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  • Volume 43, Issue 2

    • Volume 43, Issue 2

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    Optics

    Hubble and ground-based telescopes map dark matter

    Feb. 1, 2007
    An international team of astronomers using NASA’s Hubble Space Telescope has created the first three-dimensional map of the large-scale distribution of dark matter.

    More content from Volume 43, Issue 2

    Driven by an actuator (top, gray), two pusher rings (gold and violet) deform a flat mirror into a paraboloid, compensating for thermal-lens effects occurring in a high-energy-laser rod amplifier. The focal length of the mirror can be varied from infinity down to 5 m (bottom). The interferometrically measured wavefront profile has the desired paraboloidal shape (bottom, 3-D color plot).
    Optics

    LASER OPTICS: Deformable thermal-lens-correcting mirror has single actuator

    John Wallace
    Feb. 1, 2007
    To counter thermal lensing in high-energy-laser rod amplifiers, researchers at Sandia National Laboratories (Albuquerque, NM) have developed a deformable mirror that does one ...
    A card-to-backplane optical interconnect uses an array-waveguide evanescent coupler (AWEC) to connect the card signal directly to the backplane, a more cost-effective technique that eliminates the need for the micromirrors that are typically required to make the 90º turn. Preliminary testing demonstrates operation above 2.5 GHz for the AWEC ribbons.
    Research

    OPTICAL INTERCONNECTS: Flexible evanescent coupler eases backplane connections

    Gail Overton
    Feb. 1, 2007
    Interconnects for card-to-backplane connections and motherboards will soon be required to handle multigigahertz speeds as computing power increases; however, electronic interconnects...
    FIGURE 1. Piezoelectric crystal increases in length L + ΔL and decreases in diameter D + ΔD (ΔD is negative) with an applied voltage V (top, left). Stacked piezoelectric elements increase total displacement for voltage V applied in parallel to each element (top, right). A lever mechanism extends piezoelectric displacement into the 10s or 100s of microns (bottom).
    Positioning, Support & Accessories

    POSITIONING SYSTEMS: Piezoelectric positioners address broad range of tasks

    Feb. 1, 2007
    Accurate positioning in laser and photonics applications generally relies upon converting an applied voltage into a very accurate displacement.
    In an experimental setup for position detection using hyperacuity (top), a point source at infinity or on an edge at a finite distance is used as the object within the field of view of an artificial apposition compound eye (APCO; bottom). Rotating the ensemble of the APCO, the microscope objective, and the CCD camera simulates object movement.
    Research

    IMAGING OPTICS: Artificial compound eye applies hyperacuity

    Gail Overton
    Feb. 1, 2007
    Researchers at the Fraunhofer Institute for Applied Optics and Precision Engineering (IOF) and at Friedrich Schiller University Jena (both in Jena, Germany), are applying hyperacuity...
    FIGURE 1. The operation of the high-throughput three-dimensional detector (H33D) begins with a pulsed laser to excite the fluorescence of a sample. Fluorescence photons are collected by the imaging optics and interact with the photocathode, creating one photoelectron per photon that is amplified by an opposed multichannel plate to generate an electron cloud (cone shape). The position of the cloud is determined by a position-sensitive cross-delay line anode, in which charges propagate through the lines and are collected at both ends. Timing electronics convert the differences in arrival time into position information and the four photon coordinates (laser pulse nanotime τ, position x, y, and macrotime T) are processed and stored by a computer. In the setup, the fixed time delay is δ, signal-propagation velocity v > 1 mm/ns, and the sensitive area has a diameter of 1 inch.
    Detectors & Imaging

    DETECTORS FOR MICROSCOPY: Next-generation 3-D detector improves single-molecule imaging

    Feb. 1, 2007
    A high-throughput three-dimensional detector combines the advantages of wide-field detectors and high-temporal-resolution point detectors, proving instrumental for single-molecule...
    Continuous demagnetization cools chromium atoms in an optical dipole trap while minimizing the loss of atoms. The black squares show the evolution of temperature (top) and the number of atoms in the trap (bottom) as the magnetic field is decreased from 250 to 50 mG; the red circles are the same quantities when the field is kept constant.
    Research

