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The cost of high sensitivity, high resolution, (640x480) Uncooled IR (UCIR) sensors is too high for the sensors to widely proliferate. To achieve cost reduction and production capacity goals, improvements are required in the following areas: the Read-out Integrated Circuit (ROIC), the pixel design, the Integrated Circuit Processing of MEMS structures, vacuum package design, batch assembly package processing and automated testing. The improvements result in increased yield at the wafer level, increased yield through packaging, lower labor assembly and testing costs and improved performance. A cost model will be presented to show the interrelationship of the various costs and how the reduction in cost may be achieved.

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024x1024 pixel quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NE(Delta)T) of 17 mK at a 95K operating temperature with f/2.5 optics at 300K background and the LWIR detector array has demonstrated a NE(Delta)T of 13 mK at a 70K operating temperature with the same optical and background conditions as the MWIR detector array after the subtraction of system noise. Both MWIR and LWIR focal planes have shown background limited performance (BLIP) at 90K and 70K operating-temperatures respectively, with similar optical and background conditions. In addition, we are in the process of developing MWIR and LWIR pixel collocated simultaneously readable dualband QWIP focal plane arrays.

Successful past experience of implementing long wave MCT 1st and 2nd Generation thermal imagers has demonstrated to THALES Optronics that MCT presents difficult challenges when correcting non-uniformity errors caused by rapidly changing detector element gain and offset drifts. These problems become even more demanding when the move is made from long linear arrays to focal plane arrays due to the significantly larger number of detector elements. Relaxation of these demands would make a significant impact on the price/performance trade which inevitably occurs in a camera development. In recognition of the need to offer UK MOD best value, THALES Optronics has initiated a programme to achieve a SXGA resolution camera and is working with UK MOD, over a two year period, to investigate whether an alternative technology can maintain the high resolution required whilst achieving a downward step change in price. The selected technology is 3rd Generation Gallium Arsenide long wave Quantum Well Infra-red Photodiode (QWIP) chosen because initial indications are that drift rates are orders of magnitude slower than MCT. The programme involves studies to determine effects of defect clusters, bimodalism, non-uniformity correction levels and higher than normal operating temperatures on achieving acceptable performance, including logistics, in user scenarios whilst maximising detector yield. Development of demonstrator IR camera hardware (technology readiness level 6/7) based on a THALES Research & Technology QWIP array is also part of the programme.

For preparing future military and industrial needs, SOFRADIR is working with CEA-LETI/LIR in the frame of DEFIR (Design of Excellence for the Future of InfraRed), on the third generation R&D mainly based on HgCdTe (MCT) material growth by Molecular Beam Epitaxy (MBE). Based on MCT grown by MBE, large wafers (4 inches and more) are available on Germanium in France and on Silicon in the USA. MBE process on alternative materials like Germanium, are in position to replace CZT homo-substrates and to compete with other material candidates. This enables very larger wafer size (4" and more) with a well-mastered thickness of the sensitive thin film deposition leading to very low cost 2D MCT arrays. In addition multi spectral arrays including advanced photodiode technologies are developed thanks to the MBE process. Therefore third generation IR detector studies in progress at DEFIR concern very large format sizes including small pixel pitch and high performance and mainly multi spectral and multi-color FPAs. New development results are presented and future trends are discussed.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A novel uncooled long-wave infrared imaging technology with optical readout is proposed and developed targeted for low cost thermal imaging applications. This technology uses the thermo-optic effect in a semiconductor to detect infrared signals rather than the thermal-resistance effect used in traditional microbolometers. The key component of the imager, the focal plane array, is made up of thermally tunable thin film filter membrane pixels. Each thermal pixel acts as a wavelength translator, converting far infrared radiation signals into near infrared signals which are then detectable by off-the-shelf CCD or CMOS cameras. This approach utilizes optical filter and MEMS technologies, to build a low-cost passive long wavelength infrared focal plane array without electrical leads or active cooling. Within one year since the commencement, NETD values of 0.28K in a 160x120 array operating at 22Hz video frame rate have been achieved without temperature control.

