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    • Volume 55, Issue 07

    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.
    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...
    July 1, 2019
    1907 Lfw09 12 Nb 4
    A nitrogen-vacancy (NV) diamond produces single photons; a metalens etched into its surface collects them, no microscope needed.
    July 1, 2019
    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.
    Approaches for determining laser beam quality differ for different applications; this summary of best practices covers them all.
    July 1, 2019
    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).
    Nanowires of InAs and InAsSb on an indium phosphide substrate form room-temperature SWIR or MWIR photodiodes suitable for focal-plane arrays.
    July 1, 2019
    1907 Lfw09 12 Nb 3
    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...
    July 1, 2019
    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.
    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...
    July 1, 2019
    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.
    A rotatable lithium niobate upconversion crystal generates phase matching of concentric rings in the object plane, leading to a wide field of view.
    July 1, 2019
    1907 Lfw Nb F1
    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...
    July 1, 2019
    (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.
    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...
    July 1, 2019
    (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.
    Narrowline blue laser emission has been reported from an electrically pumped film of the organic substance BSBCz coupled with a distributed-feedback grating.
    July 1, 2019
    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).
    Semiconductor optical amplifiers and other on- and off-chip components are being integrated in miniaturized, efficient silicon-photonics-based transceiver devices to enable broadly...
    July 1, 2019
    (Courtesy of NKT Photonics)
    FIGURE 1. A schematic representation details the spectral components of scattered light within an optical fiber.
    Distributed fiber-optic sensing architectures complement physical borders by providing accurate, cost-effective, real-time monitoring of perimeter intrusions.
    July 1, 2019
    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.
    A large-aperture, large-field-of-view dynamic liquid crystal metasurface beam steerer for automotive lidar has no moving parts.
    July 1, 2019
    (Courtesy of Andreas Thoss)
    Reinhart Poprawe with some of his 200 PhD students.
    After 23 years shaping industrial laser technology development in Germany and worldwide, Reinhart Poprawe retires from Fraunhofer ILT and RWTH Aachen University.
    July 1, 2019