumption with a nonzero pressure gradient assumption. The resulting solution for the velocity profile parallel to the plate results in a velocity profile that is very similar to the Blasius solution velocity profile. The big difference in the two models is in the velocity perpendicular to the plate. For the Blasius solution, this velocity results in a net outflow whereas the new model's velocity results in a net inflow. This net inflow is critical in that it allows one to use the flat plate as a model for a wing with aerodynamic lift., The original document contains color images.

In this work, we examine ground target detection and characterization from radar data, which incorporates a modelbased optimization method called dynamic logic (DL). We apply our methodology to a prototype airborne radar platform called Gotcha, developed by the Air Force Research Laboratory/Sensors Directorate/Automatic Target Recognition Division in recent years. The aircraft traces out a circular path around an area of interest, and the onboard, side-looking radar transmits and receives energy at a constant pulse repetition frequency, while the main beam direction is maintained at a fixed aim point on the ground. Data collected during any appropriate length arc of the flight path can be used to create synthetic aperture radar (SAR) images of the ground. The data can also be used for ground moving target indication (GMTI) and provide Doppler/Range imagery of the same ground area. Our approach combines the computation of Range-Doppler surfaces and a variable target velocity backprojection SAR method. Potential targets are detected using multiple backprojection images and features are extracted using adaptive mixture models. We demonstrate the feasibility of our approach using target truth information provided with the Gotcha dataset. We outline the steps toward implementing a comprehensive automatic target tracking solution based on presented methodology., See also ADM002322. Presented at the 2010 IEEE International Radar Conference (9th) Held in Arlington, Virginia on 10-14 May 2010. Sponsored in part by the Navy. The original document contains color images.

This paper presents an approach to detect people, or dismounts, using synthetic aperture radar (SAR). This approach is compared qualitatively with ground moving target indication (GMTI) radar and then quantitative results are presented using a P-band single phase center SAR. It is demonstrated that SAR provides an excellent methodology to detect dismounts., See also ADM002322. Presented at the IEEE International Radar Conference (9th), held in Arlington, VA on 10-14 May 2010. Sponsored in part by the Navy. The original document contains color images. Sponsored in part by AFOSR.

Multistatic radars utilize multiple transmitter and receiver sites to provide several different monostatic and bistatic channels of observation. Multistatic passive and active systems can offer many advantages in terms of coverage and accuracy in the estimation of target signal parameters but unfortunately their performances are heavily sensitive to the position of receivers (RX) and transmitters (TX) with respect to the target trajectory. As known, geometry factors play an important role in the shape of the ambiguity function (AF) which is often used to measure the possible global resolution and large error properties of the target parameters estimates. Exploiting the relation between the ambiguity function and the Cramer-Rao lower bound (CRLB), in this work we propose an algorithm for choosing in a multistatic scenario, along the trajectory of the tracked target, the pair TX-RX with the best asymptotic performance calculated in terms of CRLB on estimation accuracy., See also ADM002322. Presented at the 2010 IEEE International Radar Conference (9th) Held in Arlington, Virginia on 10-14 May 2010. Sponsored in part by the Navy. The original document contains color images.

An analytic perturbation solution is developed for a single cell SQUID and for multi-cell rows with random cell sizes (constrained by having a mirror symmetry about the center junction). The response of a single SQUID to an external RF signal is determined in terms of correlation functions between the phase of the inline effective junction and the circulating current. This yields an RF phase shift that can be calculated as a function of the circuit parameters and the signal frequency. Summing the phase shifted RF voltages of many random cell size SQUIDs in series yields the SQIF RF response., The original document contains color images.

We developed a cognitively inspired mathematical learning framework called Neural Modeling Fields (NMF). We applied it to learning and to recognition of situation composed of objects. NMF can successfully overcome the combinatorial complexity of associating subsets of objects with situations and provides fast and reliable convergence. We discuss the implications of the results of this current work for building multi layered intelligent systems., The original document contains color images.

Multistatic radars utilize multiple transmitter and receiver sites to provide several different monostatic and bistatic channels of observation. Multistatic passive and active radar systems can offer many advantages in terms of coverage and accuracy in the estimation of target signal parameters. Unfortunately, their performances are heavily sensitive to the position of receivers and transmitters with respect to the position of the target. It is well know that geometry factors play an important role in the shape of the ambiguity function (AF) which is often used to measure the possible global resolution and large error properties of the target parameters estimates. In this work we exploit the relation between the ambiguity function and the Cramer-Rao lower bound (CRLB) to calculate the bistatic CRLBs of target range and velocity and so obtaining a local measure of the estimation a ccuracy of these parameters. We also propose an algorithm for choosing in a multistatic scenario, along the trajectory of the tracked target, the pair transmitter-receiver with the best asymptotic performance calculated in terms of CRLB on estimation accuracy., The original document contains color images.

