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There has been considerable interest in the use of the Submillimeter/THz (SMM/THz) spectral region for gas analysis and detection. This has been driven both by the importance of the application and the THz-TDS community. In this paper we will discuss and compare the attributes of an attractive alternative: cw submillimeter spectroscopy. Particular attention will be paid to sensitivity, specificity, and the investigations of harsh environments. A particularly simple system approach, the FAst Scan Submillimeter Spectroscopy Technique (FASSST), will be discussed and a compact and potentially very low cost implementation described. Results will be presented which include the analyses of complex mixtures of gases with absolute specificity.

A biological(bio)-molecular inspired electronic architecture is presented that offers the potential for defining nanoscale sensor platforms with enhanced capabilities for sensing terahertz (THz) frequency bio-signatures. This architecture makes strategic use of integrated biological elements to enable communication and high-level function within densely-packed nanoelectronic systems. In particular, this architecture introduces a new paradigm for establishing hybrid Electro-THz-Optical (ETO) communication channels where the THz-frequency spectral characteristics that are uniquely associated with the embedded bio-molecules are utilized directly. Since the functionality of this architecture is built upon the spectral characteristics of bio-molecules, this immediately allows for defining new methods for enhanced sensing of THz bio-signatures. First, this integrated sensor concept greatly facilitates the collection of THz bio-signatures associated with embedded bio-molecules via interactions with the time-dependent signals propagating through the nanoelectronic circuit. Second, it leads to a new Multi-State Spectral Sensing (MS3) approach where bio-signature information can be collected from multiple metastable state conformations. This paper will also introduce a new class of prototype devices that utilize THz-sensitive bio-molecules to achieve molecular-level sensing and functionality. Here, new simulation results are presented for a class of bio-molecular components that exhibit the prescribed type of ETO characteristics required for realizing integrated sensor platforms. Most noteworthy, this research derives THz spectral bio-signatures for organic molecules that are amenable to photo-induced metastable-state conformations and establishes an initial scientific foundation and design blueprint for an enhanced THz bio-signature sensing capability.

There is a need for ever more effective security screening to detect an increasing variety of threats. Many techniques employing different parts of the electromagnetic spectrum from radio up to X- and gamma-ray are in use. Terahertz radiation, which lies between microwave and infrared, is the last part to be exploited for want, until the last few years, of suitable sources and detectors. Terahertz imaging and spectroscopy has been shown to have the potential to use very low levels of this non-ionising radiation to detect and identify objects hidden under clothing. This paper describes recent work on the development of prototype systems using terahertz to provide new capabilities in people screening - both at security checkpoints and stand-off detection for remote detection of explosives and both metallic and non-metallic weapons.

New high-sensitivity solid-state magnetoresistive (MR) sensor technologies offer significant advantages in nondestructive evaluation (NDE) systems. A key advantage of MR sensors is a flat frequency response extending from dc to hundreds of MHz, making them particularly attractive for low-frequency and multi-frequency eddy current detection for deep-flaw detection and depth profiling. MR sensors are mass produced by thin film processing techniques similar to integrated circuit manufacturing, dramatically reducing the cost per sensor. The fabrication process is compatible with silicon circuit technology, allowing integration of sensors with on-chip signal processing. MR sensors can easily be produced in dense arrays for rapid, single-pass scanning of large areas. The small size and low power consumption of these solid-state magnetic sensors enable the assembly of compact arrays of sensors on a variety of substrates as well as on-chip sensor arrays. Arrays have been fabricated with sensor spacing as small as 5 μm. This paper presents a review of the state of the art in MR sensors and applications in NDE. The physical principles, manufacturing process, and performance characteristics of the three main types of MR devices, anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR) and tunneling magnetoresistance (TMR) are discussed. Their performance is compared to other magnetic sensor technologies for NDE applications. Finally, we provide a comprehensive review of the literature on NDE applications of MR sensors.

Luminescent coatings applications have been increased dramatically over the last decade as imaging capacities have advanced. These coatings have been used to monitor surface temperature and air pressure (oxygen sensing) in testing facilities around the world. Through the commercial suppliers of these coatings, custom assembled hardware systems and especially data reduction and analysis software, the use of smart luminescent coatings are starting to find their way in to inspection monitoring and nondestructive evaluation testing. The use of a temperature sensitive paint for example, can be a potential replacement for infrared imaging where IR techniques are limited due to access, reflections and complex geometries. Detection of the luminescent signal can use simple intensity ratio methods with synchronized pulsing systems to capture frequency responses in imaging applications. Time or frequency methods allow signals to be detected in the presence of high background noise that allow measurements that were previously unobtainable. This paper describes general luminescent sensors, detection methods and examples of coatings that are applied over test examples or embedded in materials to measure or monitor the health of a specimen.

With the strong increase of mask complexity and associated price for each new technology node, mask less lithography represents more and more an interesting and complementary alternative for ASIC manufacturing especially in the fields of low volume and leading eadge technology applications. In the semiconductor business where prices and cycle time are constantly pressured, the capability and flexibility of the electron beam direct write offer an effective real cost and cycle time opportunity thanks to its high-resolution capability but also to its ability to print, modify or correct design everywhere in a circuit. This paper highlights application examples where the advantages of this lithography solution are demonstrated for advanced research and development application with the patterning of 45 nm SRAM and for the fast validation of architecture designs. This work confirms that mask less lithography can be transparently placed into production environment, in association with the "golden" optical lithography reference.

