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  • Volume 55, Issue 07

    • Volume 55, Issue 07

    Test & Measurement

    On-chip laser-based quantum device generates true random numbers

    John Wallace
    July 1, 2019
    A photonic integrated circuit containing two laser diodes whose outputs are interfered and measured produces truly random numbers at gigahertz rates.
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    Spectroscopy

    Mid-IR spectroscopy monitors UV-curable adhesive dynamics

    Gail Overton
    July 1, 2019
    Because many industrial and biological processes require monitoring of spectral events on a range of timescales, QCL-based mid-IR spectrometers can span milli- to microsecond ...
    (Courtesy of Thorlabs)
    FIGURE 1. A spectral transmission curve for a high-LIDT polarizing beamsplitter (PBS) cube made by Thorlabs designed for use at 532 nm has a high polarization selectivity. A similar cube designed for use at 1064 nm is shown in the inset.
    Optics

    Optical Coatings: Coatings for laser optics achieve high LIDT

    John Wallace
    July 1, 2019
    For optics used with high-power and high-energy lasers, a high laser-induced damage threshold (LIDT) is crucial.
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    Commentary

    Fiber sensing

    John Lewis
    July 1, 2019
    Editor in chief John Lewis introduces Laser Focus World’s July 2019 issue, which includes trends in photonics technologies, applications, and markets.
    FIGURE 1. In a schematic of the X-LSQ150B linear stage, measurements are made relative to the reference position indicated between the stage base and the motor.
    Positioning, Support & Accessories

    Photonics Motion Control: Operational strategies mitigate thermal expansion effects on linear positioning systems

    July 1, 2019
    Beyond selecting low-thermal-expansion materials for hardware components, a series of operational procedures can minimize repeatability errors on linear positioning systems caused...

    More content from Volume 55, Issue 07

    Image credit: Zhejiang University
    Doughnut-shaped intensity point spread functions (IPSFs) are compared before (a) and after (c) application of a machine-learning-based adaptive-optic (AO) correction; the IPSF profiles (b, d) along lines I and II are also charted before (blue) and after (magenta) correction.
    Optics

    Machine-learning-based adaptive optics maintain doughnut-shaped beams in scattering media

    Gail Overton
    July 1, 2019
    Using a large number of optical elements and machine learning algorithms, researchers can maintain the focus of doughnut-shaped beams in scattering media - a critical need for...
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    Optics

    Metasurface lens on diamond single-photon quantum source efficiently collects photons

    John Wallace
    July 1, 2019
    A nitrogen-vacancy (NV) diamond produces single photons; a metalens etched into its surface collects them, no microscope needed.
    FIGURE 1. A real laser beam will have a divergence angle (θR) greater than that of an ideal Gaussian beam (θG); the beam’s wavefront is planar in the near field near the beam waist and curved in the far field.
    Lasers & Sources

    Laser Beam Quality: Beam propagation and quality factors: A primer

    Randall Hinton
    July 1, 2019
    Approaches for determining laser beam quality differ for different applications; this summary of best practices covers them all.
    Courtesy of Dingkun Ren, UCLA
    To create a gold grating on a nanowire array (a), the nanowires themselves (vertical projections) were used as shadow masks by depositing the gold at an angle to the surface, resulting in undeposited areas (dark regions). Future nanowire-based separate absorption and multiplication avalanche photodiodes (SAM-APDs) will have faceted nanowires to help relieve lattice-mismatch strain (b).
    Detectors & Imaging

    Short- and mid-wavelength infrared nanowire photodiodes are uncooled

    John Wallace
    July 1, 2019
    Nanowires of InAs and InAsSb on an indium phosphide substrate form room-temperature SWIR or MWIR photodiodes suitable for focal-plane arrays.
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    Lasers & Sources

    Fiber laser delivers 1300 and 1700 nm light simultaneously for three-photon microscopy

    Gail Overton
    July 1, 2019
    The first femtosecond fiber laser that economically delivers both 1300 and 1700 nm laser light simultaneously provides the repetition rate and fluence levels required for emerging...
    FIGURE 1. The transparent zebrafish embryo enables paired patch clamp measurements of spinal neurons and locomotory muscle cells. Two chevron-shaped repetitive segments of tail muscle are shown. The two patch clamp recording electrodes are shown for an individual motoneuron and muscle cell. Only one electrode is visible in the field because placement of the electrodes during formation of whole-cell recording mode is done under very high magnification.
    Test & Measurement