    LASER COOLING: Cooling of Cr atoms by adiabatic demagnetization is loss-free

    Uwe Brinkmann
    Feb. 1, 2007
    Laser cooling of atomic and molecular gases has helped scientists explore the boundaries of low-temperature physics—for example, by creating Bose-Einstein condensates (whose uses...
    FIGURE 1. Aspheric subaperture-stitching interferometry can be used to measure the surface figures of aspheres such as this ellipsoid (conic), which has a 100 mm aperture diameter, a base radius of -226 mm, and approximately 12 µm of aspheric departure. The asphere is fabricated from lightweighted silicon carbide with silicon cladding.
    Optics

    ASPHERIC OPTICS: Distributing aspheric surfaces brings down cost

    Greg Forbes
    Feb. 1, 2007
    Distributed, mild aspheric surfaces and subaperture-stitching interferometry combine to form a cost-effective approach to fabricating aspheric optics.
    The ratios of group (vg) and phase (vp) velocities to the speed of light (c) of a surface-plasmon polariton on a metal nanorod vary as functions of gain (top left), frequency (bottom left), and radius (top and bottom right).
    Research

    PLASMONICS: Small gain yields great control

    Hassaun A. Jones-Bey
    Feb. 1, 2007
    Optical gain in subwavelength waveguides is generally used for compensating losses.
    Laser processing of the back side of a solar cell creates an emitter and base region (inset shows a scanning-electron micrograph of a structured silicon surface with separated contact levels). A wet chemical-etching step removes silicon crystal damage (due to laser ablation) that can reduce carrier lifetime, resulting in a highly efficient solar cell with greater than 22% conversion efficiency.
    Research

    PHOTOVOLTAICS: Laser processing yields solar cells with 22% efficiency

    Gail Overton
    Feb. 1, 2007
    Solar cells made from crystalline silicon (Si) dominate the solar photovoltaic market.
    FIGURE 1. In a multiphoton-microscopy image of mature glomerulus from an adult rat, podocytes are labeled with antivimetin (brown) and the nuclei with DAPI (blue). This image was taken using a Spectra-Physics femtosecond Ti:sapphire laser (Mai Tai) tuned to 800 nm.
    Optics

    OPTOELECTRONIC APPLICATIONS: BIOMEDICAL IMAGING - Multiphoton microscopy takes biologists into uncharted territory

    Kathy Kincade
    Feb. 1, 2007
    Confocal microscopy may be the current standard for studying live cells, but multiphoton is the rising star.
    A study undertaken by TeraView and the FDA looked at coating-thickness variations on Internet-sourced pharmaceutical products, revealing large variations in tablet-coating thickness within the same tablet and between tablets.
    Detectors & Imaging

    3-D MAPPING: Terahertz technology detects counterfeit drugs

    Bridget Marx
    Feb. 1, 2007
    Researchers at TeraView (Cambridge, England) are using terahertz technology to help regulatory authorities, law-enforcement agencies, and the pharmaceutical industry screen for...
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    Research

    Nanophotonic coaxial waveguid channels visible light

    Feb. 1, 2007
    Physicists at Boston College (BC; Chestnut Hill, MA) have shown that a nanoscale coaxial waveguide can guide visible light.
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    Lasers & Sources

    LASER MARKETPLACE 2007: Diode-laser market takes a breather

    Feb. 1, 2007
    The diode-laser market was mixed in 2006, with revenues in some categories increasing significantly, and those in other categories showing substantial declines.
    A scanning-electron micrograph reveals uniform diameters and smooth surfaces in p-type ZnO nanowire arrays.
    Lasers & Sources

    NANOTECHNOLOGY: Complementary zinc oxide nanowires may yield cheaper LEDs and solar cells

    Hassaun A. Jones-Bey
    Feb. 1, 2007
    Before the development of gallium nitride (GaN) blue light-emitting-diodes (LEDs) by Shuji Nakamura, zinc oxide (ZnO) was broadly studied as a possible material for blue emitters...