Semiconductor process development teams are faced with increasing process and integration complexity while the time between lithographic capability and volume production has remained more or less constant over the last decade. Lithography tools have often gated the volume checkpoint of a new device node on the ITRS roadmap. The processes have to be redeveloped after the tooling capability for the new groundrule is obtained since straight scaling is no longer sufficient. In certain cases the time window that the process development teams have is actually decreasing. In the extreme, some forecasts are showing that by the time the 45nm technology node is scheduled for volume production, the tooling vendors will just begin shipping the tools required for this technology node. To address this time pressure, IBM has implemented a hybrid-lithography strategy that marries the advantages of optical lithography (high throughput) with electron beam direct write lithography (high resolution and alignment capability). This hybrid-lithography scheme allows for the timely development of semiconductor processes for the 32nm node, and beyond. In this paper we will describe how hybrid lithography has enabled early process integration and device learning and how IBM applied e-beam & optical hybrid lithography to create the world's smallest working SRAM cell.

This paper first gives an overview of state-of-the-art simulation of semiconductor laser devices. The relevant physical models for multi dimensional, electro thermal, and optical simulation as well as an advanced active region model are reviewed. The second part of this work deals with the management of laser simulation projects and the extraction of the relevant data from simulation results. A new tool called PCM Explorer is presented that is suitable for the integration of numerical models in the design and manufacturing process of semiconductor lasers. Both the device performance as well as the process yield can be predicted with the combination of a comprehensive device simulator, some measurement data for calibration purposes, and the statistical process evaluation tool.

We have demonstrated high power, linearly polarized output from an all-fiber laser using an integrated polarizing fiber. In this paper, we will detail the design, fabrication and operation of the single polarization fiber as well as the fiber laser experiments.

In this invited paper, we will discuss the use of quantum dots as nonlinear optical elements in fiber laser sources. Furthemore, a review of the fabrication of the first low-loss (< 0.5 dB/cm) ion-exchanged waveguides in a quantum-dot-doped glass will be presented. We will discuss the coupling, propagation, absorption, and scattering losses in these waveguides. The near-field mode profile along with the refractive index profile of these waveguides will be presented. This PbS quantum-dot-doped glass was chosen due to its attractive optical gain and bleaching characteristics at wavelengths throughout the near infrared. This bleaching of the ground-state optical transition has been utilized for passive modelocking of a variety of lasers in the near infrared. In addition, we will discuss some of the potential integrated and fiber optics applications of our quantum-dot-doped waveguides.

This review paper is based on the 2004 UCLA Seminar on Imaging and Informatics (http://www.radnet.ucla.edu/Arrowhead2004/) which is a joint endeavour between the UCLA and the CARS organization, focussing on workflow analysis tools and the digital operating room. Eleven specific presentations of the Arrowhead Seminar have been summarized in this review referring to redesigning perioperative care for a high velocity OR, intraoperative ultrasound process and model, surgical workflow and surgical PACS, an integrated view , interactions in the surgical OR, workflow automation strategies and target applications, visualisation solutions for the operating room, navigating the fifth dimension, and design of digital operating rooms and interventional suites

Heat shock proteins (HSP) are critical components of a complex defense mechanism essential for preserving cell survival under adverse environmental conditions. It is inevitable that hyperthermia will enhance tumor tissue viability, due to HSP expression in regions where temperatures are insufficient to coagulate proteins, and would likely increase the probability of cancer recurrence. Although hyperthermia therapy is commonly used in conjunction with radiotherapy, chemotherapy, and gene therapy to increase therapeutic effectiveness, the efficacy of these therapies can be substantially hindered due to HSP expression when hyperthermia is applied prior to these procedures. Therefore, in planning hyperthermia protocols, prediction of the HSP response of the tumor must be incorporated into the treatment plan to optimize the thermal dose delivery and permit prediction of overall tissue response. In this paper, we present a highly accurate, adaptive, finite element tumor model capable of predicting the HSP expression distribution and tissue damage region based on measured cellular data when hyperthermia protocols are specified. Cubic spline representations of HSP27 and HSP70, and Arrhenius damage models were integrated into the finite element model to enable prediction of the HSP expression and damage distribution in the tissue following laser heating. Application of the model can enable optimized treatment planning by controlling of the tissue response to therapy based on accurate prediction of the HSP expression and cell damage distribution.

Piezoelectric semiconductor with heterostructure can be treated as a piezoelectric transducer for the generation of acoustic waves with wavelength less than 10 nm (nano-acoustic waves) by optical technique. This optical piezoelectric transducer has also been utilized for the detection of the nano-acoustic waves (NAW). In this paper, we discuss the generation, detection, and propagation of nano-acoustic waves in piezoelectric semiconductors. We demonstrate that the acoustic frequency of the NAW can be tuned by an optical control technique. Besides, we have also developed an acoustic sensor with THz bandwidth which can be used to study NAW propagation control devices such as nano-phononic bandgap crystal. We demonstrated that the roughness of an interface can be evaluated by the NAW with a resolution less than 1 nm through the acoustic phasefront distortion effect. With the optical piezoelectric transducer, nano-ultrasonics, which is analogous to typical ultrasonics but on the nanometer scale, has been successfully developed.

This paper reports on progress in the VUV spectroscopy of surfaces and nanostructures, as facilitated by twoexperimental innovations. In Scanning Probe Energy Loss Spectroscopy (SPELS) electrons backscattered from the tip-surface junction are detected when an STM tip is operated in field emission mode. Energy loss features in the range 1-300 eV have been observed, corresponding to optical absorption spectra from the IR through to the VUV and X-rayregions. Recent data suggests in addition that SPELS can record local secondary electron emission spectra. SPELSoffers spatial resolution on the 10 nm scale. High Harmonic Generation (HHG) of VUV light provides a complementaryprobe of the excited states of surfaces and nanostructures, offering a temporal resolution of order 100 fs or below. Theutility of the High Harmonic source is demonstrated by an investigation of the visible fluorescence from thin films ofpassivated CdSe nanocrystals, as a function of excitation energy, decay time and temperature, which thus emerge as newscintillators for VUV applications.Keywords : Scanning tunnelling microscopy; Electron energy loss spectroscopy (EELS); High harmonic generation;femtosecond; CdSe; Quantum dots.