    Neuroscience/Bioimaging: Optomechanics reveals transmitter roles in neuromuscular junctions

    John Wingerd
    July 1, 2019
    A clever optomechanical setup enables researchers to use patch clamp, Ca2+ imaging, and optogenetics to elucidate the roles of various neurotransmitters and correlate them with...
    Courtesy of Chaitanya Kumar, ICFO, and Saher Junaid, DTU Fotonik
    A mid-IR upconversion imager first uses frequency downconversion to generate mid-IR light from a pulsed near-IR laser that can be tuned to different wavelengths; the resulting mid-IR image is then upconverted to the near-IR.
    Detectors & Imaging

    Mid-IR upconversion imaging promises to speed diagnosis

    Barbara Gefvert
    July 1, 2019
    A rotatable lithium niobate upconversion crystal generates phase matching of concentric rings in the object plane, leading to a wide field of view.
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    Detectors & Imaging

    Next-generation gravitational-wave detectors require even better mirror coatings

    Gail Overton
    July 1, 2019
    Compared to the current capabilities of sensitive detector coatings used for gravitational-wave detection on instruments such as LIGO, next-generation coatings with even lower...
    (Image credit: Empa)
    A quantum-cascade-laser (QCL)-based absorption spectroscopy setup measures alcohol in exhaled breath with high-enough accuracy to be used as a metrological standard.
    Test & Measurement

    QCL-based spectroscopy challenges metrological standards for breath alcohol testing

    Gail Overton
    July 1, 2019
    Mid-IR direct absorption spectroscopy using compact quantum cascade lasers removes uncertainties in ethanol measurements in the presence of water, proving its ability to be used...
    (Courtesy of Kyushu University)
    A schematic shows the configuration of an electrically pumped organic laser diode using a film of BSBCz as the gain medium and a silicon dioxide (SiO2) grating as the DFB mechanism.
    Lasers & Sources

    Electrically pumped organic diode laser comes to fruition

    Jeff Hecht
    July 1, 2019
    Narrowline blue laser emission has been reported from an electrically pumped film of the organic substance BSBCz coupled with a distributed-feedback grating.
    FIGURE 1. The basic schematic of a silicon photonics (SiPho) integrated tunable laser includes the waveguides and filter components, a spot-size converter (SSC), and the on-chip tunable laser gain module that is input to the semiconductor optical amplifier (SOA).
    Lasers & Sources

    Tunable Lasers: Silicon photonics expands tunability options for communications and scientific lasers

    July 1, 2019
    Semiconductor optical amplifiers and other on- and off-chip components are being integrated in miniaturized, efficient silicon-photonics-based transceiver devices to enable broadly...
    (Courtesy of NKT Photonics)
    FIGURE 1. A schematic representation details the spectral components of scattered light within an optical fiber.
    Fiber Optics

    Fiber-optic Sensing: Smart fiber-optic sensing systems enhance physical border walls and fences

    July 1, 2019
    Distributed fiber-optic sensing architectures complement physical borders by providing accurate, cost-effective, real-time monitoring of perimeter intrusions.
    FIGURE 1. An illustration of liquid-crystal metasurface (LCM) beam steering depicts its operation. The incident light is TM-polarized. Shown here, the LCM steers to two different output angles (a and b), determined by the spatial frequency of the phase-modulation pattern applied to the array of tunable resonators on the LCM (c and d). Higher spatial frequencies steer the output beam closer to the incident beam.
    Optics

    Optics for Automotive Lidar: Metasurface beam steering enables solid-state, high-performance lidar

    July 1, 2019
    A large-aperture, large-field-of-view dynamic liquid crystal metasurface beam steerer for automotive lidar has no moving parts.
    (Courtesy of Andreas Thoss)
    Reinhart Poprawe with some of his 200 PhD students.
    Lasers & Sources

    Business Forum: An era ends—Reinhart Poprawe retires

    Andreas Thoss
    July 1, 2019
    After 23 years shaping industrial laser technology development in Germany and worldwide, Reinhart Poprawe retires from Fraunhofer ILT and RWTH Aachen University.