Raytheon Vision Systems (RVS) is developing two-color, large-format infrared FPAs to support the US Army’s Third Generation FLIR systems**. RVS has produced 640 x 480 two-color FPAs with a 20 P m pixel pitch. Work is also underway to demonstrate a 1280 x 720 two-color FPA in 2005. The FPA architecture has been designed to achieve nearly simultaneous temporal detection of the spectral bands while being producible for pixel dimensions as small as 20 microns. Raytheon’s approach employs a readout integrated circuit (ROIC) with Time Division Multiplexed Integration (TDMI). This ROIC is coupled to bias-selectable two-color detector array with a single contact per pixel. The two-color detector arrays are fabricated from MBE-grown HgCdTe triple layer heterojunction (TLHJ) wafers. The single indium bump design is producible for 20 P m unit cells and exploits mature fabrication processes that are in production at RVS for Second Generation FPAs. This combination allows for the high temporal and spatial color registration while providing a low-cost, highly producible and robust manufacturing process. High-quality MWIR/LWIR (M/L) 640 x 480 TDMI FPAs with have been produced and imaged from multiple fabrication lots. These FPAs have LWIR cutoffs ranging to 11 P m at 78K. These 20 P m pixel FPAs have demonstrated excellent sensitivity and pixel operabilities exceeding 99%. NETDs less than 25 mK at f/5 have been demonstrated for both bands operating simultaneously. Keywords: HgCdTe, infrared detectors, focal plane arrays, multi-spectral, two-color, 3

A 128(H) x 64(V) x RGB CMOS imager is integrated with region-of-interest selection, RGB-to-HSI transformation, HSI-based pixel segmentation, 36-bins x 12bits HSI histogramming and sum-of-absolute-difference (SAD) template matching. 32 learned color templates are stored and compared to each image. The chip captures the R, G and B images using in-pixel storage before passing the pixel content to a multiplying digital-to-analog converter (DAC) for white balancing. The DAC can also be used to pipe in images for a PC. The color processing uses a biologically inspired color opponent representation and an analog look-up table to determine the Hue (H) of each pixel. Saturation (S) is computed using a loser-take-all circuit. Intensity (I) is given by the sum color components. A histogram of the segments of the image, constructed by counting the number of pixels falling into 36 Hue intervals of 10 degrees, is stored on chip and compared against the histograms of new segments using SAD comparisons. We demonstrate color-based image segmentation and object recognition with this chip. Running at 30fps, it uses 1mW. To our knowledge, this is the first chip that integrates imaging, color segmentation and color-based object recognition at the focal plane.

Dual-waveband, Focal Plane Arrays (FPAs) based on Hg1-xCdxTe multi-layer structures have previously been produced by the Molecular Beam Epitaxy (MBE) growth technique. It is shown that the multi-layer structures required for dual-waveband devices can also be grown by Metal Organic Vapor Phase Epitaxy (MOVPE). The MOVPE growth process allows excellent control of both the composition and doping profiles and has the advantage of allowing growth on a range of substrates including silicon. Previous research on back-to-back diodes for dual-waveband has concentrated on npn structures. The design of the alternative pnp structures is discussed and a model is developed which gives a good fit to the measured spectra. We report on the design and characterization of dual-waveband detectors including current-voltage and spectral cross talk for the case of two close sub-bands within the 3-5 μm mid-wave infrared (MWIR) spectral range. The mechanisms for spectral cross talk are discussed including incomplete absorption, transistor action and radiative coupling. A custom readout circuit (ROIC) has been designed. This allows the capture of data from the two bands which is spatially aligned but sequential in time.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We present a new technology for uncooled focal plane arrays, which is based on optical readout. An electrooptic crystal, operated in the paraelectric phase, is used as the temperature sensitive element. A lateral readout configuration is utilized, and an entire row of pixels is read simultaneously through electrical triggering. The optical readout diminishes the electronic noise mechanisms resulting in a predicted NETD of 5-7mk. This low NETD of the device is determined by the temperature fluctuations noise, thus approaching the theoretical limit for uncooled FPAs.

An overview of DRS' development of a very unique two-color infrared photodiode architecture for two-color infrared focal-plane arrays based on Hg 1-x Cd x Te is given. One unique feature of this architecture is that it requires only a mono-color based on Hg 1-x Cd x Te material growth technique for its implementation. Some data from this development are presented.

Dynamic Networked Combat Capability is a transformational concept to enable network centric warfare at the tactical level - the immediate attack of targets of opportunity using any and all assets available: any sensor, any effect generator and any decider against any target. More specifically, the DARPA goal is to provide enabling technologies that will permit the Services to build such a capability.

The Defense Advanced Research Projects Agency (DARPA) is developing a new and exciting communications capability through the Optical and Radio Frequency (RF) Combined Link Experiment (ORCLE) program. This program will develop and demonstrate a prototype system that combines free space optical and RF communications into a single networked system to provide compact, robust, high-bandwidth, mobile communications to military forces. ORCLE is a revolutionary approach to communications that will combine the high data rate capability of laser communications, the high reliability of RF communications, and clever network management to ensure high quality, reliable networked communications, even if some of the links are affected by atmospheric or physical obstructions.