Laser-based technologies have played an important role in manufacturing of hard disk drives. The applications include disk texturing, precision bending of the suspension, precision adjust of the shape of the slider carrying the magnetic read/write head and protection against electrostatic discharge (ESD) in the read/write heads. Disk texturing allows one to reduce slider/disk stiction during contact by producing bumps only a few nanometers high and a few microns in diameter at the landing zone of the disk. Laser bending of the suspension allows one to precisely control gram load, the pre-load force with which the slider is pushed towards the disk, as well as the pitch and roll static attitudes of the slider, which strongly influence its flying characteristics. Laser crown adjust helps control slider flatness to within a few nanometers, with high precision and predictability. These technologies allow one to reduce both the mean and the tolerance of slider/disk spacing, thus effectively enabling higher magnetic recording densities. Laser technology helps to protect the sensitive magnetic read head against electrostatic discharge by allowing one to put an electrical short on the head during most of the part's handling, then removing it using a sharply focussed laser beam during final stages of drive assembly. Laser technology, with its ability to process small areas with precision positioning, being contact free and hence largely contamination free and being able reach areas with optical fibers not easily accessible by mechanical means is ideally suited for these manufacturing processes. In this paper we review the physical mechanisms underlying these technologies and possible future applications of lasers in disk drive manufacturing.

Laser micromaching systems are being used in mainstream high-volume semiconductor applications. Two of those processes, via drilling and thin wafer dicing, are discussed in this paper. Via drilling has been proven viable for forming through chip and blind vias. The inherent flexibility of the laser process makes it possible to control via depth, diameter and sidewall slope. As a mask-less process, laser via drilling can be cost affective and highly flexible in its application. Thin wafer dicing reduces the breakage and damage to thin silicon wafers. A new process has been developed that improves the die strength of laser singulated devices beyond that obtained using conventional sawing techniques.

The laser-induced plasma-assisted ablation (LIPAA) process developed by our group, in which a single conventional pulsed laser is only used, makes it possible to perform high-quality and high-speed glass microfabrication. Up to the present, this process has been widely applied for micromachining of various transparent hard and soft materials. In this process, a laser beam is first directed to a glass substrate placed in vacuum or air. The laser beam passes through the substrate since the wavelength of the laser beam must have no absorption by the substrate for the LIPAA process. The transmitted laser beam is absorbed by a solid target (typically a metal), located behind the substrate. The target is then ablated, resulting in plasma generation. Due to the interaction of the laser beam and the laser-induced plasma, significant ablation takes place at the rear surface of the substrate. Recently, we have developed the proto-type LIPAA system using a second harmonic of diode pumped Q-switched Nd:YAG laser for the practical use. In this paper, we will demonstrate micromachining, crack-free marking, color marking and dicing of glass materials. Additionally, selective metallization of glass and polyimide by the LIPAA process followed by metal chemical-plating is investigated. The discussion includes mechanism and practical applications in micro-electronics industry of the LIPAA process.

Short-pulse lasers of femtosecond and picosecond durations are used in ultrahigh precision processing of optical, electronic, and micro-mechanical devices. In this paper we discuss the fabrication of high quality photonic crystal band-pass filters with femtosecond laser pulses. We also discuss the parallel processing of inkjet nozzles with a picosecond laser. A laser milling algorithm and a high accuracy beam scanner allows the formation of precisely shaped holes as inkjet nozzles, and an efficient diffractive beam splitter allows the simultaneous drilling of many hundreds of holes for low cost manufacturing.

Paper and parchment cleaning with lasers provides the advantage to be a contact-less and dry process. The absence of chemical agents, its spectroscopic selectivity, micro-precision, computer-aided handling, and the combination with on-line diagnostic techniques makes it attractive for restoration applications. This technique, however, is not only limited by the evaporation of such delicate protein or cellulose fibre structures (i.e. the ablation threshold) or by discolorations, which can be easily detected by the naked eye or by microscopic inspection. Even when the aesthetic appearance is not altered, invisible irreversible chemical modifications may affect the long-term aging behavior negatively. In such cases, only diagnostic tools sensitive for chemical changes can probe the limits of laser cleaning. Deviations of chemical conversion threshold fluences from the well-established ablation threshold fluence values were investigated by multi-spectral imaging techniques at parchment or paper model systems and historical originals. Ultraviolet, visible and infrared reflection, but also visible fluorescence were employed using an imaging system, which operates in a spectral range from 320 nm to 1550 nm. Visible imaging allowed an accurate documentation of the color appearance of the artwork before and after the laser treatment. In-depth information of chemical modifications could be gained by the infrared imaging mode. Surface chemical identification was performed by both diffuse-reflection imaging in the ultraviolet range between 320 and 400 nm, and by visible fluorescence imaging using a 365 nm light source. The results for excimer laser treatment at 308 nm show that not only the laser fluence but also the age of the artefact strongly affects the chemical conversion threshold. Most substrates older than at least several decades exhibited much higher chemical stability than new model systems. This is a strong indication that the aging status of both parchment and paper artefact plays a major role in assessing the laser cleaning limits. That means that the laser processing behavior of model systems can be compared with that of original fibrous artworks to only a very limited extent, and that original artefacts have to be treated rather as individual specimens.