New similarity criteria are obtained for the velocity profile and the Reynolds stress terms by a stream function approach using the transformed x-momentum balance equation and the transformed Reynolds stress transport equation. The similarity criteria are similar to earlier results but are developed without a priori assumptions as to the velocity or Reynolds stress term scaling variables. Using the criteria, eleven experimental datasets for turbulent flow on a wedge are found. Scaling results indicate that the displacement thickness, the momentum thickness, the ninety-nine percent thickness, and the Rota-Clauser thickness all work as the outer region similarity thickness scale. The experimental and theoretical evidence indicates the free stream velocity works well as the velocity scaling parameter. For the Reynolds stress scaling. experimental evidence is for the most part ambiguous. However. recent DNS results clearly indicate that the friction velocity squared is the proper scaling but this result is seemingly at odds with the new theoretical criteria. Resolution of the conflict is made by the observation that similarity?like behavior of the velocity profile and the Reynolds stress terms are only obtained for the flow datasets where the ratio of the free stream velocity to the friction velocity is almost constant.

For the first time it is shown that the Prandtl length scale has a natural interpretation in terms of the physical structure of the boundary layer for a 2-0 wall bounded flow. Both the Prandtl length scale and a newly developed parameter are first moments associated with the mean location value of the second derivative of the velocity profile. These two parameters therefore track the mean location of the viscous forces present in the boundary layer. A simple mathematical proof is offered to show that the new parameter must be a similarity scaling parameter for all 2-0 boundary layer flows. From the parameter definitions, one can show that the new scaling parameter is identical to the Prandtl parameter scaling for the case where the ratio of the free stream velocity at the boundary layer edge to the Prandtl scaling velocity, the so called friction velocity, is a constant. This similarity condition is found in certain turbulent boundary layer flow data sets. We show that to experimental accuracy, a subset of these datasets exhibit whole profile similarity using the new scaling parameters if one assumes that the reported skin friction coefficients are in error by +-10%. The results lead to a new conceptual picture for similarity of the turbulent boundary layer.

Nonlinear information processing via two-beam coupling using thin-film organic photorefractive material is demonstrated. The organic material is found to possess superior response time and resolution compared to photorefractive bulk material. The possibility of designing dynamic range compression deconvolution for restoring blurred images embedded in a noisy environment is also demonstrated, In-house contract. Prepared in collaboration with Solid State Scientific Corporation, Hollis, NH; and University of Arizona, Tucson, AZ. Presented at the SPIE Optical Pattern Recognition Conference (20th) held in Orlando FL on 13-17 April 2009. Published in the Proceedings of the SPIE Optical Pattern Recognition Conference (20th), v7340 n73400J p1-15, 2009.

A new near-wall approximate analytical velocity profile is developed for wall-bounded turbulent boundary layers in an adverse pressure gradient. The new velocity profile approximation is used to fit experimental profile data in order to extract near-wall information such as the skin friction coefficient and the viscous layer thickness. Results with Direct Numerical Simulation computer generated data shows the method works well and is superior to the existing model from the literature. Fits to experimental wind tunnel APG data sets indicate that the new analytical velocity profile works well., In-house contract. The original document contains color images.

The TechSat21 space-based radar concept, suggested by AFRUVS, employs a cluster of free-floating satellites, each of which transmits its own orthogonal signal and receives all reflected signals. The satellites operate coherently at X-band. The cluster forms essentially a multi-element interferometer with a concomitant large number of grating lobes and significant ground clutter. This study explores some basic characteristics of such a system with respect to detection of slowly-moving ground targets (GMTI)., The original document contains color images.

This report documents basic research in electromagnetic components performed by members of the Antenna Technology Branch of the Air Force Research Laboratory in collaboration with on-site contractors. The work includes modeling and measurement of III-V compound semiconductor devices for microwave and millimeter-wave transmit and receive applications, investigations of the factors that limit lifetime of radio frequency micro-electro-mechanical switches, creation of new micro-electro-mechanical and micromachined electromagnetic components, and investigation of the potential of emerging material systems for application to components. The research was supported by the Air Force Office of Scientific Research under Laboratory Tasks 92SN04COR and 07RY06COR., The original document contains color images.