The authors describe a procedure they believe to be optimum for determining the path of a ray through an atmosphere described by a radially varying refractive index profile on the Earth. The result is exact for patched quadratic profiles inverse problem and is suitable for calculating ray paths in complex profiles. The method also facilitates greatly the inverse problem.

True 3D displays, whether generated by volume holography, merged stereopsis (requiring glasses), or autostereoscopic methods (stereopsis without the need for special glasses), are useful in a great number of applications, ranging from training through product visualization to computer gaming. Holography provides an excellent 3D image but cannot yet be produced in real time, merged stereopsis results in accommodation-convergence conflict (where distance cues generated by the 3D appearance of the image conflict with those obtained from the angular position of the eyes) and lacks parallax cues, and autostereoscopy produces a 3D image visible only from a small region of space. Physical Optics Corporation is developing the next step in real-time 3D displays, the automultiscopic system, which eliminates accommodation-convergence conflict, produces 3D imagery from any position around the display, and includes true image parallax. Theory of automultiscopic display systems is presented, together with results from our prototype display, which produces 3D video imagery with full parallax cues from any viewing direction.

The U.S. Army, Arizona State University (ASU) and commercial industry have joined forces to create the Flexible Display Center (FDC) at Arizona State University, a large-scale collaborative venture designed to rapidly advance flexible display technology to the brink of commercialization. The Center has completed its startup phase and is now engaged in an intensive and aggressive applied research and development program that will produce high quality, high performance active matrix reflective and emissive flexible display technology demonstrators (TDs). Electrophoretic ink and cholesteric liquid crystals have been selected as Center reflective imaging layer technologies; these technologies are attractive because they are fully reflective and bistable (extremely low power) and because the materials are environmentally robust and intrinsically rugged. Organic light emitting devices (OLEDs) have been chosen as the emissive imaging layer technology. These three electro-optic subsystems will be integrated with a flexible a-Si thin film transistor active matrix backplane platform. We have created the integrated design, backplane fabrication, display assembly, test and evaluation capability to enable rapid cycles of learning and technology development. Backplane fabrication is currently accomplished on a 6” wafer scale pilot line linked to a Manufacturing Execution System and supported by a comprehensive suite of in-fab metrology tools. We are currently installing a GEN II pilot line, with qualified operation slated for 2006. This line will be used to demonstrate process and display form factor capability, while providing high yield low volume manufacturing of pilot-scale levels of technology demonstrators for the Army and our commercial partners.

Current military activity has made great use of small Special Tactics / Special Forces teams operating on the ground in forward areas of battle, directing Battlefield Air Operations (BAO), which include close air support, air traffic control management, and target identification and designation. A recent National Priority has been identified to improve the BAO Kit used by these Special Tactics Groups to reduce errors that may lead to unintended ground casualties. The primary objectives of the upgraded BAO Kit are to 1) improve the range and accuracy of target information; 2) eliminate opportunities for error in weapon delivery; 3) link target coordinate information directly into the weapons computer; and 4) reduce the weight carried by the warfighter by 50%. For these warfighters, L-3 Communications Display Systems and its technology partner, Universal Display Corporation, are utilizing advanced OLED display technology to create a powerful flexible display-based communication device. This will reduce the weight carried by the fighter by combining functions of the present computer, GPS equipment, and radio gear carried into the forward areas of battle. This will give the soldier a larger, higher resolution, increased battery life, and much lighter capability for the viewing of tactical information such as battlefield maps, GIS imaging data, command/control plots, and GPS-assisted navigational maps. Further integration of the device with voice and video messaging options will be explored. Both hand-held roll-up devices and wrist-worn devices are envisioned for the final product.

Significant progress has been made in the development of large area, cost-effective, high performance circuitry on flexible substrates. Several semiconductor and process technologies have been investigated for their potential to achieve the Macroelectronics goals.

A prototype for a Multi-layered Display with variable depth has been successfully constructed. The consiquences with regard to the application space are explored and a preliminary study on the reaction time as a function of depth is explored. Initial results indicate that the reaction time is independent of amount of depth so long as it is greater than zero.