Electro-Active Paper (EAPap) is a paper that produces large displacement with small force under electrical excitation. EAPap is made with a chemically treated paper by bonding thin aluminum foils on both sides of the paper to comprise electrodes. When electric voltage is applied on the electrodes the EAPap produces bending displacement. However, the displacement output has been unstable and degraded with time scale. To improve the bending performance of EAPap, different paper fibers-broad-leaf, needle-leaf, bacteria cellulose and Korean traditional paper, and additive chemicals are tested. It was observed that needle-leaf paper exhibits better results then others. By eliminating the effect of adhesive layer and selecting a proper paper fiber, the displacement output has been stable with long time scale. The operational principle of EAPap is, we believe, based on the electrostriction effect associated with intermolecular interaction of the constituents of the paper. To confirm this result, more investigation of the paper quality should be followed in the beginning of paper manufacturing process. Since EAPaps are quite simple to fabricate and lightweight, various applications including flexible speakers, active sound absorbing materials and smart shape control devices can be possible.

A procedure of inspection of femtosecond laser induced mass transfer processes has been suggested that is based on pump-probe Doppler tomography. In the experiments we used mode-locked Ti:sapphire laser with output power up to 150 mW.. In our experiments focused laser radiation induced on the surface of the target mass transfer processes (melting and convection). The Doppler shifted backscattered radiation was registered by heterodyne scheme based on Michelson interferometer. We have obtained information about depth and distribution of convection flows within melted paraffin bath with high spatial resolution (Dz~15mm). We propose optical heterodyning technique based on OCT for obtaining temporal distribution of backscattered photons from media irradiated by Cr:forsterite femtosecond laser. The temporal resolution is about 60 fs. The technique was used for sheet paper porosity diagnostics.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Papermaking process consists in a succession of unit operations that are successively the forming section, the press section and finally the drying section. Forming and pressing are on the scope of this paper as they may influence the aspect of the studied material: paper. The main objective is to characterize paper and more specifically its visual quality, mainly due to marking which consists in successive white and dark strips. A proposed method is described in order to analyze the quality of this visual aspect of paper, which is a very important factor for the consumer. This paper is therefore devoted to the presentation of an industrial tool to Digital Image Processing that allows the evaluation of cigarette paper marking quality. This problem is delicate as different technical and physical parameters have some influence on the paper appearance. For example the whiteness or the opacity of paper influences the evaluation of the quality of the marking. Furthermore, an expert of paper cigarette who observes the paper lying on a black support carries out the classical test of quality evaluation. Thus the reflection of light is mainly observed instead of the look- through aspect. Usually, this determination is made by the experienced eye of the expert who may distinguish between 5 to 6 classes of paper quality. Moreover, sensibility and subjectivity play an important role in this grading establishment. The aim of the presented tool is to obtain an object classification of the paper marking quality. Image analysis is used in order to mimic the expert experience. In a first step, the image acquisition is done using a standard scanner. Then developed software analyzes the obtained image numerically. The sensibility of the image analysis is high, and the results are repeatable. The classification of different cigarette papers using this method provided the same results as the human expert, pointing out the validity of the developed method. Some experimental results are presented in order to illustrate the industrial interest for this method. We present in a first part the new method to obtain an evaluation of the quality of a material property (paper aspect) from image analysis. Then example of measurements obtained on different paper samples, using a classical scanner, illustrate the proposed methodology. Finally, some comparison between the classifications obtained from the proposed method and the human expertise are presented to underline the interest of the proposed objective method.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Papermaking process consists in a succession of unit operations having for main objective the expression of water out of the wet paper pad. The three main stages are successively, the forming section, the press section and finally the drying section. Furthermore, another operation (calendering) may be used to improve the surface smoothness. Forming, pressing and drying are not on the scope of this paper, but the influence of formation and calendering on surface roughness is analyzed. The main objective is to characterize the materials and specially its superficial structure. The proposed model is described in order to analyze this topographical aspect. Some experimental results are presented in order to illustrate the interest of this method to better understand physical properties. This work is therefore dedicated to the description of the proposed model: the studied surface is measured at a microscopic scale using for example, a classical stylus profilometry method. Then the obtained surface is transformed using a conformal mapping that retains the surface orientations. Due to the anisotropy of the fiber distribution in the plane of the sheet, the resulting surface is often not isotropic. Hence, the micro facets that identify the interfaces between pores and solid (fibers in the studied case) at the micro level are transformed into a macroscopic equivalent structure. Furthermore, an ellipsoid may be fit to the experimental data in order to obtain a simple model. The ellipticities are proved to be linked for paper to both fiber orientation (through other optical methods) and roughness. These parameters (ellipticities) are shown to be very significant for different end-use properties. Indeed, they shown to be correlated to printing or optical properties, such as gloss for example. We present in a first part the method to obtain a macroscopic description from physical microscopic measurements. Then measurements carried on different paper samples, using a classical profilometry methods, illustrate the proposed methodology. Some comparisons with conventional roughness indexes are presented. Finally, some applications, and more precisely end use properties, are shown to underline the interest of the proposed method. These geometrical characteristics may be deduced from experimental results whatever the microscopic size is.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Standards for creating and integrating information about patients, equipment, and procedures are vitally needed when planning for an efficient Operating Room (OR). The DICOM Working Group 24 (WG24) has been established to develop DICOM objects and services related to Image Guided Surgery (IGS). To determine these standards, it is important to define day-to-day, step-by-step surgical workflow practices and create surgery workflow models per procedures or per variable cases. A well-defined workflow and a high fidelity patient model will be the base of activities for both, radiation therapy and surgery. Considering the present and future requirements for surgical planning and intervention, such a patient model must be n-dimensional, were n may include the spatial and temporal dimensions as well as a number of functional variables. As the boundaries between radiation therapy, surgery and interventional radiology are becoming less well-defined, precise patient models will become the greatest common denominator for all therapeutic disciplines. In addition to imaging, the focus of WG24 should, therefore, also be to serve the therapeutic disciplines by enabling modelling technology to be based on standards.

