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In this work, a high-performance stripe-shaped light-emitting diode (LED) with a size of $7500\times 300\,\,\mu \text{m}^{{2}}$ is reported. With the optimized electrode design, the current can be evenly injected into the elongated chip, achieving a uniform light distribution without the use of external optics. Compared with the conventional cubic LED, the light output performance of the stripe-shaped LED (S-LED) at high current levels is significantly improved, which is mainly due to the enhanced heat dissipation. White light emission is also demonstrated by covering the chip with the yellow phosphor film. With the advantages of reduced luminous exitance, uniform illumination, and improved light output, the S-LEDs are not only suitable for various lighting applications but can also be used as backlight units for display panels. [ABSTRACT FROM AUTHOR]

In this paper, two novel multidimensional striping noise compensation (SNC) algorithms for push-broom hyperspectral cameras (PBHCs) have been developed. The SNC algorithms employ a novel pixelwise, affine image-degradation model, which assumes that the striping noise (SN) parameters are spatially uncorrelated, spectrally independent, and decoupled from the camera’s spectral response. Algorithms simultaneously exploit the spatial and temporal information contained in an image as well as the spectral information contained at adjacent spectral images. The multidimensional SNC algorithms were successfully tested on real hyperspectral data from both a commercial PBHC operating in the spectral range of 400–1000 nm, at a resolution of 1.04 nm, and the ESA earth-observing CHRIS/PROBA sensor. [ABSTRACT FROM PUBLISHER]

A novel integration method for the production of cost-effective optoelectronic printed circuit boards (OE PCBs) is presented. The proposed integration method allows fabrication of OE PCBs with manufacturing processes common to the electronics industry while enabling direct attachment of electronic components onto the board with solder reflow processes as well as board assembly with automated pick-and-place tools. The OE PCB design is based on the use of polymer multimode waveguides, end-fired optical coupling schemes, and simple electro-optic connectors, eliminating the need for additional optical components in the optical layer, such as micro-mirrors and micro-lenses. A proof-of-concept low-cost optical transceiver produced with the proposed integration method is presented. This transceiver is fabricated on a low-cost FR4 substrate, comprises a polymer Y-splitter together with the electronic circuitry of the transmitter and receiver modules and achieves error-free 10-Gb/s bidirectional data transmission. Theoretical studies on the optical coupling efficiencies and alignment tolerances achieved with the employed end-fired coupling schemes are presented while experimental results on the optical transmission characteristics, frequency response, and data transmission performance of the integrated optical links are reported. The demonstrated optoelectronic unit can be used as a front-end optical network unit in short-reach datacommunication links. [ABSTRACT FROM AUTHOR]

Over the last decade, portable, active optical sensors (AOS) have become tools in production agriculture both for mapping crops and soils and also for applying agrochemicals. These sensors are often referred to as “proximal” active optical sensors, in recognition of their deployment at sensor-target distances in the order of meters. Unfortunately most users have little understanding of the underlying physics (optics) or construction of these sensors. This paper sets out to document the fundamental electro-optical principles by which these devices operate and to document the mathematical rules governing the use of data produced by these devices. In particular, emphasis is placed on the inverse-square law of optics and how it affects AOS measurements. The basis for utilizing sensor measurements in more complex mathematical functions is also presented, including manipulation of the individual wavelength response data to derive information regarding the distance variation between the sensor and the target. [ABSTRACT FROM PUBLISHER]

This paper describes Si photonics and the key application to fiber-to-the-home (FTTH). Mass production in terms of complementary metal-oxide-semiconductor technology is a prerequisite for Si photonics to provide a cost-effective solution, and FTTH should meet this requirement. We describe a design of the FTTH chip architecture with wavelength-division. multiplexing based on ring-resonator demultiplexers and multiplexers. The grand challenge of Si photonics for this application is the production of Ge photodetectors and modulators. [ABSTRACT FROM AUTHOR]

We describe a computational imaging technique to extend the depth-of-field of a 94-GHz imaging system. The technique uses a cubic phase element in the pupil plane of the system to render system operation relatively insensitive to object distance. However, the cubic phase element also introduces aberrations but, since these are fixed and known, we remove them using post-detection signal processing. We present experimental results that validate system performance and indicate a greater than four-fold increase in depth-of-field from 17′ to greater than 68′. [ABSTRACT FROM AUTHOR]