Network Centric Operations (NCO) is placing severe demands on crew members beyond their ability to perform the mission. Links within the Global Information Grid (GIG) provide immense volumes of data from off-platform sensors and information bases that must be transformed into knowledge. This transformation requires extensive processing while displaying information to the operator for rapid assimilation. Demonstrations have shown the operator overload occurs when utilizing the current human-machine interface (HMI) and adding new functions such as those proposed for the new battlespace. In many cases the operator must perform his current duties which severely task the workload while controlling unmanned platforms which may be operating in a different environment than the manned platform operates. The overload precludes increasing situation awareness which is the primary reason for NCO. Managing the flow of data using the current crew station design also reduces heads-up and eye-out operations with an adverse impact on flight safety. A radical change is needed in the design of HMI, making the interfaces more intuitive, to resolve these problems. A target platform has been selected for analysis and demonstration. NCO requirements, both current and projected, for that platform are in analysis. We are evaluating five potential candidates to reduce operator workload in the NCO environment. These are advanced software technologies, large displays, enhanced graphics processing, and voice recognition technology. Combinations of these technologies will be merged in a demonstration which builds upon previous work.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The military display market is analyzed in terms of one of its segments: avionics. Requirements are summarized for 13 technology-driving parameters for direct-view and virtual-view displays in cockpits and cabins. Technical specifications are discussed for selected programs. Avionics stresses available technology and usually requires custom display designs.

Display Aging has been shown to be present in all displays to one degree or another. We will discuss some recent information on Display Aging discussing aging issues in Fluorescent, short arc and Plasma (PLANON) Lamps, LCDs, PDPs, CRTs, and FEDs. This is a very large subject and we will highlight only some of the more important aging issues. In each case, we will briefly describe the display (and or component) and then review some aging aspects of the display (or component). When possible we will compare the aging characteristics in different displays.

In silicon, direct electronic transitions leading to light emission have a low probability of occurrence due to the momentum mismatch between upper and lower electronic levels. Until recently, this had prevented the realization of the long waited silicon optical amplifier and laser. Raman scattering, which describes the interactions of light with vibrational levels, can be used as a way to bypass the indirect band structure of silicon and to obtain amplification and lasing. The Raman approach is very appealing because device can be made in pure silicon with a spectrum that is widely tuneable though the pump laser wavelength. While a new research topic, amplifiers with pulsed gain of 20dB and CW gain of 3 dB have already been demonstrated. Using parametric Raman coupling, wavelength conversion from 1550nm to 1300nm has been achieved. A distinguishing feature of silicon Raman devices, compared to fiber devices, is the electronic modulation capability. By integrating a p-n junction with the silicon gain medium, electrically switched lasers and amplifiers have already been demonstrated. These have many exciting applications. For example, the laser can be directly modulated to transmit data, and can be part of a silicon optoelectronic integrated circuit. At the same time, electrically switched amplifiers represent loss-less optical modulators.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

All optical XOR, AND, and, OR functionality has been demonstrated experimentally using semiconductor optical amplifier (SOA) based devices at 40 Gb/s, 80 Gb/s. The performance of the optical logic operations has been analyzed by solving the rate equation of the SOA numerically. The high-speed operation is limited by the gain and phase recovery times in the SOA. In order to solve these limitations, a differential scheme for XOR operation has been experimentally investigated. This scheme is potentially capable of XOR operation to > 100 Gb/s.

We present high-performance surface-normal modulators based on unique properties of stepped quantum wells (SQWs) around the eye-safe wavelength of 1550 nm. Fabricated devices show nearly two times better efficiency and 7 dB higher extinction ratio compared with the conventional devices with rectangular and coupled-quantum well active layers. Moreover, the optical bandwidth is about 70 nm at a 3dB modulation depth, which is more than five times wider than the optical bandwidth of the conventional devices. Such a wide optical bandwidth eliminates the need for a temperature controller. This is a critical advantage for many applications such as unmanned aerial vehicles (UAVs) and dynamic optical tags (DOTs), where limited volume, power, and weight can be allocated to the modulator system.

We have developed 10, 20, 30, and 40 Gb bandwidth balanced photoreceivers which have applications for both analog and digital fiber optic communications. The devices can operate at C and L optical bands as well as 1064 nm and 1310 nm wavelengths. The analog applications include low noise RF photonic links. The digital applications include 10 Gb and 40 Gb DPSK and DQPSK modulation formats for enhanced sensitivities. The advantages of balanced photoreceivers are: RIN noise cancellation, suppression of even order harmonics, doubling the optical power handling capacity of a photonic link, and better reliability.