An IETM is intended to be the functional equivalent of a paper-based Technical Manual (TM), and in most cases a total replacement for paper manual. In this paper, we will describe some of document image understanding technologies applied to the conversion of paper-based TMs to IETMs. Using these advanced technologies allow us to convert paper-based TMs to class 1/2 IETMs. However, these were not sufficient for an automated integrated logistics support system in the ROC Department of Defense. An advanced IETM system is therefore required. Such class 4/5 like IETM system could provide intelligent display of information and other user applications such as diagnostics, intelligent design and manufacturing, or computer-managed training. The author has developed some of the advanced functions, and examples will be shown to demonstrate the new aspect of IETMs.

Fluorescence from paper following excitation by either ultraviolet or visible light gives information on the chemical composition of the paper. This can be used for on-line monitoring of the paper during production. Such measurements can be performed non-intrusively at sampling rates high enough to give a sub-millimetre resolution at paper webs moving at velocities higher than 20 metres per second. Two types of fluorescence meters, operating at different wavelengths, have been constructed. Together with an optical speedometer they have been tested at newsprint producing paper mills. A fluorescence based method for scanning cross-directional newsprint profiles in the laboratory has been developed. From these measurements the relative shrinkage of the paper during drying can be calculated using time-frequency analysis.

The paper formation is one of the most important properties of the paper but remains a difficult property to determine. A method for determining this property has been developed. This method based on light transmission image analysis uses the power spectra of the Fourier transform to analyze the floc distribution. The method has been tested for various furnishes and allows a well discrimination between different qualities of formation that does the standard formation number.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Stiffness properties of paper materials can readily be characterized in the laboratory using conventional ultrasonic techniques. For on-line inspection on a paper machine, due to the high translation velocity and the somewhat fragile nature of the moving paper web, contact ultrasonic techniques using piezoelectric transducers are of limited use. To overcome this limitation, non-contact laser- based ultrasonic techniques can be used. Due to the rough surface of the paper, the reflected light is composed of many speckles. For efficient detection, the receiver must be able to process as many speckles as possible. Adaptive receivers using the photorefractive or photo-emf effects are characterized by a large etendue, and thus, are well suited for detection on paper and paperboard. Moreover, the translation velocity of the moving web implies that the detection system must adapt extremely quickly to the changing speckle pattern. In this work, a photo-emf receiver was used to detect Lamb waves excited using a pulsed Nd:YAG laser in moving paper. Experiments were performed using a variable-speed web simulator at speeds much higher than 1 m.s -1 . Results corresponding to various translation speeds are shown, demonstrating the feasibility of laser- based ultrasound for on-machine inspection of paper and paperboard during production.

Laser-Based Ultrasound (LBU) systems are now entering their maturity years by penetrating the factory in both the areas of non-destructive testing and process control. A LBU system can be used for the on-line characterization of a paper web in a paper mill. Compared to contact techniques, LBU is able to generate and detect on a paper web both symmetric and antisymmetric waves with a non-contact tool which is the spot of the generation laser. This provides all at once a rich amount of data about the stiffness properties of the sheet. To demonstrate this concept we made some experiments on static paper first, our ultimate goal being to monitor the stiffness properties of a paper web, on-line, at industrial speeds. A photorefractive interferometer using the two-wave mixing method with a continuous electric field applied to a BSO crystal has been built for ultrasound detection. Results are presented on different paper grades, using a Nd:YAG laser for generation. Both A0 (anti- symmetric) and S0 (symmetric) modes of Lamb waves have been detected with acceptable signal to noise ratio in single laser shot. The dispersive nature of A0 wave is clearly visible as well as the higher frequency content of S0 wave.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have developed a functional distributed fiber-optic stress sensor by synthesis of the optical coherence function (SOCF). The technique determines the location of stress-induced polarization mode coupling in a polarizationmaintaining fiber (PMF) by measuring the optical path difference (OPD) between the fast mode and the slow mode in PMF with SOCF. By modulating the frequency of the lightwave from a super-structure-grating distributed Bragg reflector laser diode (SSG-DBR-LD) in a stepwise waveform, the coherence function is synthesized into a series of periodical peaks in the meaning of time-integration. The period is controlled to allow only one coherence peak enter the range of the PM fiber under test. Then we can measure the polarization mode coupling at the position corresponding to the peak. The position of the peak is adjusted by using a phase modulation proportional to the frequency modulation. Therefore, polarization mode coupling distribution along the fiber can be obtained. Up to date, one end of the sensing fiber is used as the input end, and the other as the output end. This scheme is generally not convenient for remote applications. In this presentation, we report two new effective methods that unify the input and the output to one end of the fiber. In one scheme, a mirror plus a polarizer is attached to the far end of the PM fiber. The other scheme employs a polarization beam splitter (PBS) attached to the far end of the PM fiber. The light beam output from the PBS in one polarization direction is fed back into the fiber through the PBS in the perpendicular polarization direction. Experimental demonstrations for both schemes are presented.