When ultrafast laser pulses are tightly focused inside a transparent medium, various nonlinear optical phenomena readily occur at the focal point. These phenomena at the focal point can be utilized for nonlinear-optical microscopy, nanosurgery inside biological samples, device fabrication inside transparent materials, and welding of transparent materials. We review these new techniques from a unified viewpoint. [ABSTRACT FROM AUTHOR]

The novelty of this paper is indicated by a series of experimental measurements aimed at enhancing the detectability of targets immersed in scattered solutions. The experimental results clearly show that polarimetric images of superior quality can be obtained by doping the background surrounding the target with polar or high-dielectric molecules, yielding an enhanced contrast and specificity of the target. In addition, it is observed that degree of linear polarization (DOLP) images exhibit superior image characteristics with respect to total intensity (S0) images with the increase in the concentration of the optical scattering agents. [ABSTRACT FROM AUTHOR]

In this paper, we show that patterned metallic surfaces can support localized resonant modes if a suitable defect in the periodicity of the structure is introduced. For those modes, optical losses due to radiative leakage perpendicular to the metallic plane can be significantly reduced by properly tuning the geometry of the defect-mode surface cavity. A design strategy based on the investigation of the electromagnetic field in the reciprocal space is suggested. [ABSTRACT FROM AUTHOR]

Sparse signal representations and approximations from overcomplete dictionaries have become an invaluable tool recently. In this paper, we develop a new, heuristic, graph-structured, sparse signal representation algorithm for overcomplete dictionaries that can be decomposed into subdictionaries and whose dictionary elements can be arranged in a hierarchy. Around this algorithm, we construct a methodology for advanced image formation in wide-angle synthetic aperture radar (SAR), defining an approach for joint anisotropy characterization and image formation. Additionally, we develop a coordinate descent method for jointly optimizing a parameterized dictionary and recovering a sparse representation using that dictionary. The motivation is to characterize a phenomenon in wide-angle SAR that has not been given much attention before: migratory scattering centers, i.e., scatterers whose apparent spatial location depends on aspect angle. Finally, we address the topic of recovering solutions that are sparse in more than one objective domain by introducing a suitable sparsifying cost function. We encode geometric objectives into SAR image formation through sparsity in two domains, including the normal parameter space of the Hough transform. [ABSTRACT FROM AUTHOR]

A numerical model for multiwavelength actively mode-locked erbium-doped fiber lasers (AML-EDFL) is presented. Using the model, the influences of four-wave mixing (FWM) and phase modulation effects (i.e., self-phase modulation (SPM) and cross-phase modulation (XPM)) can be studied, respectively. We use it to investigate AML-EDFLs incorporating a highly nonlinear fiber (HNLF) and explore the mechanisms for gain competition suppression (GCS). The net dispersion of the cavity is found critical for GCS. In the small dispersion regime, FWM dominates GCS, but SPM and XPM deteriorate the output pulses. In the large anomalous dispersion regime, SPM and XPM, however, enhance GCS and produce high-quality pulses. Degree of GCS is also quantitatively evaluated. The simulation results are at last confirmed by experiments. [ABSTRACT FROM AUTHOR]

Using a wedged and antireflection-coated diamond heatspreader, a continuously tunable semiconductor disk laser with intracavity second-harmonic generation (SHG) is demonstrated. Output powers of > 600 mW tunable over 10 nm around 530 nm are obtained. Finite-element modeling shows that the use of a diamond heatspreader for thermal management—in contrast to substrate thinning approaches—permits power scaling across the 670-2300-nm range of these lasers. Using a green laser as an exemplar, this paper details the issues involved in translating this spectral coverage to the ultraviolet and visible via SHG. Polarization and wavelength selection are discussed and the adopted approaches presented. Almost 1 W of second-harmonic light at 530 nm is demonstrated, with an efficiency of 11% with respect to the incident pump power. [ABSTRACT FROM AUTHOR]

Multimodality imaging is becoming increasingly important in medical imaging. Since the motivation for combining multiple imaging modalities is generally to improve diagnostic or prognostic accuracy, the benefits of multimodality imaging cannot be assessed through the display of example images. Instead, we must use objective, task-based measures of image quality to draw valid conclusions about system performance. In this paper, we will present a general framework for utilizing objective, task-based measures of image quality in assessing multimodality and adaptive imaging systems. We introduce a classification scheme for multimodality and adaptive imaging systems and provide a mathematical description of the imaging chain along with block diagrams to provide a visual illustration. We show that the task-based methodology developed for evaluating single-modality imaging can be applied, with minor modifications, to multimodality and adaptive imaging. We discuss strategies for practical implementing of task-based methods to assess and optimize multimodality imaging systems. A Task-Based Approach to Adaptive and Multimodality Imaging. [ABSTRACT FROM AUTHOR]