Recent progress toward implementing high-density, optical-digital building blocks necessary to accomplish efficient, end-to-end optical interconnect architecture on low cost FR-4 boards has been demonstrated. The optical interconnect system consists of fabricating an optical buffer layer separating board metallurgy from the optical lightwave circuit layer, and implementing optical links between embedded lasers and detectors. We will show an example of 1310 nm light from an edge emitting distributed-feedback or Fabry-Perot laser operating at 10 Gb/s being guided to the photodetector by a polymer waveguide. Both lasers and detector are embedded in the waveguide and all construction is built on a low-cost FR-4 board with 3 levels of metallurgy.

An approach that modifies an analog fiber optic link with a recirculating optical loop as a means to realize a high-speed, high-resolution Analog-to-Digital Converted (ADC) is presented. The loops stores a time-limited microwave signal so that it may be digitized by using a slower, conventional electronic ADC. Detailed analytical analysis of the dynamic range and noise figure shows that under appropriate conditions the microwave signal degradation is sufficiently small so as to allow the digitization of a multi-gigahertz signal with a resolution greater than 10 effective bits. Experimental data is presented which shows that a periodic extension of the input signal can be sustained for well over one hundred periods that in turn suggests an electronic ADC speed-up factor of over 100. The data also shows that polarization effects must be carefully managed to inhibit the loops tendency to lase even though the loop itself contains no frequency-selective elements.

The bandstructure of photonic crystals oers intriguing possibilities for the manipulation of electromagneticwaves. During the last years, research has mainly focussed on the application of these photonic crystal propertiesin the telecom area. We suggest utilization of photonic crystals for sensor applications such as qualitative andquantitative gas and liquid analysis. Taking advantage of the low group velocity and certain mode distributionsfor some k -points in the bandstructure of a photonic crystal should enable the realization of very compact sensordevices. We show dierent device con“gurations of a photonic crystal based on macroporous silicon that ful“llthe demands to serve as a compact gas sensor.Keywords: Photonic Crystals, sensor application, low group velocity, macroporous silicon 1. INTRODUCTION1.1. Photonic Crystals Photonic Crystals (PhCs) are the optical analog to electronic semiconductors, i.e., PhCs are semiconductors forphotons. The concept of PhCs was introduced independently in 1987 by Sajeev John

We survey attempts to accurately diagnose skin cancer in vivo and in real time through the use of optics and automatic computation without the intervention of the clinician. Although no system has yet been shown to have such a capability, commercialization of a variety of diagnostic aids has taken place. We describe our own research into the diagnosis of malignant melanoma, the most lethal form of skin cancer, based on the spectroscopy of diffuse white light reflectance collected with a single multimode fiber after delivery with a multimode fiber bundle. Our clinical study, which collected 82 melanomas and 277 lesions in total, highlights the complexity of this challenging application.

We discuss the fundamental limits of fiber Bragg grating (FBG) wavelength metrology. High-accuracy wavelength measurements are critical for FBG strain sensors because a wavelength measurement uncertainty as small as 1 pm leads to an uncertainty of nearly 1 microstrain. We compare the measurement uncertainties for several common wavelength measurement systems, including tunable laser, optical spectrum analyzer (OSA), and interferometric. We show that when using an OSA it is difficult to achieve a measurement uncertainty better than 10 pm, and if the OSA is not accurately calibrated to a known wavelength reference, then the wavelength measurement uncertainty can be as large as 1 nm. We describe the uncertainties involved in determining peak and/or centroid wavelength from a measured data set. We also discuss calibration references for FBG sensor interrogation units. Wavelength references that are based on molecular absorption lines are often an excellent choice for FBG sensor calibration. However, some interrogation units require a wavelength reference unit based on narrow reflection lines rather than absorption lines. We investigated the application of athermally packaged FBGs as wavelength references, but we found that their wavelengths will drift with time and can undergo large jumps. We concluded that it is difficult to achieve stability better than 4 pm/year in athermally packaged FBGs.

Interactions between acoustic waves and optical modes both propagating along an optical fiber are reviewed for applications in tunable photonic sensory devices. Fiber design parameters in Brillouin scattering sensors, and acoustooptic tunable filters are discussed.

Fibre-optic sensors can show significant advantages against other sensor technologies when installed in the right application. We demonstrated successfully the use of fibre-optic current, temperature and strain sensors in power generators, power combustion turbines, and electric infrastructure and preventive maintenance for transportation systems. All solutions offer enhanced efficiency and availability of the units they were installed in.

