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  • Volume 47, Issue 5

    • Volume 47, Issue 5

    Lasers & Sources

    ZnO nanorod LED emits broadband blue-white light

    John Wallace
    May 1, 2011
    Zinc oxide (ZnO) is a semiconductor with a bandgap in the UV, making it potentially useful as an alternative to gallium nitride for blue- and UV-emitting laser diodes and LEDs...
    Test & Measurement

    False alarm raises integrity of LIGO report

    Gail Overton
    May 1, 2011
    Since beginning operations in 2002, the more than 800 scientists working on the Laser Interferometer Gravitational-Wave Observatory have been anxious to observe tiny variations...
    Optics

    Strain-based second-harmonic generation in Si is tested in detail

    John Wallace
    May 1, 2011
    Ideally, CMOS-compatible integrated silicon (Si) photonic circuits would contain microscopic analogues of all bulk-optic components such as emitters, receivers, and lenses.
    Optics

    Injection locking increases InP disc-laser modulation rate

    Gail Overton
    May 1, 2011
    Although silicon-on-insulator (SOI) modulators have been demonstrated for future on-chip integrated-photonics interconnect architectures, they require an external laser source...
    Research

    Femtosecond laser writes singlemode waveguides in zinc phosphate glass

    John Wallace
    May 1, 2011
    By directly writing with a femtosecond laser, researchers at the University of California–Davis and the Missouri University of Science and Technology (Rolla, MO) have tested several...

    More content from Volume 47, Issue 5

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    Optics

    ASPHERES: Fabrication choices impact IR asphere design

    Gregg Fales
    May 1, 2011
    The choice of infrared optical material for an asphere determines how it can be fabricated; this in turn determines which design options are available, such as the addition of...
    A grayscale diagram shows the results of NIST randomness tests done on a bitstream produced by a SLED-based true random-number generator (RNG) including a time-delayed XOR operation. The chart gives the number of failures out of 1000 trials for the different tests (the one exception is for the random-excursion variant test, which shows results for 561 trials). The RNG passed all tests.
    Research

    CRYPTOGRAPHY: SLED-based true random-number generator is scalable in output

    John Wallace
    May 1, 2011
    A true random-number generator (RNG) developed by a group of Chinese and American researchers can generate two simultaneous, independent 10 Gbit streams of random bits from a ...
    (Illustration courtesy of X. Gu et al. [6])
    FIGURE 1. In the XFROG apparatus a sum-frequency-generation crystal cross-correlates the two pulses. The crystal is angle-dithered to generate the sum frequencies of all frequencies in the continuum (top). In this example of measured and retrieved XFROG traces of an ultrabroadband continuum with a TBP of >1000, the retrieved trace does not agree with the measured trace, indicating that something is wrong. In this case, what’s wrong is not the measurement but the train of pulses being measured: Every pulse in the train is different, violating the universal scientific-measurement assumption that all objects averaged over during a measurement are identical. Fortunately, the XFROG measurement reveals this fact at the same time that it yields a typical pulse in the train (middle). The measured continuum pulse is also shown in the time and frequency domains (bottom).
    Test & Measurement

    ULTRAFAST PULSE CHARACTERIZATION: Optical complexity challenges pulse-measurement methods

    May 1, 2011
    Techniques for measuring simple ultrashort laser pulses are often unable to temporally characterize extremely complex pulses—such as shaped pulses, ultrabroadband continua, and...
    1304qa Chang New
    Executive Forum

    Business Forum: How can a startup avoid the 'valley of death'?

    Milton Chang
    May 1, 2011
    Can you offer some suggestions on how to bridge the ‘valley of death’ gap startup companies face?
    (Courtesy of the University of Shanghai for Science and Technology and Swinburne University of Technology)
    In the normal Doppler effect (a) for materials with refractive index greater than zero, the detected frequency f’ for a wave source moving toward the detector is shifted to shorter wavelengths (blue shift), and red-shifted for a source moving away. The opposite shift occurs (b) for a negative-refractive-index metamaterial—the inverse Doppler effect.
    Optics

    NEGATIVE-INDEX MATERIALS: Metamaterial reveals inverse Doppler effect

    Gail Overton
    May 1, 2011
    When a wavelength source and an observer are moving in relation to each other, a fundamental frequency shift is observed called the Doppler effect due to wave compression or extension...
    (Courtesy of H. Tao et al. [2])
    FIGURE 1. Unit cell of a terahertz absorber, with electric resonator element on top of a polyimide spacer, and a cut wire on a gallium-arsenide substrate at bottom for magnetic coupling (a). Experimental absorption results in blue compared with simulation results in red (b).
    Optics

    PHOTONIC FRONTIERS: METAMATERIALS: Optical metamaterials seek real-world applications

    Jeff Hecht
    May 1, 2011
    Like the laser half a century ago, metamaterials sometimes seem to be a solution looking for a problem. Now developers are working on a first round of applications in niches that...
    An integrated optical magnetic-field sensor consists of a Mach-Zehnder interferometer on LiNbO3 with a doubly loaded loop antenna. It has a frequency response ranging from 2 kHz to 9 GHz (a) and a dynamic range of 98 dB (b).
    Test & Measurement