A new approach is described for combining range and Doppler data from multiple radar platforms to perform multi-target detection and tracking. In particular, azimuthal measurements are assumed to be either coarse or unavailable, so that multiple sensors are required to triangulate target tracks using range and Doppler measurements only. Increasing the number of sensors can cause data association by conventional means to become impractical due to combinatorial complexity, i.e., an exponential increase in the number of mappings between signatures and target models. In the new approach, the data association is performed probabilistically, using a variation of expectation-maximization (EM). Combinatorial complexity is avoided by performing an efficient optimization in the space of all target tracks and mappings between tracks and data. The full, multi-sensor, version of the algorithm is tested on simulated data. The results demonstrate that accurate tracks can be estimated by exploiting spatial diversity in the sensor locations. These results are promising, and demonstrate robustness in the presence of nonhomogeneous clutter., Published in the Journal of IEEE Transactions on Aerospace and Electronic Systems v45 n2 April 2009.

The radiative transfer (RT) approach is widely used for studying scattering from layered random media with rough interfaces. Although it has been successful in several applications such as remote sensing of atmosphere it is well known that this approach involves certain approximations. In this paper these assumptions and approximations are reexamined and explained. To enable this a statistical approach is employed to this problem and the governing equations for the first and second moments of the wave fields are derived. A transition is hence made to arrive at a system of equations corresponding to that of the RT approach. It is thus found that more conditions are implicitly involved in the RT approach than generally believed to be necessary., Published in Atmospheric Propagation of Electromagnetic Waves III, Proceedings of the SPIE, v7200 p720007-1 through 720007-12, 2009.

New results for similarity scaling of the velocity profile of the 2-D wall-bounded flows are presented. The theoretical results are based on a simple concept; the area under similar scaled velocity profile curves must be equal. By taking certain integrals of the scaled velocity profiles and its first derivative, we obtain a number of similarity scaling requirements. For example, it is shown that if whole profile similarity exists, then: 1) the similar length scaling variable must be proportional to the displacement thickness, and 2) the velocity similarity scaling variable must be proportional to the free-stream velocity. Conventional thinking is that whole profile similarity is limited to laminar flow boundary layers. If true, this would drastically restrict the utility of the new scaling results. However, we show that to experimental accuracy, certain turbulent boundary layer flow datasets can display whole profile similarity and that as predicted the new scaling works well. In addition, we develop new definitions for partial similarity for the inner, the outer, and the log law regions of a turbulent boundary layer. These definitions are most suitable for quantifying similarity of experimental profiles.

In this report a new method for describing the shape and thickness of 2-D wall bounded boundary layer velocity profiles is presented. The new method is based on calculating parameters using simple integrals of the velocity profile. It is shown that these new parameters can be used to describe both the inner and outer region of the turbulent boundary layer, as well as laminar and transitional velocity profiles. Applied to experimental laminar-turbulent profiles, it is shown that one of the new shape parameters foretells the beginning of the laminar turbulent transition on a flat plate at a much lower Reynolds number than the traditional H12 criteria. Furthermore, using another new parameter it is shown that the transition to fully turbulent flow may proceed as a discontinuous event.

Plasmon resonances in the two dimensional electron gas (2-deg) of a high electron mobility transistor (HEMT) can affect transport properties. The resonance frequency depends on the gate-tuned sheet charge density of the 2-deg and on the characteristic length of the gate metallization by which free space THz radiation couples to the plasmon. Thus, this type of device can be used as a tunable detector. This work presents an experimental investigation of such a device fabricated from the InGaAs/InP material system. E-beam lithography was used to fabricate a gate in the form of a grating with submicron period. Sensitivity of the conductance to incident THz fields is reported. Direct absorption of THz, temperature effects, and the effects of source to drain current on system performance are also investigated. It is expected that this class of device will find use in space-borne remote sensing applications., Published in the proceedings of the SPIE, Infrared Spaceborne Remote Sensing and Instrumentation XVI, v7082 p70820B-1 through 70820B-8, 2008. Prepared in collaboration with University of Central Florida, Orlando, FL, and Solid State Scientific Corporation, Nashua, NH. Sponsored in part by Air Force Office of Scientific Research (AFOSR).