We report on an experimental comparison between PMN-PT single crystal resonators with commercially available QCM resonators showing significant superiority for new sensors over conventional quartz. Thickness acoustic mode resonators made out of PMN-PT film were fabricated for these tests. The thickness mode resonators make use of a mechanically polished PMN-PT single crystal film of thickness 30μm. The sensor response to methanol vapor condensation shows a frequency shift for the PMN-PT resonator 1000 times larger under the same environmental conditions than the commercial quartz microbalance sensor. A surface acoustic mode resonator using mechanically polished PMN-PT single crystal film of thickness 100μm was also fabricated and tested. The dimensions of the PZN-PT film sample were 5×2×0.12mm 3 . Thin gold interdigitated electrodes were applied on one side of the sample. A 50nm-thick gold film was evaporated on the surface and patterned using standard photolithography. This resonator sample also exhibits a resonance frequency similar to that of a commercial quartz microbalance sensor. A large frequency drop or sensitivity is again found for the PMN-PT sensors than the quartz sensors in this case. The frequency shift in the PMN-PT surface mode resonator is ~300 times larger to methanol vapor loading than in the quartz resonator.

An optomechatronic system based on one-dimensional ultrasound detector array for intravascular pressure measurement is presented. The proposed structure is based on optical linear ring resonators array. The applied pressure on ring resonator will change the physical parameters such as effective cross section of the ring and finally the effective index of refraction. The transmitted intensity changes and the measured output power could be used for measuring the pressure. Also, for rejection of common errors after photodetectors blocks, differential amplifiers can be utilized. For incident light coupling to the rings, the integrated 3-dB couplers are used. The effect of pressure on single ring is simulated and the effects of coupling coefficient, coupler loss and ring resonator diameter are investigated. This structure easily can be extended to two-dimensional cases. So, the proposed structure can be used for intravascular imaging including low noise and high integration and precision.

Numerous equally-spaced emission lines can be generated by stimulated Raman scattering and subsequent four-wave Raman mixing. The spectral domain extends from the near-infrared to the deep-ultraviolet, and then an ultimately-short optical pulse can be generated by phase locking in the process of four-wave Raman mixing. In fact, an intense 17-fs optical pulse has been generated using this technique. A comb of 1.6-fs optical pulses, i.e., the shortest optical pulses, has also been generated by other researchers. On the other hand, it is possible to generate highly-repetitive pulses using a continuous wave (CW) laser as a pump source and molecular hydrogen as a Raman medium in a high-finesse cavity. Coherent superposition of the two-color beam comprising of the fundamental beam and the Stokes beam provides a sinusoidal wave modulated at 17 THz. It is also possible to generate more than three emission lines simultaneously, which should generate an impulsive wave. It is noted that such Raman emission can be generated in a hollow-core fiber, making the device extremely simple. Such a device may have a potential for use in basic science and technology, e.g., the generation of a three-primary-color laser for display.

The physical principles underlying a three-dimensional (3D) laser microstructuring technique are outlined, its applications for the fabrication of 3D (nano)micro-structured materials are presented. The direct laser writing and holographic recording in SU-8 photoresist are described. The limits of the lateral and axial light localization of a Gaussian pulse/beam at the focus are derived for the multi-photon absorption taking into account the threshold of photomodification. Prospective holographic patterns formed by interference of circularly and linearly polarized beams are discussed.

Negative dielectric planar waveguides is reviewed toward silicon nanophotonics from the point of view of two-dimensional optical waves. Excitation, index-guiding, squeeze of optical beam width, adiabatic mode conversion of two-dimensional optical waves are discussed theoretically. The efficient excitation method of surface plasmon polariton is proposed as an adiabatic coupler from optical fibers. This is a gateway from conventional dielectric waveguides to nanophotonics. Low-dimensional optical waves at exotic interfaces are studied for the interface including non-metallic negative dielectrics, negative permeability materials and left-handed materials. Future perspectives toward polaritonics is discussed.

We propose a strategy for a micromanipulation method using surface stabilized ferroelectric liquid crystals (SSFLC). By adjusting the frequency of the applied ac electric field, the surface layers that cannot follow an applied ac electric field are constructed in SSFLC. In addition, by applying a sawtooth wave voltage, net flow along the smectic layer is generated. The flow direction is reversed by changing the polarity of the sawtooth wave. Consequently, the particles dispersed in SSFLC can be driven bidirectionally along the smectic layer. The particle velocity depends on the temperature, amplitude and frequency of the applied voltage.

Nitride-semiconductor technologies for blue lasers are reviewed. Nitride semiconductors from GaN to InN are covered with respect to MOVPE growth and characteristics. For GaN, two-step growth significantly improves crystalline characteristics, such as the concentration of residual carriers, mobility, and surface morphology. For InGaN, a key material for the emitting layer of blue lasers, the use of nitrogen as the carrier and bubbling gases for metalorganic sources enhances indium incorporation, and composition control has been achieved. The phase separation of InGaAlN system has been semiempirically predicted using the strictly regular solution model. As substrates for the epitaxial growth, a several materials are discussed along with the affect of the substrate polarity on the characteristics of epitaxially grown GaN. P- and n-type doping are also briefly examined. Looking at future prospects for blue lasers, the effect of polarization in device structures and the bulk-crystal growth for substrates are described.

The human visual system has an amazing sensitivity-even a single photon catch can trigger the release of a signal in a rod photoreceptor cell under certain circumstances. However, behaviorally it requires on an average 5-8 photons for a human to "see" a flash of light. This discrepancy is due to the intrinsic "dark noise" in the visual system. Various aspects of human visual sensitivity to single photons are reviewed and discussed.