Modern X-ray imaging systems require low noise high-count-rate multichannel front-end electronics. Such systems widely use charge-sensitive amplifiers (CSA) with pole-zero cancellation (PZC) circuits for sensor readout. CSAs in multi-channel ASICs often include continuous reset systems based on MOS transistors discharging the integrating capacitance. Noise requirements for such front-end electronics put the effective CSA feedback resistance in the range of hundreds of MΩ. On the other hand, the high input pulse rate generates a dc voltage shift at the CSA output that modifies the CSA feedback resistance and degrades the PZC circuit performance. In the paper we analyze these problems and propose a novel circuit solution to bias transistors in the CSA feedback and in the PZC circuit. This bias circuit tracks the above mentioned voltage shift at the CSA output and ensures proper cancellation of the CSA feedback pole even in the case of high rates of input pulses. We present measurements of a test structure for the continuous CSA feedback discharge and implementation of this circuit in a fast multichannel ASIC manufactured in the 0.35 μm CMOS technology. The circuit performance for the high input pulse rate is described in detail. [ABSTRACT FROM AUTHOR]

We have demonstrated a 2-D droplet manipulation platform allowing fully optical manipulation of droplets on a photosensitive surface. Optically controlled injection, transport, separation, and multiple droplet manipulation have been achieved for nanoliter-size droplets. These functions are realized by sandwiching the droplets between two optoelectrowetting (OEW) surfaces. Optical illumination on OEW surfaces changes the surface wettability locally through the electrowetting mechanism. Optical illumination turns the initially Teflon-coated surface from hydrophobic to hydrophilic. This process is reversible and can be controlled in real time. We have achieved a maximum transport speed of 78 mm/s for a 100-nL droplet using a scanning laser beam. We have also demonstrated a fully decoupled 2-D multidroplet manipulation on the OEW surfaces. Potentially, the OEW mechanism can be scaled up to process a large number of liquid droplets using projected optical images for high throughput applications. [ABSTRACT FROM AUTHOR]

This paper presents an integrated color imaging system for taking images in extremely high dynamic range scenes. The system first fuses several differently exposed raw images to acquire more intensity information. The effective dynamic range of the image raw data can be extended to 256 times ~five differently exposed images are fused. Then it runs edge detection iterations to extract the image details in different luminance levels. The proposed tone reproduction algorithm equalizes the histogram of the extracted fine edges which tends to assign larger dynamic range for highly populated regions. Finally, the local contrast enhancement is performed to further refine the image details. The experimental results show that the proposed high dynamic range imaging system has good performance on both tone and color reproduction'. [ABSTRACT FROM AUTHOR]

The photomechanicai properties of carbon nanotubes (CNTs) enable the construction of CNT-based optical actuators. Employing a microelectromechanical systems-compatible nanotube-patterning process by plasma etching, CNT ensembles are integrated into microsystems to realize microoptomechanical systems (MOMS) (CNT-MOMS), where nanotubes behave as both the structural materials and the actuation mechanism. In this paper, following the CNT-MOMS principle, we report on all-optical micromirrors from the CNTs. Photomechanical actuation of single-wall CNTs from polymer-/nanotube-film bimorph structures is designed to actuate the micromirrors. A large mirror angular displacement of 19° is obtained under laser illumination. Bidirectional rotation of the micromirrors is realized by the incorporation of two symmetrical serpentine bimorph actuators with the mirror surface. Furthermore, to add controllability to the micromirror rotations, absorptive-type optical filters are combined with the mirror structure in a "suspended" filter assembly. With green and red optical filters incorporated in the micromirrors, they show rotational selectivities of 10 : 1 and 20 : 1 for the 532- and 658-nm lasers, respectively. Depending on the wavelength of the incoming light, it could be selectively modulated into opposite directions by the micromirror. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar (SAR) autofocus techniques that optimize sharpness metrics can produce excellent restorations in comparison with conventional autofocus approaches. To help formalize the understanding of metric-based SAR autofocus methods, and to gain more insight into their performance, we present a theoretical analysis of these techniques using simple image models. Specifically, we consider the intensity-squared metric, and a dominant point-targets image model, and derive expressions for the resulting objective function. We examine the conditions under which the perfectly focused image models correspond to stationary points of the objective function. A key contribution is that we demonstrate formally, for the specific case of intensity-squared minimization autofocus, the mechanism by which metric-based methods utilize the multichannel defocusing model of SAR autofocus to enforce the stationary point property for multiple image columns. Furthermore, our analysis shows that the objective function has a special separble property through which it can be well approximated locally by a sum of 1-D functions of each phase error component. This allows fast performance through solving a sequence of 1-D optimization problems for each phase component simultaneously. Simulation results using the proposed models and actual SAR imagery confirm that the analysis extends well to realistic situations. [ABSTRACT FROM AUTHOR]