Low-pressure hydride vapor phase epitaxy (HVPE) is being used for the regrowth of thick GaAs on orientation-patterned templates for nonlinear optical frequency conversion. We have achieved epitaxial growth rates of 200um/h and produced millimeter-thick films in 10-h-long growth runs. A critical problem in the HVPE regrowth of orientation-patterned GaAs is the preservation of the original patterned structure - during thick growth, the domain walls often bend and annihilate. Measurements indicated that the domain wall bending decreased as the growth temperature was reduced. The substrate miscut and the orientation of unpatterned regions also affect the vertical propagation of domain walls. In this paper we discuss the process improvements which have facilitated the production of millimeter-thick layers with nearly vertical domain walls., Prepared in collaboration with the Solid State Photonics Laboratory and the E. L. Ginzton Laboratory, both of Stanford University, Stanford, CA. Published in Journal of Crystal Growth v310 n24 p5241-5247, Dec 2008; available online 30 Aug 2008.

The fabrication of thick orientation-patterned GaAs (OP-GaAs) films is reported using a two-step process where an OP-GaAs template with the desired crystal domain pattern was prepared by wafer fusion bonding and then a thick film was grown over the template by low pressure hydride vapor phase epitaxy (HVPE). The OP template was fabricated using molecular beam epitaxy (MBE) followed by thermocompression wafer fusion, substrate removal, and lithographic patterning. On-axis (100) GaAs substrates were utilized for fabricating the template. An approximately 350 micrometers thick OP-GaAs film was grown on the template at an average rate of ~70 micrometers/hr by HVPE. The antiphase domain boundaries were observed to propagate vertically and with no defects visible by Nomarski microscopy in stain-etched cross sections. The optical loss at ~2 micrometers wavelength over an 8 mm long OP-GaAs grating was measured to be no more than that of the semi-insulating GaAs substrate. This template fabrication process can provide more flexibility in arranging the orientation of the crystal domains compared to the Ge growth process and is scalable to quasi-phase-matching (QPM) devices operating from the IR to terahertz frequencies utilizing existing industrial foundries., Prepared in collaboration with Photonics Center, University of Massachusetts, Lowell, MA, and Physical Sciences, Inc., Andover, MA. Published in Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications 7, Proceedings of the SPIE, v6875, paper 68750H, 2008. Sponsored in part by Air Force contract no. FA9550-06-C-0053.

We apply the "effective mode volume" theory to evaluate enhancement of the electroluminescence efficiency of semiconductor emitters placed in the vicinity of isolated metal nanoparticles and their arrays. Using the example of an InGaN/GaN quantum-well active region positioned in close proximity to Ag nanospheres, we show that while the enhancement due to isolated metal nanoparticles is large, only modest enhancement can be obtained with ordered array of those particles. We further conclude that random assembly of isolated particles holds an advantage over the ordered arrays for light emitting devices of finite area., The original document contains color images. Published in Applied Physics Letters, v93 p021120-1 through 021120-3, 2008.

We fabricated and tested our previously designed optical correction element with zoom capability to convert nonlinear sinusoidal scans into linear scans. The design methodology is based on derivating a graded index of refraction device as a reference design and converting the graded index of refraction into an amplitude or phase binarized diffractive element. Our graded index of refraction derivation is based on the propagation of an electromagnetic wave in an inhomogeneous media. Our experimental results showed the first order diffraction linearization of the sinusoidal scanning which is in agreement with our theory. The second order linearization was also discovered experimentally which was not predicted by the theory. The tests of the diffractive element device indicate that the linearization has small errors., Submitted for publication in the journal Applied Optics. Prepared in collaboration with Solid State Scientific Corporation, Hollis, NH. Sponsored in part by Air Force Office of Scientific Research (AFOSR). The original document contains color images.

We propose a new approach for designing diffractive optical corrective elements with zooming capability to convert nonlinear sinusoidal scanning into linear scanning. Such devices will be useful for linearizing the angular scan of a resonant mirror scanner. The design methodology is to create a graded index of refraction device as the reference design, with its index of refraction parameters based on beam retardation through propagation in an inhomogeneous media. In a new approach, we make explicit use of the symmetry of the optical problem to mathematically derive the form of the refractive gradient. The diffractive element is designed utilizing a binarizing algorithm of the accumulated phase from transmission through the refractive element., Submitted for publication in the journal Applied Optics. Prepared in collaboration with Solid State Scientific Corporation, Hollis, NH. The original document contains color images.

