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  • Volume 45, Issue 6

    • Volume 45, Issue 6

    FIGURE 1. A 12-bar conduction-cooled QCW diode stack proved the right choice for the system; its nominal stack geometry enables a beam profile of 6 x 0.5 mm (left). A number of deviations from nominal (reference) positions are common (right).
    Lasers & Sources

    BEAM ANALYSIS: Beam shaping improved diode-laser performance

    June 19, 2009
    While high-power diode lasers are attractive for applications in which size and efficiency matter, other inherent characteristics have limited their use. Now the European Space...
    Th Nano Y 01
    Research

    Nanograined Y2O3 ceramic transmits as well as single crystal

    June 1, 2009
    Certain sesquioxides, such as yttrium sequioxide (Y2O3), would make excellent high-power laser hosts but for one drawback: their melting point is so high that single laser crystals...
    Fiber Optics

    Radio-over-fiber/WDM scheme uses all-optical upconversion

    June 1, 2009
    To allow optical fibers to transmit both telecom (1550 nm) wavelength-division-multiplexed (WDM) signals and millimeter-wave radio signals to serve broadband wireless communication...
    Fiber Optics

    Ultrafast photonic device integrates optical intensity signals

    June 1, 2009
    The quickest information-processing circuits in the future will be photonic, rather than electronic.
    Fiber Optics

    Higher-order modes limit pulse broadening in ultrafast fiber lasers

    June 1, 2009
    The ytterbium (Yb) and erbium (Er) fibers used in ultrafast fiber lasers are, like any other optical fibers, subject to chromatic dispersion, which results in pulse broadening...

    More content from Volume 45, Issue 6

    (Courtesy of NIST and OFS Laboratories)
    A vibration-immune fiber-laser frequency comb is based on a femtosecond fiber figure-eight laser phase-locked to a 1560 nm fiber-laser source with sub-hertz residual linewidth. Black lines represent wire and brown lines fiber. The beat spectrum of this optical lock is also shown. The beat frequency of both the optical (f1560) and the carrier-envelope offset (CEO) lock was taken while the setup was subjected to vibrations at more than 1 g, and reveals that the comb remains phase-locked over the whole measurement.
    Test & Measurement

    OPTICAL METROLOGY: Fiber-laser-based frequency comb nears vibration immunity

    Gail Overton
    June 1, 2009
    With applications in distance metrology, microwave generation, spectroscopy, and optical-waveform measurement, frequency combs have moved well beyond their initial application...
    (Courtesy of MIT)
    A monolithically integrated Ge-on-Si device (top) exhibits direct-bandgap luminescence at room temperature. The electroluminescence (spectrum at bottom) increases in intensity as a function of electrical-injection current (inset).
    Optics

    SILICON PHOTONICS: Ge-on-Si emitter moves silicon photonics ahead

    Gail Overton
    June 1, 2009
    The last few years have seen a surge in the development of silicon-based photonic components.
    (Courtesy of Trumpf)
    FIGURE 1. For laser cladding applications, powder blown through a nozzle or nozzles is sintered using heat from the central laser beam.
    Research

    PHOTONICS APPLIED: MATERIALS PROCESSING: Laser additive manufacturing gains strength

    Gail Overton
    June 1, 2009
    The process of using a laser and donor materials for component prototyping and repair—loosely termed “laser additive manufacturing”—is just now gaining widespread adoption, thanks...
    Research

    SCIENCE & TECHNOLOGY EDUCATION: Intel Science Talent Search encourages student excellence and innovation

    June 1, 2009
    Forty finalists in the 2009 Intel Science Talent Search competition spent a week in the nation’s capitol, where they competed for more than $500,000 in awards and scholarships...
    (Courtesy of Sematech)
    FIGURE 1. Usable EUV output power from laser-pumped plasma sources (green squares) currently exceeds that from discharge-pumped plasma sources (gray diamonds).
    Lasers & Sources

    PHOTONIC FRONTIERS: EXTREME-UV LITHOGRAPHY: Extreme-UV lithography struggles to shrink chip features

    Jeff Hecht
    June 1, 2009
    Shorter wavelengths promise higher resolution and smaller features when fabricating semiconductor chips.
    Th Surving 01
    Lasers & Sources

    EUROPEAN REPORT: Surviving the downturn

    June 1, 2009
    The significance of photonics technologies in terms of Europe’s future economic growth cannot be understated.
    (Courtesy of UCLA)
    The STEAM camera was used for real-time imaging of laser ablation (a), revealing multiple two-dimensional (2-D) real-time images with a temporal resolution of 163 ns and shutter speed of 440 ps (b). Changes in sample surface reflectivity due to the laser-induced mass ejection are evident after the excitation pulse hits the sample at 50 ns. The time-sequenced surface reflectivity shows that the time delay between the pulse excitation and the sudden decrease in the surface reflectivity correlates with the ablation process (c); depth profile measurements (d) indicate that the silicon-on-insulator layer was exposed.
    Lasers & Sources