We investigated the degradation behavior of distributed feedback lasers by employing the optical-beam-induced current measurement technique. We showed that the degradation mechanism is governed by diffused defects at the waveguide other than those in the vicinity of the antireflection facet. In addition, we found that a diffused source is probably generated in the upper InP cladding layer above the grating during the growth of the upper InP cladding layer. [ABSTRACT FROM AUTHOR]

Conventional image copy detection research concentrates on finding features that are robust enough to resist various kinds of image attacks. However, finding a globally effective feature is difficult and, in many cases, domain dependent. Instead of simply extracting features from copyrighted images directly, we propose a new framework called the extended feature set for detecting copies of images. In our approach, virtual prior attacks are applied to copyrighted images to generate novel features, which serve as training data. The copy-detection problem can be solved by learning classifiers from the training data, thus, generated. Our approach can be integrated into existing copy detectors to further improve their performance. Experiment results demonstrate that the proposed approach can substantially enhance the accuracy of copy detection. [ABSTRACT FROM AUTHOR]

Automatic ultrasound (US) image segmentation is a difficult task due to the quantity of noise present in the images and the lack of information in several zones produced by the acquisition conditions. In this paper, we propose a method that combines shape priors and image information to achieve this task. In particular, we introduce knowledge about the rib-eye shape using a set of images manually segmented by experts. A method is proposed for the automatic segmentation of new samples in which a closed curve is fitted taking into account both the US image information and the geodesic distance between the evolving curve and the estimated mean rib-eye shape in a shape space. This method can be used to solve similar problems that arise when dealing with US images in other fields. The method was successfully tested over a data-base composed of 610 US images, for which we have the manual segmentations of two experts. [ABSTRACT FROM AUTHOR]

We report on the frequency stabilization of extended-cavity diode lasers against rotovibrational absorption lines of water vapor at around 0.94 μm, by means of the frequency modulation spectroscopy technique. A minimum frequency instability of ∼30 kHz has been obtained for integration times in the range from 1 to 100 s. [ABSTRACT FROM AUTHOR]

In this paper, we report our systematic study of a promising absolute-calibration technique of analog photodetectors based on the properties of parametric down conversion. Our formal results and a preliminary uncertainty analysis show that the proposed method can be effectively developed with interesting applications to metrology. [ABSTRACT FROM AUTHOR]

Demosaicing is a process of obtaining a full-color image by interpolating the missing colors of an image captured from a single sensor color filter array. This paper provides an effective and low-complexity iterative demosaicing algorithm applying a weighted-edge interpolation to handle green pixels followed by a series of color-difference interpolation to update red, blue, and green pixels. Based on our experiments of images, we enable the algorithm a well-designed stopping condition and predetermine the proper weights of interpolation. Experimental results show that the proposed method performs much better than three state-of-the-art demosaicing techniques in terms of both computational cost and image quality. In comparison to the algorithm of successive approximation, the algorithm proposed here reduces mean squared error up to 14.5% while requiring computational cost only 22% on average. That is, it takes less time but performs better. [ABSTRACT FROM AUTHOR]

This paper presents an image capture and storage module (ICSM) system for capturing image data displayed on a TV and storing the captured image in a memory card without degrading the image quality based on an existing multimedia playback system (MMPS). The ICSM system consists of a capture bridge and storage bridge module. First, the capture bridge module, designed using FPGA, captures the image data displayed on the TV, then transforms the captured image data into a signal acceptable to the processor. Thereafter, the storage bridge module, including a multimedia processor, stores the image data received from the capture bridge module in a memory card after JPEG compression. The efficiency of the ICSM system based on application to an actual TV system with a 1280×720 resolution is verified through hardware implementation.. [ABSTRACT FROM AUTHOR]