In this paper the A-law/Mu-law Dynamic Range Compression algorithm used in telecommunication systems is proposed for the first time for nonlinear Dynamic Range Compression image restoration of blurred signals embedded in very high noise environment. Our simulation results demonstrate that the dynamic range compression image deconvolution via the A-law/Mu-law outperforms image restoration based on the well-established image restoration filters that have been used for the last fifty years such as Wiener filter and Inverse filter. The deconvolution orders have been analyzed using the nonlinear transform method., Submitted for publication in the journal Applied Optics. Prepared in collaboration with Solid State Scientific Corporation, Hollis, NH, and University of Massachusetts, Lowell, MA. The original document contains color images.

ZnO is a wide bandgap semiconductor with very promising expectation for UV optoelectronics. The existence of large crystals should allow homoepitaxial growth of ZnO films for advanced optoelectronic devices. However, the ZnO substrates are not yet mature. Both defect induced by growth and by polishing together with the high reactivity of the surface are problems to their industrial application. Cathodoluminescence (CL) was used to probe the quality of substrates from two different suppliers. The surface damage was studied by varying the penetration depth of the electron beam, allowing to observe significant differences between the two samples within a 0.5-mm-thick surface layer. CL spectra show a complex band (P1) at _3.3 eV composed of two overlapped bands (3.31 and 3.29 eV) related to point defects (PD) and the 1-LO phonon replica of the free exciton (FX-1LO). This band (P1) is shown to be very sensitive to the presence of defects and the surface and thermal treatments. Its intensity compared with the excitonic band intensity is demonstrated to provide criteria about the quality of the substrates., Prepared in collaboration with the Fisica de la Materia Condensada, Valladolid, Spain; the Tecnologia Electronica, Universidad Politecnica de Madrid, Madrid, Spain; the Solid State Scientific Corporation, Hollis, NH; and Dpto. Matematicas y Fisica, UniNorte, Barranquilla, Colombia. Published in Journal of Crystal Growth, v310 p1000-1005, Nov 2007.

The realization of plasmo-electronic integrated circuits in a silicon chip will be enabled by two new plasmonic materials that are proposed and modeled in this article. The first is ion-implanted Si (n-type or p-type) at the surface of an intrinsic Si chip. The second is a thin-layer silicide such as Pd2Si, NiSi, PtSi2 WSi2 or CoSi2 formed at the Si chip surface. For doping concentrations of 1020 cm-3 and 1021 cm-3, our dispersion calculations show that bound surface plasmon polaritons will propagate with low loss on stripe-shaped plasmonic waveguides over the 10 to 55 um and 2.8 to 15 um wavelength ranges, respectively. For Pd2Si/Si plasmonic waveguides, the wavelength range of 0.5 to 7.5 um is useful and here the propagation lengths are 1 to 2300 um. For both doped and silicided guides, does into the conductive stripe material., The original document contains color images. Published in the Journal of Optics Express, v16, n9, 2008.

The gain of an antenna is usually measured by placing a transmitting antenna in the far field of the antenna under test (AUT) and then comparing the power received by that antenna with that received by a reference antenna (RA). Rather than having a separate power source for the transmitter, it is convenient to utilize the two ports of a Hewlett-Packard 8510C Network Analyzer for the gain measurement. There are however some obstacles that arise when using this approach, particularly if the AUT has low gain and is to be measured over a wide frequency band. In order to overcome the above limitations we investigated an approach where the transmit antenna is a resonant monopole which is mounted on the same ground plane as the AUT and RA, which is also a resonant monopole. The resonant frequency of each monopole can be easily changed by using a telescoping arrangement. We review the theory and then present simulations and measurements when both transmitting and receiving antennas are mounted on a 4-ft x 4?ft (1.22 m x 1.22m) ground plane for the frequency range from 200 MHz to 1000 MHz. The agreement between theory, simulations and measurements is very good., The original document contains color images. Prepared in collaboration with ARCON Corp., Waltham, MA. Sponsored in part by Air Force Office of Scientific Research (AFOSR).

We describe the design of a silicon-based source for radiation in the 0.5-14 THz regime. This new class of devices will permit continuously tunable, milliwatt scale, cw, room temperature operation, a substantial advance over currently available technologies. Our silicon terahertz generator consists of a silicon waveguide for near-infrared radiation, contained within a metal waveguide for terahertz radiation. A nonlinear polymer cladding permits two near-infrared lasers to mix, and through difference-frequency generation produces terahertz output. The small dimensions of the design greatly increase the optical fields, enhancing the nonlinear effect. The design can also be used to detect terahertz radiation., Published in Jnl. Optical Society of America, v25 n2 p261-268, Feb 2008.