The applications of fiber optic sensors on board spacecraft and launchers are discussed based on the experience gained by several ESA funded R&D projects along with the experience of preparing the first spaceflight hardware demonstrations.

An efficient multiplexing method for fiber Bragg grating sensors based on a broadband mode-locked laser source and interferometric interrogation is described. The system has the capability to interrogate several hundred fiber Bragg grating sensors on a single fiber, whilst achieving sub-microstrain resolution over bandwidths greater than 100 kHz. A demonstration system with 8 sensors is presented, which achieves strain resolutions less than 213 n epsilon/Hz(1/2) up to 100 Hz.

A variety of noise measurements have been accomplished on electronic devices incorporating individual single-walled carbon nanotubes. Noise with a 1/f frequency dependence and noise attributed to two-level fluctuators are independently measured, even when these two components occur simultaneously in the same device. We demonstrate the importance of isolating these two components before attempting quantitative analysis, and then proceed to characterize devices as a function of temperature and processing history. High temperature desorption, surface passivation with polymer, and encapsulation in SiO2 films followed by forming gas annealing are three different process pathways which failed to substantially decrease the noise in these devices. In all of the devices measured, the 1/f noise components are found to only weakly decrease with temperature and to be practically independent of processing history. The two-level fluctuators, on the other hand, appear to be thermally activated and their contribution to the total noise typically increases with different processing steps.

We have studied the 1/f noise and the radiation response of transistors with silicon-on-insulator (SOI) buried oxides, and with Al 2 O 3 /SiOxNy/Si(100) gate dielectrics. The former is significant for understanding the response of advanced SOI transistor structures (e.g., double gate devices), and the latter is important for the incorporation of high-K gate dielectrics into advanced MOS processes. The 1/f noise of MOSFETs fabricated on silicon-implanted SOI buried oxides shows little change after 1 Mrad(SiO 2 ) irradiation. Silicon implantation creates shallow electron traps in the buried oxide of the SOI devices, leading to improved radiation tolerance, but also additional noise and bias instabilities. Whether the traps that lead to these instabilities are filled or empty does not significantly affect the 1/f noise of the back-channel transistor. Low frequency noise in the strongly coupled front-to-back (quasi double-gate) mode of device operation is also investigated, and found to help mitigate the 1/f noise in fully depleted SOI MOSFETs. The decrease in noise is associated primarily with an increase in the number of carriers in the channel for this quasi double-gate mode of operation. In transistors with high-K dielectrics, the low-frequency noise is significantly larger than typically observed for high-quality thermal SiO 2 thin films.

The propagation properties of microstructured optical fibers useful for sensing applications are reviewed. The interaction between light and sample can reach 95 % in singlemode hollow core fibers and examples of structures exhibiting such large overlap ratios are described. The generation of 300 nm and 700 nm flat continua of visible and IR light in a single highly nonlinear holey fiber, well suited for the detection of biological species by spectroscopy, is reported. The low temperature sensitivity of long period gratings and of the birefringence in holey fibers is attractive for sensors operating in varying environmental conditions.

We present time-domain electron counting studies on charge fluctuations in a mesoscopic system. In this measurement, a radio-frequency single-electron transistor (RF-SET) acting as a fast electrometer is capacitively coupled to a quantum dot (QD) electrostatically defined in a GaAs/AlGaAs heterostructure. Random telegraph signals (RTSs) were observed on the RF-SET and were interpreted as resulting from individual electrons tunneling into/out of the QD hence switching the QD charge state between N and N+1 electrons near the charge degeneracy point. Periodic behavior of the switching events is observed as the number of average electrons in the electron box is decreased one by one. The occupation time of the excess electron is directly measured and changes from a few microseconds to a few milliseconds as the tunneling resistance of the QD is increased. Histogram of the occupation time obtained from the time-domain electron counting measurements agrees well with the frequency-domain power spectrum analysis, both suggesting a Poissonian process at the charge degenerate point, in agreement with a model consisting of two charge states. Real time electron counting techniques can play a powerful role in studies on temporal electronic correlations, as well as quantum information processing schemes. Techniques that will improve the charge sensitivity of the RF-SET will also be discussed.

POF has found wide use in multimode intensity-based sensor applications. The characteristics of POF, limit the link (sensor)length to a few tens of meters and the sensor operational temperature cannot exceed 80°C. However, when these limitations are not important, POF sensors can offer their most significant advantage over corresponding glass fibre sensors, and this is a significantly lower system cost. Following recent new developments in POF technology, such as fibre gratings and microstructured POF, one looks forward to new and more exciting POF sensor applications. The future of POF sensors is concluded as optimistic.