A two modes rate equation model for vertical-cavity surface-emitting lasers (VCSELs) subject to optical feedback from an extremely short external cavity (ESEC) is presented. By making use of it we develop a map of bistability to investigate the parametric dependence of polarization properties of VCSELs in such configuration, finding out a periodic dependence of the polarization switching (PS) currents on the ESEC length. By increasing the external mirror reflectivity we can make this periodic dependence stronger and strongly asymmetric providing the possibility to prevent PS for any injection current achieving polarization stabilization in VCSELs. Further numerical simulations with isotropic and non isotropic feedback show how parameters as the compression coefficients, the frequency splitting between the linearly polarized (LP) modes, the differential gain and the top mirror reflection coefficient, affect the map of bistability. [ABSTRACT FROM AUTHOR]

Pendry in his paper, "Negative refraction makes a perfect lens" (Phys. Rev. Left., vol. 85, no. 18, pp. 3966-3969,2000) put forward an idea for a lens made of a lossless metamaterial slab with n = -1, that may provide focusing with resolution beyond the conventional limit. In his analysis, the evanescent wave inside such a lossless double-negative (DNG) slab is "growing:' and thus it "compensate" the decaying exponential outside of it, providing the subwavelength lensing properties of this system. Here, we examine this debated issue of "growing exponential" from an equivalent circuit viewpoint by analyzing a set of distributed-circuit elements representing evanescent wave interaction with a lossless slab of ONG medium. Our analysis shows that, under certain conditions, the current in series elements and the voltage at the element nodes may attain the dominant increasing due to the suitable resonance of the loss less circuit, providing an alternative physical explanation for "growing exponential" in Pendry's lens and similar subwavelength imaging systems. [ABSTRACT FROM AUTHOR]

This paper addresses two challenging issues in unsupervised multiscale texture segmentation: determining adequate spatial and feature resolutions for different regions of the image, and utilizing information across different scales/resolutions. The center of a homogeneous texture is analyzed using coarse spatial resolution, and its border is detected using fine spatial resolution so as to locate the boundary accurately. The extraction of texture features is achieved via a multiresolution pyramid. The feature values are integrated across scales/resolutions adaptively. The number of textures is determined automatically using the variance ratio criterion. Experimental results on synthetic and real images demonstrate the improvement in performance of the proposed multiscale scheme over single scale approaches. [ABSTRACT FROM AUTHOR]

A new analysis leading to an exact and efficient algorithm is presented for calculating directly and without numerical differentiation the mode dispersion characteristics of cylindrical dielectric waveguides of arbitrary refractive-index profile. The new algorithm is based on the equivalent transmission-line (T-L) technique. From Maxwell's equations, we derive an equivalent T-L circuit for a cylindrical dielectric waveguide. Based on the TL-circuit model we derive exact analytic formulas for a recursive algorithm which allows direct calculation of mode delay and dispersion. We demonstrate this technique by calculating the fundamental mode dispersion for step, triangular, and linear chirp optical fiber refractive index profiles. The accuracy of the numerical results is also examined. The proposed algorithm computes dispersion directly from the propagation constant without the need for curve fitting and subsequent successive numerical differentiation. It is exact, rapidly convergent, and it results in savings for both storage memory and computing time. [ABSTRACT FROM AUTHOR]

without adaptive optics high-power lasers suffer either from poor beam quality or limited power ranges. A laser can be forced to operate on its stability limit by self-adaptive overcompensation resulting in constant and good beam quality over a large power range. With this technique, the brightness of a Nd:YAG laser was increased by almost an order of magnitude despite highly aber-rated thermal lens in the laser rod. [ABSTRACT FROM AUTHOR]

This article discusses the illustration motifs for effective medical volume illustration. The enormous amount of 3D data generated by modern scientific experiments, simulations, and scanners exacerbates the tasks of effectively exploring, analyzing, and communicating the essential information from these data sets. The expanding field of biomedicine creates data sets that challenge current techniques to effectively communicate information for use in diagnosis, staging, simulation, and training. In contrast, medical illustration succinctly represents essential anatomical structures in a clear way and is used extensively in the medical field for communicative and illustrative purposes. The fundamental goals of visualization are insight and communication; therefore, visualizations must allow a rich and varied repertoire for clear and concise depictions of complex phenomenon to aid in the task of sense making. The visualization challenge then becomes providing a diverse set of tools that allows for a wide variance of approaches to the information, one that not only allows you to see the information, but also facilitates thinking about the information. INSET: Pervious Work..