Over the last few years we have been analyzing state-of-the-art spectral /temporal data of many events. Our goal was to develop specific techniques to classify and identify events based on these measurements. While the techniques evolved from one data type, we focus in this paper on the technique itself and its potential efficacy when applied to other data types. We use a Singular Value Decomposition (SVD) technique to cluster like events by forming a scatter plot from the first two eigenvectors. An evaluation of this approach using real data as well as simulations is given. A novel technique is introduced to assess cluster stability in the absence of ground truth. Results are presented along with the effects of misalignment of data samples, compression, training sets, and classifiers. The overall methodology is quite powerful and has remarkable noise immunity., Prepared in collaboration with Solid State Scientific Corporation, Hollis, NH.

We propose using the smart antenna principle as the basis of a new design for smart optical receivers in LADAR systems. This paper demonstrates the feasibility of designing a LADAR system with a receiver consisting of an array of photodetectors, which leads to field-of-view enhancement and beamforming by fusing streams of video information received from the detectors. As a proof of concept, we demonstrate this design by fusing several video information streams from different fields of view using our Mathworks Simulink model. The fusion algorithm uses the fuzzy logic maximum operation on the data output from the cameras., Presented at the Conference on Multisensor, Multisource Information Fusion: Architectures, Algorithms, and Applications, 16-20 Mar 2008. Published in the Proceedings of the SPIE, v6974 p69740H-1 through 69740H-7, 2008. Prepared in collaboration with Solid State Scientific Corporation, Hollis, NH.

Ultra-small silicon-based photonic-crystal ring resonators (PCRRs), both passive and active, will be key contributors to the emerging low-power nanophotonic technology. We have modeled and simulated the diameter-dependent loss, Q, and FSR of such PCRRs and find a 0.02 dB "intrinsic" loss that is independent of diameter, unlike the ~1/D loss of micro-strip resonators. Close to 100% drop efficiency at the drop channel of 1557.5nm was obtained by design with a high spectral selectivity of Q greater than 1319 in the single-ring PCRR-based add-drop filters with ring radius of 1.2 m. Ultra-compact polymer modulators were proposed and simulated, based on the hybrid integration of functional polymer materials with Si based PCRRs, which can lead to high speed modulators, suitable for photonic integration and RF photonics., Published in the Proceedings of the SPIE, v6896, 12 Feb 2008. Prepared in collaboration with University of Texas, Arlington, TX, and University of Wisconsin, Madison, WI. Sponsored in part by Air Force Office of Scientific Research (AFOSR).

The vision of longwave silicon photonics articulated in the Journal of Optics A, vol. 8, pp 840-848, 2006 has now come into sharper focus. There is evidence that newly designed silicon-based optoelectronic circuits will operate at any wavelength within the wide 1.6 to 200 micrometers range. Approaches to that LWIR operation are reviewed here. A long-range goal is to manufacture LWIR OEIC chips in a silicon foundry by integrating photonics on-chip with CMOS, bipolar, or BiCMOS micro-electronics. A principal LWIR application now emerging is the sensing of chemical and biological agents with an OE laboratory-on-a-chip. Regarding on-chip IR sources, the hybrid evanescent-wave integration of III-V interband-cascade lasers and quantum-cascade lasers on silicon (or Ge/Si) waveguides is a promising technique, although an alternative all-group-IV solution is presently taking shape in the form of silicon-based Ge/SiGeSn band-to-band and inter-subband lasers. There is plenty of room for creativity in developing a complete suite of LWIR components. Materials modification, device innovation, and scaling of waveguide dimensions are needed to implement microphotonic, plasmonic and photonic-crystal LWIR devices, both active and passive. Such innovation will likely lead to significant LIO applications, Published in SPIE Photonics West, Invited Paper 6898-5, Silicon Photonics III, 21 January 2008.. Pub. in the Journal of Optics A, v8, pp 840-848, 2006.

Adaptive waveform design for radar clutter cancellation requires knowledge of the rank of the clutter subspace. In this paper, we compare the computed clutter subspace rank, r, using three methods: (i) the exponentially embedded family (EEF) estimator, (ii) Rissanen's minimum description length (MDL) estimator, and (iii) the statistical ranking and selection method (CWA)., Published in Waveform Diversity and Design, p339-343, 2007.