We apply a method to filter relevant information from the correlation coefficient matrix by extracting a network of relevant interactions. This method succeeds to generate networks with the same hierarchical structure of the Minimum Spanning Tree but containing a larger amount of links resulting in a richer network topology allowing loops and cliques. In Tumminello et al., 1 we have shown that this method, applied to a financial portfolio of 100 stocks in the USA equity markets, is pretty efficient in filtering relevant information about the clustering of the system and its hierarchical structure both on the whole system and within each cluster. In particular, we have found that triangular loops and 4 element cliques have important and significant relations with the market structure and properties. Here we apply this filtering procedure to the analysis of correlation in two different kind of interest rate time series (16 Eurodollars and 34 US interest rates).

Pulsed Laser Chemical Vapor Deposition (PLCVD) has been used to fabricate single atoms doped nanoparticles of magnesium sulfide. These particles were dispersed in optically transparent Poly-methyl-methacrylate (PMMA) films for near field nano-microscopy such that each nanoparticle doped with a single europium atom falls in the focusing range of the near field microscope. By atomic tailoring, the concentration of the doubly ionized europium, Eu2+, has been maximized in these nanoparticles. The energy and the oscillator strength of the 4f7-4f65d1 electronic transition has been tailored to maximize its addressing by photons in single atom spectroscopy experiments. Results have been presented on the fabrication of these single atom doped nanoparticles and their spectroscopy by laser excited fluorescence technique. Studies of a single Eu2+ ion by confocal micro-spectroscopy are in progress.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have been developing "fiber optic nerve systems" for "smart structures and smart materials", in which an optical fiber acts as sensor to measure distribution of strain along it. The original technology, "Brillouin Optical Correlation Domain Analysis: BOCDA" has been proposed and developed to analyze the distributed strain along the fiber by use of synthesis of correlation characteristics of continuous lightwave. Adopting this technology, "fiber optic nerve systems" with quite a high spatial resolution and measurement speed, have been established.

Light emitting diodes (LEDs) are excellent candidates for the applications requiring low noise light sources with wavelengths ranging from 200 nm to 900 nm. These applications include the detection of fluorescence from protein molecules excited with the ultraviolet (UV) light (200-300nm) for identifying miniscule amounts of hazardous biological pathogens. The detection system including the light source must exhibit low noise and high stability over tens of minutes. In comparison with xenon, tungsten halogen lamps, lasers, and other conventional UV sources, UV LEDs are more stable, have lower noise, are smaller, cheaper, and easier to use. We report on the low frequency fluctuations of the current and light intensity of LEDs (fabricated by SET, Inc.) with wavelengths ranging from 265nm to 340nm. The results are compared with the noise properties of the halogen lamps and other commercially available LEDs with the wavelengths of 375nm, 505nm and 740nm. We show that the LEDs fabricated by Sensor Electronic technology, Inc. are suitable for studying steady state and time-varying UV fluorescence of biological materials. The correlation coefficient between the current and light intensity fluctuations varies with the LED current and load resistance. This dependence is explained in terms of the contributions to the 1/f noise from the active region and from the LED series resistance. The noise level could be reduced by operating the LEDs at a certain optimum current level and by using a large external series resistance (in the current source driving mode).

A detailed understanding of noise characteristics is essential for the design of a high signal-to-noise ratio (SNR) reader sensor. We intend to correlate the microstructure to the source of magnetic noises for improving the magnetic stability of the recording heads. A dynamic magnetic sensitivity mapping (MSM) system is designed to image the magnetic noise sources in sub-micrometer sized recording heads. A nanometer sized magnetic force microscopy (MFM) tip was used to apply a well-defined, localized magnetic field on the air bearing surface (ABS) of the head. For a certain area position of the free layer with incoherent rotation of the magnetic moment, this localized magnetic field will cause magnetic instability in the head, and this instability will show up as electrical noise on the output signal. Because most of the noise related to magnetic domain fluctuation is dominated at the low frequency region, our study concentrates on the spatial characterization of the noise source in a frequency range of 20 kHz to 60 kHz. Recording the average amplitude of the noise spectrum due to the excitation in the measured frequency range as a function of the tip's position, the location of the magnetic noise source can be identified. Magnetic noise images have been obtained by our system for some recording giant magnetoresistance (GMR) and tunnel magnetoresistance (TMR) recording heads. Noise MSM images of some unstable recording heads clearly show the spatially uneven noise.