This article reviews the current status and technologies of all-optical XOR gates. Various schemes with semiconductor optical amplifiers, particularly those associated with interferometric structures, are discussed and compared. Finally, the applications of all-optical XOR gates to emerging networks are explored, and the future direction is outlined. [ABSTRACT FROM AUTHOR]

We present a detailed theoretical study of a vertical- cavity surface-emitting laser (VCSEL) with two optically coupled, active cavities. The study is based on a rate-equation model written for carriers and photons under steady-state conditions. The model allows one to determine all the relevant parameters-carrier densities, gains, and output powers-starting from two input parameters: the injection currents in each cavity. The system of equations is solved for different operating regimes of the device and the results provided by the model are shown to be in very good qualitative and quantitative agreement with the experimental data. [ABSTRACT FROM AUTHOR]

A tunable highpower cladding-pumped neodymium- doped aluminosilicate fiber laser is demonstrated. The maximum power reached was 2.4 W with a slope efficiency of 41 % and a threshold pump power of 1.68 W, both with respect to launched pump power, when cladding pumped by two 808-nm diode pump sources at both fiber ends. The dependence of the tuning range on the fiber length is investigated. The tuning range changed from 922 to 942 nm for a 25-m-long fiber to 908-938 nm with a 14-m-long fiber, because of reabsorption effects. The output llnewidth was 0.26 nm in a diffraction-limited beam. Operation on the challenging 0.9-μm three-level transition in neodymium-doped double-dad fiber laser was facilitated by a W-type core refractive index profile. This filtered out the unwanted and competing strong transition at 1.06 μm while guidance of 0.9 μm remained intact. [ABSTRACT FROM AUTHOR]

With the advances in imaging technologies for robot or machine vision, new imaging devices are being developed for robot navigation or image-based rendering. However, to satisfy some design criterion, such as image resolution or viewing ranges, these devices are not necessarily being designed to follow the perspective rule and, thus, the imaging rays may not pass through a common point. Such generalized imaging devices may not be perspective and, therefore, their poses cannot be estimated with traditional techniques. In this paper, we propose a systematic method for pose estimation of such a generalized imaging device. We formulate it as a nonperspective n point (NPnP) problem. The case with exact solutions, n = 3, is investigated comprehensively. Approximate solutions can be found for n > 3 in a least-squared-error manner by combining an initial-pose-estimation procedure and an orthogonally iterative procedure. This proposed method can be applied not only to nonperspective imaging devices but also perspective ones. Results from experiments show that our approach can solve the NPnP problem accurately. [ABSTRACT FROM AUTHOR]

We grew good-optical-quality KGd(WO4)2 single crystals doped with erbium and ytterbium ions at several concentrations of dopants using the top-seeded-solution growth slow-cooling method (TSSG). We performed the spectroscopic characterization of this material related to the 1.5μ infrared emission of erbium which is interesting for laser applications. To do this, we carried out polarized optical absorption at room temperature (RT) and at low temperature (6 K) and performed luminescence studies of the emission and lifetime. We obtained the 1.5-μm emission of erbium after selective laser pump ex- citation of the ytterbium ion and energy transfer between the two ions. The maximum emission cross section for 1.5 μm was about 2.56 × 10-20 cm² for the polarization of light with the electric field parallel to the Nm principal optical direction. This value was higher than for other erbium-doped materials with application in solid-state lasers such as LiYF4 : Er(YLF : Er), Y3Al5O12 : Er(YAG : Er),YAIO3 : Er, and Al2O3 : Er. [ABSTRACT FROM AUTHOR]

In this paper, we present an experimental demonstration of a high-quality optical pulse train generation at 80 Gb/s. The successful operation was achieved via two steps. In the first step, an ultrastable 2-ps (FWHM), 40-Gb/s pulse train was generated using the technique of fourth-order rational harmonic mode locking. The mode-locked laser was stabilized using a regenerative-type base-line extraction feedback technique. In the second step, an external fiber loop mirror consisting of several meters of polarization-maintaining fiber was used to double the repetition rate from 40 to 80 Gb/s. The output of the SO-Gb/s pulse train shows very small pulse-to-pulse amplitude fluctuation with good long-term stability. [ABSTRACT FROM AUTHOR]