We report results of a surface modification process for (100) GaSb using gas cluster ion beams(GCIB) that removes chemical mechanical polish (CMP) induced surface damage and replaces the native oxide with an engineered surface oxide, the composition of which depends on the reactive gas employed. X-ray photoelectron spectroscopy of O2-, CF4/O2-, and HBr-GCIB surface oxides is presented indicating the presence of mixed Ga- and Sb-oxides, with mostly Ga-oxides at the interface, desorbing at temperatures ranging 530 degrees C to 560 degrees C. Cross-sectional transmission electron microscopy of molecular beam epitaxy grown GaSb/AlGaSb layers showed that the HBr-GCIB surface produced a smooth dislocation-free substrate-to-epi transition with no discernable interface. Topography of epi surfaces, using atomic force microscopy, showed that GCIB surfaces resulted in characteristic step-terrace formations comprising monatomic steps and wide terraces. The HBr-GCIB process can be easily adapted to a large scale manufacturing process to produce epi-ready GaSb substrates., Published in the Jnl. of Crystal Growth 310, p1619-1626, 2008.

A novel spectral imaging sensor based on dual direct vision prisms is described. The prisms project a spectral image onto the focal plane array of an infrared camera. The prism set is rotated on the camera axis and the resulting spectral information is extracted as an image cube(x, y, 1), using tomographic techniques. The sensor resolves more than 40 spectral bands (channels) at wavelengths between 1.2 microns and 2.5 microns wavelength. The sensor dispersion characteristic is determined by the vector sum of the dispersions of the two prisms. The number of resolved channels, and the related signal strength per channel, varies with the angle between the prism dispersion axes. This is a new capability for this class of spectral imaging sensor. Reconstructed short-wave imagery and spectral data is presented for outdoor and laboratory scenes and for standard test sources., Published in the Proceedings of SPIE v6660 6660J.

We report here far infrared photonic crystals comprised of a lattice-matched pair of semiconductor materials: GaP and Si, or GaAs and Ge, or AlAs and GaAs. The crystals operate in a wavelength range where the real refractive index of one material undergoes a major dispersion associated with the LO and TO phonon absorption peaks. Using electromagnetic theory, we investigated the photonic-bandgap response for both TE and TM polarizations. Propagation losses for two types of crystals are estimated in this paper. These structures offer promise for the integration of III-V materials (GaP, GaAs) on group IV (Si, or Ge) for practical, active, far infrared photonic devices, such as light sources, amplifiers, modulators, reconfigurable waveguides and switches., Published in Optics Express, v15 n17 p10637-10648, 20 August 2007. Prepared in collaboration with University of Texas, Arlington, TX. The original document contains color images.

We present a Raman scattering study of wurtzite ZnO over a temperature range from 80 to 750 K. Second order Raman features are interpreted in the light of recent ab initio phonon density of states calculations. The temperature dependence of the Raman intensities allows the assignment of difference modes to be made unambiguously. Some weak, sharp Raman peaks are detected whose temperature dependence suggests they may be due to impurity modes. High-resolution spectra of the E2 high, A1(LO), and E1(LO) modes were recorded, and an analysis of the anharmonicity and lifetimes of these phonons is carried out. The E2 high mode displays a visibly asymmetric line shape. This can be attributed to anharmonic interaction with transverse and longitudinal acoustic phonon combinations in the vicinity of the K point, where the two-phonon density of states displays a sharp edge around the E2 high frequency. The temperature dependence of the linewidth and frequency of the E2 high mode is well described by a perturbation-theory renormalization of the harmonic E2 high frequency resulting from the interaction with the acoustic two-phonon density of states. In contrast, the A1(LO) and E1(LO) frequencies lie in a region of nearly flat two-phonon density of states, and they exhibit a nearly symmetric Lorentzian line shape with a temperature dependence that is well accounted for by a dominating asymmetric decay channel.