    HIGH-POWER DIODE LASERS: Direct-diode lasers combine to form powerful, high-brightness beam

    John Wallace
    June 1, 2009
    Multikilowatt laser-diode systems typically reach their high output powers through wavelength coupling of a number of individual diode stacks.
    (Courtesy of Vanderbilt University)
    FIGURE 1. In a laser-scanning microscope, data can be gathered either by current integration or by photon counting. Each line (row of pixels) is defined by the line synchronization signal. During the period that a single pixel is scanned (typically a few microseconds defined by the pixel clock), each incident photon will produce a current pulse in the photomultiplier tube (PMT) signal. When the current is integrated, dark events as well as pulse amplitude variation lead to increased noise in the output signal. Alternatively, in photon counting, if the pulses are discriminated (rising above the dotted line), shaped, and then counted, no additional noise is introduced.
    Detectors & Imaging

    SINGLE-PHOTON DETECTORS: Fluorescence microscopy benefits from advances in single-photon detectors

    June 1, 2009
    Recent advances in single-photon-counting detectors can be incorporated in commercial microscope systems to improve fluorescence-signal detection in live-cell imaging.
    (Courtesy of Philips)
    Data from scattering measurements were used to construct these far-field emission patterns of PC LEDs. A PC with a lattice constant of 315 nm and weak photonic coupling emits a relatively simple pattern (top; blue and yellow correspond to TE and TM polarizations from the LED modes), while one with a 250 nm lattice constant and strong photonic coupling creates a much-more-complex pattern (bottom). The light in the complex pattern fills the extraction cone more uniformly.
    Research

    LIGHT-EMITTING DIODES: Photonic-crystal LED has high extraction efficiency

    John Wallace
    June 1, 2009
    In a step toward reaching the ultimate light-extraction efficiency for high-power, high-brightness LEDs, researchers at Philips Lumileds Lighting (San Jose, CA) and Philips Research...
    (Courtesy of Politecnico di Milano)
    FIGURE 1. The layout of a pixel in a 32 × 32 photon-counting camera includes a SPAD detector, front-end quenching circuit, and counter. When a photon triggers the SPAD, the VLQC senses the avalanche, quenches the current, and resets the SPAD (right); the ancillary electronics send a count to the counter.
    Detectors & Imaging

    ADVANCED CAMERAS: Single-photon-counting camera operates at high frame rates

    June 1, 2009
    A 32 × 32-pixel single-photon-counting camera consists of single-photon avalanche diodes with all electronics incorporated within each pixel.
    (Courtesy of ULIS)
    A 17 µm pixel-pitch detector is fabricated using standard CMOS processes for high-definition surveillance applications and has ultralow pixel-defect rates. It is small in size and does not require thermoelectric cooling.
    Detectors & Imaging

    DETECTORS: ULIS launches 17 µm pixel-pitch IR sensor

    Gail Overton
    June 1, 2009
    Detector manufacturer ULIS, a subsidiary of Sofradir and GE Equity, launched a fourth-generation IR detector; the XGA format (1024 × 768), 17 µm pixel-pitch sensor enables high...
    (Courtesy of Exfo)
    A distributed-PMD analyzer measures PMD along a sample fiber-optic link (top), displaying cumulative PMD (bottom; white line) as a function of individual fiber sections along the link.
    Fiber Optics

    FIBER-OPTIC TEST EQUIPMENT: Commercially available analyzer computes distributed PMD

    Gail Overton
    June 1, 2009
    Measurement of the distributed polarization-mode dispersion (PMD) along an optical fiber has been actively researched over the past decade or so, and a number of approaches proposed...
    Optics

    Metamaterial with hyperbolic dispersion is 51 µm thick

    June 1, 2009
    While the idea of a metamaterial-based invisibility cloak is fascinating, transforming the idea into reality is a daunting task.
    Th How To 01
    Test & Measurement

    PRODUCT FOCUS: LASER-BEAM PROFILERS: How to select a beam-profile measurement system

    Valerie Coffey-Rosich
    June 1, 2009
    When choosing a laser-beam profiling system, you’ll need to know a few things about your laser and what you want to measure.
    (Courtesy of Vanderbilt University)
    FIGURE 1. In a laser-scanning microscope, data can be gathered either by current integration or by photon counting. Each line (row of pixels) is defined by the line synchronization signal. During the period that a single pixel is scanned (typically a few microseconds defined by the pixel clock), each incident photon will produce a current pulse in the photomultiplier tube (PMT) signal. When the current is integrated, dark events as well as pulse amplitude variation lead to increased noise in the output signal. Alternatively, in photon counting, if the pulses are discriminated (rising above the dotted line), shaped, and then counted, no additional noise is introduced.
    Detectors & Imaging

    SINGLE-PHOTON DETECTORS: Fluorescence microscopy benefits fromadvances in single-photon detectors

    June 1, 2009
    Optical detectors used in photon-counting mode provide ideal signal-to-noise characteristics (limited by the shot noise).