We present the results of an experimental investigation of the transfer characteristics of a fiber ring resonator for various values of the resonator finesse. In particular, we measure the spectral dependence of the intensity transmission and the induced phase shift in the undercoupled, critically coupled, and over- coupled regimes. We also demonstrate tunable optical (true time) group delay via a fiber ring resonator and show that a high finesse is unnecessary. Our laboratory results are in excellent agreement with theoretical predictions. [ABSTRACT FROM AUTHOR]

New RCS data on two spheres in rotation are presented. From the simple geometry, the results allow us to verify both the cross-range and down-range distance scales in imaging. With the known RCS of the individual spheres, we find that it is feasible to calibrate the image RCS scale to dBsm, provided care is taken to mitigate the shadowing and sidelobe effects. [ABSTRACT FROM AUTHOR]

Many recent investigations of micromachining with lasers, in vacuum and in ambient air environments, have demonstrated the improvements possible when using femtosecond-duration laser pulses compared with long laser pulses. There are obvious practical advantages for rapid micromachining in ambient air conditions. However, the maximum laser intensity and repetition rate are then eventually limited by the avalanche breakdown and nonlinear effects in the air through which the focused laser beam must propagate both outside the work piece and within the structure that is being machined. This paper investigates these limits in femtosecond deep hole drilling at high laser intensities in silicate glasses. In particular, it shows how nonlinear optical effects, particularly self-focusing, can dramatically affect hole shape and the rate of penetration daring deep hole drilling. The experiments described here demonstrate how nonlinear Kerr focusing of femtosecond laser pulses occurs during propagation of intense femtosecond laser pulses through the atmosphere within the machined channel at powers levels significantly below the critical power for self-focusing in ambient air. [ABSTRACT FROM AUTHOR]

A quantum theory for the noise of optical pulses in actively mode-locked lasers is presented. In the presence of phase modulation and/or group velocity dispersion, the linear operator that governs the time evolution of the pulse fluctuations inside the laser cavity is not Hermitian (or normal) and the eigenmodes of this operator are not orthogonal. As a result, the eigenmodes have excess noise and the noise in different eigenmodes is highly correlated. We construct quantum operators for the pulse photon number, phase, timing, and frequency fluctuations. The nonorthogonality of the eigenmodes results in excess noise in the pulse photon number, phase, timing, and frequency. The excess noise depends on the frequency chirp of the pulse and is present only at low frequencies in the spectral densities of the pulse noise operators. [ABSTRACT FROM AUTHOR]

Presents the N-queen lattice technique to spatially subsample a block of pixels. Function of pixel decimation; Patterns by which pixel decimation can be achieved; Measurement of the sampling lattice.

We demonstrated a 256 × 256 voltage-tunable two-color corrugated quantum-well infrared-photodetector focal plane array. The detector operation is based on photocurrent asymmetry in a double-superlattice quantum well structure. By using a broadband corrugated light coupling scheme, we obtained a quantum efficiency of 24% in the mid-wave (MW) band and 26% in the long-wave (LW) band without AR coating. Operating at 50 K, the measured noise equivalent temperature difference is 27 mK at 33-ms integration time for the MW and 90 mK at 2 ms for the LW with f/2.44 optics. The NETD operability values are 98.4% and 95.9%, respectively. [ABSTRACT FROM AUTHOR]

A three-laser heterodyne system was used to frequency measure 11 previously observed optically pumped far-infrared (FIR) laser emissions of CHD2 OH. These newly measured frequencies have fractional uncertainties of ±2 × 10-7 and correspond to laser wavelengths ranging from 47.8 to 238.0 μm. The pump laser offset frequency was measured for 15 CHD2OH FIR laser emissions. [ABSTRACT FROM AUTHOR]

An optical tomographic diagnostic instrument has been fielded at the Dual-Axis Radiographic Hydrodynamic Test Facility at Los Alamos National Laboratory. Four optical lines of sight create projections of an image of an electron beam on a Cerenkov target, which are relayed via optical fiber to streak cameras. From these projections, a reconstruction algorithm creates time histories of the beam’s cross section. The instrument was fielded during and after facility commissioning, and tomographic reconstructions reported beam parameters. Results from reconstructions and analysis are noted. [ABSTRACT FROM PUBLISHER]