We recently reported the CVD growth of binary Ge(1-y)Sn(y) and ternary Ge(1-y)Si(x)Sn(y) alloys directly on Si wafers using SnD(4), Ge(2)H(6) (di-germane), SiH(3)GeH(3), and (GeH(3))(2)SiH(2) sources. Ge(y)Sn(y) is an intriguing infrared material that undergoes an indirect-to-direct bandgap transition for y < 0.1. In addition, we have found that Ge(1-y)Sn(y) layers have ideal properties as templates for the subsequent deposition of other semiconductors: (a) they are strain-relaxed and have low threading-defect densities (105 cm-2) even for films thinner than 1 micrometer; (b) their low growth temperatures between 250 deg C and 350 deg C are compatible with selective growth, and the films possess the necessary thermal stability for conventional semiconductor processing (up to 750 deg C depending on composition); (c) they exhibit tunable lattice constants between 5.65 A and at least 5.8 A matching InGaAs and related III-V systems; (d) their surfaces are extremely flat; (e) they grow selectively on Si and not on SiO(2); and (f) the film surface can be prepared by simple chemical cleaning for subsequent ex-situ epitaxy., Published in Journal of Materials Research, v22 p3281-3291, Dec 2007. Prepared in collaboration with Arizona State University, Tempe, AZ. Sponsored in part by National Science Foundation (NSF). The original document contains color images.

This paper reviews recent world-wide progress in silicon-based photonics-and optoelectronics in order to provide a context for the papers in this special section of the IEICE Transactions. The impact of present and potential applications is discussed., Pub. in IEICE Trans. Electronics, vE91-C, n2 p129-130, 2 Feb 2008.

The basic two cell qubit contains four josephson junctions, two residing on the conductor common to the two cell loops, and one on each loop's perimeter. In the limit of zero inductance the qubit potential is described by two phase variables and two orthogonal external magnetic flux parameters (the symmetric and anti symmetric combinations of external flux). The barrier height of the effective double well potential is controlled by the symmetric external flux and the potential tilt by the anti symmetric flux. We will discuss the effect of non-zero inductance and defects on the qubit energy levels, circulating currents, matrix elements, and on the relaxation and phase decoherence times., The original document contains color images. Presented at the Conference of Frontiers of Josephson Physics and Nanoscience 2007, held in Palinuro, Italy, on 25-28 Sep 2007. Contains Briefing charts.

This paper surveys the current state of the art of digital beamforming (DBF) with an emphasis on current capabilities and practical implementation techniques. Digital control of phased arrays in both receive and transmit modes will be covered, including such key issues as hardware, integration, processing load, and cost. The viability of future trends in DBF will be examined in terms of feasibility and cost of the enabling technologies of adaptive hardware and embedded software., The original document contains color images. Presented at the Antenna Applications Symposium held in Monticello, IL on 17-20 Sep 2007.

In this paper, the Cramer-Rao inequality is applied to the likelihood function of the synthetic aperture radar (SAR) scatterer parameter vector to relate the choice of flight path to estimation performance. Estimation error bounds for the scatterer parameter vector (including height) are developed for multi-dimensional synthetic apertures. These bounds quantify the performance enhancement over a limited sector of the image plane relative to standard-aperture single-pass SAR missions. An efficient means for the design and analysis of SAR waveforms and flight paths is proposed using simulated scattering models that are limited in size. Comparison of the error bounds to those for standard-aperture SAR show that estimates of scatterer range and cross-range positions are accurate for multi-dimensional aperture SAR, even with the additional estimator for height. Furthermore, multi-dimensional SAR is shown to address the layover problem., Pub. in IEEE Transactions on Aerospace and Electronic Systems, v43 n1, p344-355, Jan 2007. ESC Clearance Number 05-0017. Prepared in cooperation with the Department of Electrical and Computer Engineering, Northeastern University, Boston, MA, and Anteon Corporation, Hanscom AFB, MA.

Since the first demonstration of negative refractive index using nested or edge coupled split ring resonators and posts, various proposals have been made for improvement of the structures. Loss is an ongoing concern for these media at microwave frequencies and above. One alternate design uses broadside coupled split rings printed front to back on a substrate. This approach, which avoids bianisotropic effects of edge coupled rings, has been demonstrated successfully inside waveguide below cutoff. Our work here investigates the combination of similar broadside coupled rings (BCRs) with negative permittivity posts in a metamaterial prism, rather than the previous guided-wave medium. Free space measurement of negative refraction through a prism has become our standard for proof of negative index. Unlike rectangular wave guide, free space measurement also allows true transverse electromagnetic illumination. To observe the different effects of magnetic and electric coupling in the rings, two different orientations of the ring gap were used. One type has the gap aligned with the post and is symmetric about the electric field axis. The other has the gap turned 90 degrees from the post. The broadside coupled version of each orientation is measured and compared to a single ring version of the same dimensions and orientation for a total of four prisms., The original document contains color images. Published in the Proceedings of the IEEE International Symposium on Antennas and Propagation, held in Honolulu, Hi Jun 2007.