    INTERFEROMETERS: Integrated optical sensor measures dynamic magnetic fields

    John Wallace
    May 1, 2011
    Magnetic-field sensors that measure the magnetic portion of electromagnetic fields (as opposed to sensors that measure static magnetic fields) are valuable for determining problems...
    (Courtesy of Mitsubishi Electric)
    FIGURE 1. Diamond Vision LED displays use two optical innovations to improve performance for ultralarge displays: “Quad Dot Pattern” technology (a) in which a color pixel is created from four dots—two red, one green, and one blue—in a configuration that allows a screen processor to share dots between adjacent pixels to create a “dynamic” pixel for increased viewing resolution; and individual shaders for each color LED (b) that give true colors when viewing at oblique angles, rather than multishading architectures that can obscure whole LED colors in a group, radically changing the color appearance.
    Detectors & Imaging

    PHOTONICS APPLIED: DISPLAYS: Digital signage: What will they think of next?

    Gail Overton
    May 1, 2011
    While many consumer display technologies for laptops, cell phones, and televisions have reached maturity, public displays and digital signage may have the largest growth potential...
    (Courtesy of NIICT)
    A seven-core optical fiber carries 15.6 Tbit per core, for 109 Tbit/s through the entire fiber before forward-error correction.
    Research

    FIBER-OPTIC COMMUNICATIONS: OFC postdeadline highlights include 100 Tbit fiber transmission

    Jeff Hecht
    May 1, 2011
    Demonstrations of high-speed fiber-optic transmission reached a major milestone at the March 10 postdeadline session of this year’s Optical Fiber Communications Conference.
    FIGURE 1. A conceptual drawing shows a hyperspectral camera today (a) and a new integrated system (b) in which an objective lens is combined with the image sensor and a hyperspectral filter structure that is directly post-processed on top of the image sensor.
    Detectors & Imaging

    MULTISPECTRAL/HYPERSPECTRAL IMAGING: CMOS takes hyperspectral imaging beyond the laboratory

    May 1, 2011
    To enable the transfer of applications from the lab to the industry, a new hyperspectral camera module based on CMOS-compatible production techniques has been developed that eliminates...
    Cut-away schematic of an organic photodetector fabricated on a silicon AFM tip shows the organic thin-film and electrode structure (a). Scanning of an aperture in a silver film back-illuminated at λ = 475 nm produces simultaneous topographic and optical (photocurrent) signals (b) and (c). The detector photocurrent measured during the scan of the dotted line in (c) is shown in (d).
    Detectors & Imaging

    ORGANIC PHOTODETECTORS: Thin-film organics bring integrated optical detection to AFM probes

    May 1, 2011
    Advances in the fabrication of organic thin-film-based photodetectors and their combination with atomic force microscopy probes enable simultaneous high-resolution optical and...
    (Courtesy of Zhanshan Wang)
    The thermal absorption of fused-silica substrates were measured before cleaning (a), after cleaning using process 1 (b), and after cleaning using process 2 (c). As can be seen, process 2 was more effective.
    Research

    OPTICS FABRICATION: Ultrasound cleaning technique for laser substrate depends on material

    John Wallace
    May 1, 2011
    Manufacturing a functional high-power laser optical component requires great care in every step. Even a flawless optical substrate is of no use if it hasn’t been cleaned adequately...
    (Courtesy of Michael Grogan)
    FIGURE 1. A scanning-electron micrograph shows the cleaved endface of a hollow-core PCF used to guide and compress 540 nm pulses (a). The core diameter is 5.6 μm. The irregularity of some holes in the cladding demonstrates the difficulty of fabricating this fiber due to runaway variations in hole size during the draw. The damage around the core was caused during the fiber cleave; although the fiber as a whole is robust, the individual struts are extremely thin. Despite this, the coupling efficiency into this fiber is still greater than 60%. (Courtesy of Brian Mangan). The output of a HC-PCF transmitting ultrashort green pulses is seen on a white piece of paper, revealing the fiber’s high-quality far-field mode profile (b).
    Fiber Optics

    SPECIALTY FIBERS: Hollow-core fiber delivers ultrafast visible pulses

    May 1, 2011
    The capability of hollow-core photonic-crystal fiber to transmit ultrahigh-power femtosecond pulses without distortion has been extended from the infrared to the visible; compression...
    FIGURE 1. A new wafer-scale etching technique can create refractive micro-optic elements in calcium fluoride.
    Lasers & Sources

    UV OPTICS: Calcium fluoride micro-optics improve DUV excimer laser systems

    May 1, 2011
    Using non-traditional etching techniques, it is possible to fabricate diffractive/refractive calcium-fluoride (CaF2) micro-optics for deep-UV excimer laser systems that can increase...
    (Courtesy of Harvard University)
    Isotope-ratio measurements can be used to distinguish between different sources of carbon in the atmosphere. A precision better than 1‰ is needed for accurate measurements, and the integrated-cavity-output spectroscopy (ICOS) instrument is capable of 0.1‰ precision for a 200 s measurement time period.
    Test & Measurement

    CAVITY-RINGDOWN SPECTROSCOPY: ICOS isotope-ratio measurement sheds new light on climate change

    Gail Overton
    May 1, 2011
    The dramatic decrease in Arctic sea ice in the summer of 2007 was not predicted, and according to some scientists, not well characterized in scientific models.