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  • Volume 44, Issue 11

    • Volume 44, Issue 11

    Th 299304
    Research

    Silicon rods demonstrate supercollimation in the infrared

    Nov. 1, 2008
    Supercollimation, the propagation of light without diffraction, uses the properties of photonic crystals to transmit signals over centimeter-scale distances—ideal for integrated...
    Th 299305
    Detectors & Imaging

    Tiny nanowires make sensitive photodetectors

    Nov. 1, 2008
    Silicon (Si) nanowires are attractive as photodetectors for wavelengths ranging from ultraviolet (UV) to infrared because of their ability to trap carriers at the surface with...

    More content from Volume 44, Issue 11

    (Courtesy of Polymer Optical Fiber Application Center, Nürnberg)
    FIGURE 1. A prototype POF liquid-level sensor (left) works by exploiting the refractive-index difference of light in air versus a liquid. The sensor consists of a bundle of fibers (lower right) illuminated by a red light-emitting diode (LED) and connected to a low-cost CCD camera. A computer measures the intensity per fiber and displays the liquid level as a bar (upper right).
    Fiber Optics

    FIBER FOR CONSUMER APPLICATIONS: New fiber designs extend the reach of short-range POF

    Nov. 1, 2008
    Polymer optical fiber is benefiting from new modulation techniques and polymer designs that are extending data rates to 100 Gbit/s and improving POF performance for sensors, data...
    FIGURE 1. An example of a complex optical system shows multiple folds, wavelengths, and beam paths.
    Positioning, Support & Accessories

    ELECTRO-OPTICAL DEVICES: Novel methods simplify alignment of complex electro-optical systems

    Nov. 1, 2008
    Alignment of electro-optical devices with multiple paths, multiple sources, off-axis elements, tight tolerances, or difficult components can be simplified through well-known tools...
    FIGURE 1. Ellipsometric fitting of the experimental data (cross-hatched lines) and model (solid lines) is improved when a thin interface is included (right side) for a SIMOX structure.
    Test & Measurement

    THIN-FILM METROLOGY: Innovations in ellipsometry facilitate thin-film analysis

    Nov. 1, 2008
    An advanced thin-film metrology tool based on spectroscopic ellipsometry and dedicated to the measurements of blank and patterned wafers is designed to reduce the need for modeling...
    (Courtesy of Northwestern University)
    The cross section of a hybrid inverted green-emitting LED shows its ZnO top layer, its InGaN MQW active layer, and its GaN bottom layer. Only the bottom layer, which is deposited before anything else, requires fabrication at temperatures high enough to damage InGaN.
    Lasers & Sources

    LIGHT-EMITTING DIODES: ZnO does away with green-LED problem

    John Wallace
    Nov. 1, 2008
    While blue and red LEDs can be made to shine brilliantly and have a long life, high-brightness green LEDs tend to die early.
    (Courtesy of the University of Kaiserslautern)
    Black silicon consists of needle-shaped structures created on the surface of silicon through high-energy irradiation or chemical treatment (top); the absorptive structure can have many applications, including being used as a source of terahertz radiation. The silicon was intentionally damaged (bottom) to confirm that the needle structure was indeed the cause of terahertz emission.
    Research

    TERAHERTZ TECHNOLOGY: Black silicon emits terahertz radiation

    Gail Overton
    Nov. 1, 2008
    Treating silicon with repeated high-energy laser pulses or through etching in a plasma creates nanosize structures on its surface, rendering the silicon black in color and able...
    (Courtesy of F. Hossain)
    FIGURE 1. Ab initio density functional theory determines the orbital isosurfaces for the nitrogen-vacancy center (left) and NE8 (right) center in diamond.
    Research

    QUANTUM DEVICES: Diamond technology enables practical single-photon sources

    Nov. 1, 2008
    Optically active color centers in diamond have been found to exhibit attractive optical properties that have paved the way to the realization of practical sources of single-photon...
    FIGURE 1. The beam within the laser module of the nanoparticle tracking analysis system passes through a sample.
    Test & Measurement

    NANO ANALYSIS: Nanoparticle tracking system analyzes polydispersed samples

    Nov. 1, 2008
    The ability to see nanoparticles directly and individually allows a nanoparticle tracking analysis system to analyze samples with particles of varying sizes and shapes.
    (Courtesy of the University of Toronto)
    The wavelength spectrum of a Fourier-domain modelocking laser shows a sweeping range of 112.2 nm with a full-width-half-maximum value of 95.3 nm. The 62.6 kHz sweeping frequency will improve performance of OCT test instrumentation.
    Optics

    FIBER LASER SOURCES: High-power swept-laser source targets OCT

    Gail Overton
    Nov. 1, 2008
    Fourier-domain optical-coherence tomography (OCT) is now being widely used for biomedical imaging with a resolution of several micrometers.
    FIGURE 1. Ultraviolet (UV) detectors can be classified into several types, depending upon the mechanism of detection.
    Detectors & Imaging

    UV DETECTORS: Nitride-based UV detectors improve photodetection

    Nov. 1, 2008
    Compared to ultraviolet detectors based on traditional semiconductors like silicon and gallium arsenide, nitride-based UV detectors have improved insensitivity to visible and ...
    (Courtesy of Fianium)
    FIGURE 1. A comparison of the visible spectral regions of new (upper spectrum) and conventional (lower spectrum) supercontinuum sources after dispersion through a prism demonstrates the extent of additional blue and UV spectral components achieved using the latest PCF developments.
    Fiber Optics

    SUPERCONTINUUM SOURCES: New white-light supercontinuum sources have no blue deficiency

    Nov. 1, 2008
    By changing the air-filling fraction of the photonic-crystal fibers used in white-light supercontinuum sources, the traditional “blue deficiency” of such sources is eliminated...
    FIGURE 1. When testing spherical optics, a null is easily achieved using standard reference optics (left). Testing an asphere in the same setup, however, results in a non-null test wavefront (center). The addition of auxiliary optics, which correct for the (nominal) aspheric portion of the test wavefront, produces a null (right).
    Optics

    NULL OPTICS: Approaches to aspheric metrology become more diverse

    Nov. 1, 2008
    Null optics allow mild to strong aspheres to be interferometrically tested. As an alternative, subaperture-stitching interferometry measures mild to moderate aspheric surfaces...
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    Fiber Optics

    Asymmetric optical potential barrier becomes Maxwell’s demon

    Nov. 1, 2008
    The hypothetical Maxwell’s demon opens and closes a tiny trapdoor dividing two containers of gas to shuttle atoms one way without exerting effort, raising the number of atoms ...
    FIGURE 1. Negative refraction bends light in the direction opposite from normal (positive) refraction. Energy flows in the same direction in a negative-index material as in one with a positive index, but light waves flow in the opposite direction, as shown at bottom.
    Optics

    PHOTONIC FRONTIERS: NEGATIVE-INDEX-MATERIALS: Negative-indexmaterials are on positive track

    Jeff Hecht
    Nov. 1, 2008
    Fabrication of three-dimensional metamaterials with negative refractive index at optical wavelengths has opened the way to dramatic new types of optics, such as “superlenses.