Inhomogeneous broadening in optically addressed solids provides a convenient technique for individually addressing a large number of optically active defects in a crystal. Such a capability is important for quantum computer development. However, the random nature of inhomogeneous broadening can limit scalability. Here, techniques that can be used to suppress inhomogeneous broadening will be reviewed including a recently proposed VLSI quantum computer design based on nitrogen-vacancy (NV) color centers in diamond.

We report systematic investigations on hot-electron degradation in GaN-based HEMTs with different gate recess depths, d r , fabricated by reactive ion etching. The experimental data stipulate two different mechanisms underlying the hot-electron degradations of the devices. During the initial phase of hot-electron injection significant changes were observed in the dc characteristics of the devices and the flicker noise power spectral density, SV(f). The degradations were partially recovered by annealing the devices at 100°C for 20 minutes. It is shown that for stress time ts≤25 hours the reverse bias gate current, IG , decreases systematically with ts, whereas SV(f) fluctuates randomly. Detailed analyses of SV(f) measured over a wide range temperatures show that the initial degradations originate from the percolation of carriers in the 2DEG. The significant increase in the flicker noise during the initial phase of high-voltage stress is due to the generation of H+ at the AlGaN/GaN interface. The fluctuations in the magnitudes of SV(f) for ts≤25 hours originate from the motion of the H+ in the direction of the electric field. This results in the modulation of the percolation path leading to significant variations in SV(f) as a function of ts. For ts>25 hours both IG and SV(f) are stabilized resulting from the drifting of the H+ away from the gate region. Further stressing beyond 25 hours indicate strong dependencies of the device lifetimes on dr suggesting significant material degradation due to the reactive ion etching process for the fabrication of the gate recesses. Detailed characterization of the noise show that the final irreversible degradation is due to the generation of traps at the AlGaN/GaN interface.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We report our direct observation of the Barkhausen avalanche in ferromagnetic thin film systems, where a collective spin behavior produces nontrivial fluctuations in magnetization change under an external magnetic field. For this study, we develop and use two direct full-field magnetic imaging techniques: magneto-optical microscope magnetometer (MOMM) and magnetic transmission X-ray microscopy (MTXM). From a direct visualization and a statistical analysis of the fluctuating domain images for Co thin films, we investigate the scaling behavior of the Barkhausen avalanche both on spatial and temporal scales using MOMM. We also investigate the reproducibility of the Barkhausen avalanche process. Interestingly, the partially stochastic nucleation behavior is observed for CoCrPt alloy films by means of MTXM on a nanometer scale comparable to the fundamental length scales such as the Barkhausen volume and the grain size of the polycrystalline films. Via these direct full-field observation techniques, dynamic details of Barkhausen avalanche are revealed.

New techniques for introducing micro- and nanostructures in the core region of optical waveguides or fibers offer new opportunities to influence the propagation and coupling conditions of guided light. Such modifications include e.g. single mode conditions for optical fibers, the range of the numerical aperture, dispersion properties, mode shape, extended wavelength ranges or guiding with multiple cores. Although many developments were triggered by possible applications in communication technology, these new opportunities in functionality offer attractive chances also for new investigations into sensing with optical fibers.

We will describe keyed communication in quantum noise (KCQ) and how it can be used for either data encryption or key generation. Specifically, we will focus on the AlphaEta protocol for data encryption where the role of quantum noise will be discussed. Additionally, the potential of using classical noise to enhance security via deliberate signal randomization (DSR) will be investigated. We will also investigate the effect of unwanted impairments, such as nonlinearities in a wavelength-division-multiplexed fiber transmission system, and how they affect the ultimate allowable propagation distance. Our simulations and experiments suggest that AlphaEta-protocol based physical-layer encryption is compatible with long-haul optical transmission systems operating at Gb/s data rates.

We address anomalous transport phenomena in arrays of semiconductor nanocrystals (quantum dots): Transient power-law decay of current as a response to a step in large bias voltage applied across the array, as well as memory effects observed after successive applications of the bias voltage. A novel phenomenological model of transport in such systems is proposed, capable of rationalizing both anomalous transport and memory. The model describes electron transport by a stationary Levy process of transmission events and therefore requires no time dependence of system properties. The long tail in the waiting time distribution gives rise to a nonstationary response in the presence of a voltage pulse. Noise measurements agree well with the predicted non-Poissonian fluctuations in current. We briefly discuss possible microscopic mechanisms that could cause the anomalous statistics in transmission.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.