Photons are continuously absorbed and emitted by all living cells. A possible means of releasing energy when an electron changes energy states during a biochemical reaction is via biophoton emission. An example of energy transfer in biological systems is the process of photosynthesis. Biophoton emission has also been proposed as one possible mechanism responsible for intra- and intercellular communication (information transfer) as well as for regulation of biological and biochemical functions within cells and living systems. Measurements by other researchers of this emission have shown it has the properties of coherent light and is measurable from the UV through the near IR. Experimental evidence gathered by various researchers since the 1920's indicates that light plays an important role in certain biological functions and processes. Through a series of experiments we have observed resonance effects between plant parts measured using a highly sensitive, low noise, cooled CCD in total darkness in a light-tight chamber. Dynamical systems theory offers a plausible explanation for resonance effects we have observed. The role of photonic interaction at the systemic level in biological systems has received relatively little attention. Yet, a better understanding of these processes would help us in deciphering the nature and role of light in biological systems.

Photonic crystal devices are now being produced for a variety of functions-and the need to provide thermal control of the behaviour suggests the use of thermo-optic effects. It has emerged that thermo-optic effects can provide useful modulation, switching and tuning capability. Future trends indicate fast, low-power, thermo-optically operated photonic crystal and photonic wire devices-and the possibility of simultaneous athermal characteristics.

Limiting factors for short-wavelength QCL designs are discussed, and a model is described to predict the short-wavelength limit for strain-balanced QCL structures. High performance is predicted at wavelengths as short as 3.0mm based on a conduction band offset of 0.9 eV in the GaInAs/AlInAs materials. Recent work is presented on the growth of strained materials using gas-source molecular beam epitaxy to investigate the model predictions. Advanced material characterization, including HR-STEM, high-resolution x-ray diffraction, photoluminescence, atomic force microscopy, and wafer-scale uniformity and repeatability are demonstrated for strain-balanced QCL structures. Laser testing results are presented for QCLs operating at ~4.8mm, and lastly, predictions for further performance improvement at short wavelengths are discussed.

Recent advances in electro-optic transmitters for improved transmission performances are presented, with special focus on lithium niobate based devices for extended reach applications.

Microspheres possess high quality factor morphology-dependent resonances, i.e., whispering gallery modes. These resonances have narrow linewidths necessary for applications to compact optoelectronic devices for wavelength division multiplexing. The morphology dependent resonances have high quality factors of 104 and 105 with channel spacings of 0.14 nm in glass and 0.05 nm in silicon microspheres.

We report on the recent progresses of our work on the design, fabrication and integration of micro/nano-scale photonic devices and optical waveguide arrays for optical printed circuit boards (O-PCBs) and VLSI photonic applications. The waveguides are designed and fabricated by thermal embossing and ultraviolet (UV) radiated embossing of polymer materials. The photonic devices include vertically coupled surface emitting laser (VCSEL) microlasers, microlenses, 45-degree reflection couplers, directional couplers, arrayed waveguide grating structures, multimode interference (MMI) devices and photodetectors in micro/nano-scale. These de-vices are optically interconnected and integrated for O-PCB assembly and VLSI micro/nano-photonics. De-tailed procedures of fabricating and implementing these devices and assembly of O-PCB are described. The O-PCBs are to perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards or substrates. We report on the result of the optical transmission performances of these as-sembled O-PCBs up to 2.5 Gbps and 10 Gbps. For the design, fabrication, and VLSI integration of nano-scale photonic devices, we used photonic crystal structures. Characteristics of these devices are also described.

We report a true left-handed (LH) behavior in a composite metamaterial consisting of periodically arranged split ring resonator (SRR) and wire structures. The magnetic resonance of the SRR structure is demonstrated by comparing the transmission spectra of SRRs with that of closed SRRs. We confirmed experimentally that the effective plasma frequency of the LH material composed of SRRs and wires is lower than the plasma frequency of the wires. A well-defined left-handed transmission band with a peak value of -1.2 dB (–0.3 dB/cm) is obtained. We also report the transmission characteristics of a 2D composite metamaterial (CMM) structure in free space. At the frequencies where left-handed transmission takes place, we experimentally confirmed that the CMM structure has effective negative refractive index. Phase shift between consecutive numbers of layers of CMM is measured and phase velocity is shown to be negative at the relevant frequency range. Refractive index values obtained from the refraction experiments and the phase measurements are in good agreement. The experimental results agree extremely well with the theoretical calculations. Keywords: Negative refraction, negative phase velocity, split ring resonator, left-handed medium, metamaterial Veselago predicted that a medium with negative permittivity, , and negative permeability, µ , will exhibit negative indices of refraction [1]. When both the permittivity and the permeability are negative the electric field, the magnetic field and the wavevector components form a left-handed coordinate system, hence the name left-handed material (LHM) is used for description. Such a medium is expected to exhibit unusual physical properties such as negative refraction, reversal of Doppler shift, backward Cherenkov radiation. A medium with < 0 can easily be realized, e.g. by periodically arranged metallic wires [2]. On the other hand, the µ ( ) < 0 was a challenge due to lack of magnetic charge . Pendry et. al suggested that a periodic array of metallic split ring resonator (SRR) structures exhibit µ ( ) < 0 close to magnetic resonance frequency p [3]. This proposal brought the possibility of observing left-handed medium in to reality. Recently, this idea is brought to experimental investigation by constructing a composite metamaterial (CMM) consisting of two components which have ( ) < 0, a periodically arranged wire medium, and µ ( ) < 0, a periodically arranged SRR medium, simultaneously over a certain frequency range, respectively [4,5]. Various studies employing different structure designs extended this investigation [4-8]. Negative refraction of electromagnetic waves at the interface of CMMs is also observed [9-11] which supported the existence of a LHM. The parameters and µ can be obtained by a retrieval procedure from the numerically calculated transmission and reflection data for finite size CMMs [12,13], under the assumption of a homogeneous medium. This procedure confirmed [14] that a medium composed of SRRs and wires can indeed be characterized by effective and µ . A medium transmits electromagnetic waves when both and µ have the same sign, i.e., both are negative or both are positive. If they have opposite signs the medium effectively reflects the incoming electromagnetic wave. The existence of a pass band for the CMM within the respective stop bands of SRR-only and wire-only mediums is intuitively considered as evidence for LH behavior. We experimentally demonstrate that the dielectric response of the CMM differs substantially from that of the wire-only medium, by measuring

We report on optical analogues of well-known electronic phenomena such as Bloch oscillations and electrical Zener breakdown. We describe and detail the experimental observation of Bloch oscillations and resonant Zener tunneling of light waves in static and time-resolved transmission measurements performed on optical superlattices. Optical superlattices are formed by one-dimensional photonic structures (coupled microcavities) of high optical quality and are specifically designed to represent a tilted photonic crystal band. In the tilted bands condition the miniband of degenerate cavity modes turns into an optical Wannier-Stark ladder (WSL). This allows an ultrashort light pulse to bounce between the tilted photonic band edges and hence to perform Bloch oscillations, the period of which is defined by the frequency separation of the WSL states. When the superlattice is designed such that two minibands are formed within the stop band, at a critical value of the tilt of photonic bands the two WSLs couple within the superlattice structure. This results in a formation of a resonant tunneling channel in the minigap region, where the light transmission boosts from 0.3% to over 43%. The latter case describes the resonant Zener tunneling of light waves.

We analyze the impact of slow intraband relaxation and strong carrier localization on the characteristics of quantum dot (QD) lasers. Relatively long intraband relaxation times and population filling of the QD ground state lead to carrier pile-up on excited states, reducing the laser efficiency and maximum output power. Strong carrier localization in the QDs and consequently large thermal hopping time within the QD ensemble results in the absence of quasi-thermal equilibrium under lasing conditions, as evidenced by stimulated and spontaneous emission spectra. The impact of these specific physical characteristics of QD active regions on the laser high-frequency modulation properties is analyzed, particularly with regards to the differential gain, the gain compression and the linewidth enhancement factors.

When the emission of light by molecules, excitons etc. takes place close to a thin metallic film, coupling of power to surface plasmon-polariton (SPP) modes supported by the metal film often dominates. We explore the nature of the SPP modes and examine how the energy lost to them can be recovered through the use of periodic, wavelength scale microstructure. We show that the photoluminescence emission from a structure containing is much stronger than that from a similar planar structure. We look at the importance of the exact details of the microstructure on the emission process.

A low temperature MEMS process integrated with an infrared detector technology has been developed. The integrated microsystem is capable of electrically selecting narrow wavelength bands in the range from 1.6 to 2.5 μm within the short-wavelength infrared (SWIR) region of the electromagnetic spectrum. The integrated fabrication process is compatible with two-dimensional infrared focal plane array technology. The demonstration prototypes consist of both HgCdTe SWIR photoconductive as well as high density vertically integrated photodiode (HDVIP®) detectors, two distributed Bragg mirrors formed of Ge-SiO-Ge, an air-gap optical cavity, and a silicon nitride membrane for structural support. The tuning spectrum from fabricated MEMS filters on photoconductive detectors indicates a wide tuning range and high percentage transmission. Tuning is achieved with a voltage of only 7.5 V, and the FWHM ranged from 95-105 nm over a tuning range of 2.2 μm to 1.85 μm. The same MEMS filters, though unreleased, and with the sacrificial layer within the optical cavity, have been fabricated on planarised SWIR HDVIP® photodiodes with FWHM of less than 60 nm centred at a wavelength of approximately 1.8 μm. Finite element modelling of various geometries for the silicon nitride membrane will also be presented. The modelling is used to optimize the filter geometry in terms of fill factor, mirror displacement versus applied voltage, and membrane bowing.

NASA's planetary exploration strategy is primarily targeted to the detection of extant or extinct signs of life. Thus, the agency is moving towards more in-situ landed missions as evidenced by the recent, successful demonstration of twin Mars Exploration Rovers. Also, future robotic exploration platforms are expected to evolve towards sophisticated analytical laboratories composed of multi-instrument suites. MEMS technology is very attractive for in-situ planetary exploration because of the promise of a diverse and capable set of advanced, low mass and low-power devices and instruments. At JPL, we are exploiting this diversity of MEMS for the development of a new class of miniaturized instruments for planetary exploration. In particular, two examples of this approach are the development of an Electron Luminescence X-ray Spectrometer (ELXS), and a Force-Detected Nuclear Magnetic Resonance (FDNMR) Spectrometer. The ELXS is a compact (< 1 kg) electron-beam based microinstrument that can determine the chemical composition of samples in air via electron-excited x-ray fluorescence and cathodoluminescence. The enabling technology is a 200-nm-thick, MEMS-fabricated silicon nitride membrane that encapsulates the evacuated electron column while yet being thin enough to allow electron transmission into the ambient atmosphere. The MEMS FDNMR spectrometer, at 2-mm diameter, will be the smallest NMR spectrometer in the world. The significant innovation in this technology is the ability to immerse the sample in a homogenous, uniform magnetic field required for high-resolution NMR spectroscopy. The NMR signal is detected using the principle of modulated dipole-dipole interaction between the sample's nuclear magnetic moment and a 60-micron-diameter detector magnet. Finally, the future development path for both of these technologies, culminating ultimately in infusion into space missions, is discussed.