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  • Volume 53, Issue 10

    • Volume 53, Issue 10

    1304qa Chang New
    Lasers & Sources

    Business Forum: What to do when you see criminal behavior in a photonics business

    Milton Chang
    Oct. 14, 2017
    A murky area is: are you required to report a photonics crime as an observer? The answer is "it depends."
    (Courtesy of PI)
    FIGURE 1. Silicon photonics couplings often deviate from clean predictable Gaussian coupling cross-section. Profiles of this sort cannot be reliably optimized with traditional alignment algorithms. Otherwise, the optimization risks locking onto one of the local optima rather than the global optimum. This can be efficiently achieved by performing an areal scan of the target area, thereby mapping the coupling cross-section across its full extent. A piezo-based scanner can achieve this in fractions of a second.
    Positioning, Support & Accessories

    Positioning: Silicon photonics manufacturing requires parallelism in alignment processes

    Scott Jordan
    Oct. 13, 2017
    To make silicon photonics devices profitably at scale, automation subsystems require alignment processes that support steps from device characterization at the wafer level to ...
    Eadweard Muybridge/Library of Congress Prints and Photographs Division via Wikimedia Commons
    FIGURE 1. A series of photographs of a galloping horse at different points during its gait were taken by Eadweard Muybridge in 1878, illustrating a time-stretched event.
    Spectroscopy

    Spectroscopy: Time-stretch spectroscopy STEAMs ahead

    Oct. 13, 2017
    Stretching pulses of light in time enables serial time-encoded amplified microscopy (STEAM) and other time-stretch applications.
    (Courtesy of Alcon)
    FIGURE 1. Alcon's LenSx Laser has been used in more cataract surgeries worldwide than any other femtosecond laser, having reached one million procedures in 2017; the system automates cataract procedures and provides high-definition OCT imaging for guidance.
    Research

    Ophthalmology/Femtosecond Lasers: Clarity on the laser cataract conundrum

    Barbara Gefvert
    Oct. 13, 2017
    In less than a decade, femtosecond laser-assisted cataract surgery has gone from hotly anticipated to coolly considered. Now, developers are addressing the barriers, while the...
    Courtesy of NASA
    FIGURE 1. A NASA prototype solar sail was fabricated with a conventional metallic reflective surface; however, a diffractive solar-sail concept developed at the Rochester Institute of Technology has potential advantages that include higher efficiency and less absorption.
    Optics

    Space and Astronomy: Diffractive solar sails could outperform reflective-metal-coated sails

    Oct. 12, 2017
    Using a diffraction grating for a lightsail has advantages including a large force component perpendicular to the direction of the sun.

    More content from Volume 53, Issue 10

    (Courtesy of Philips Photonics)
    FIGURE 1. A Philips Photonics high-power VCSEL array consists of many laser apertures in hexagonal packing and surrounded by gold contacts.
    Lasers & Sources

    Vertical-cavity Surface-emitting Lasers: VCSEL arrays provide leading-edge illumination for 3D sensing

    Holger Mönch
    Oct. 12, 2017
    Vertical-cavity surface-emitting laser arrays enable power scaling for lidar and other sensing applications.
    FIGURE 1. An optical time-domain spectroscopy unit (a) generates the ultrafast pump/probe signals while the near-field scanner unit (b) includes the terahertz emitter and near-field detector components, as well as translation stages for high-resolution field mapping; a sample or device under test is loaded to the near-field scanner unit.
    Detectors & Imaging

    Photonics Applied: Terahertz Imaging: Terahertz imaging tackles solar cell and semiconductor process inspection

    Michael Nagel
    Oct. 12, 2017
    Replacing free-space optics with fiber-coupled, integrated components allows modular terahertz time-domain imaging systems to excel in solar and semiconductor wafer analysis.
    Terahertz-radiation outputs from a water film and from the air surrounding it can be separately measured. At the top is shown a situation in which the laser passes through the water film first and then focuses; here, a terahertz output characteristic of air is seen (similar to control setup at bottom of figure with no water film). Next, when the focus is moved to within the water film itself, the desired terahertz output from the water is seen. Finally, when the laser focuses first and then passes through the water, no terahertz output is seen because of absorption of terahertz radiation in the water.
    Lasers & Sources

    Terahertz Sources: Femtosecond laser pulses produce ultrafast terahertz radiation from water

    John Wallace
    Oct. 12, 2017
    While terahertz radiation has been generated from solids, gases, and plasmas (the "fourth state" of matter) before, no one had created terahertz light from a liquid—until now....
    (Courtesy of Mark Montagut/ICFO)
    An illustration (a) shows CVD graphene transferred onto a single CMOS die (15.1 × 14.3 mm) with standard ROIC components in a 388 × 288 pixel array. The side view (b) shows the graphene layer and application of lead-sulfide (PbS) quantum dots and (c) their pixel architecture. On QD light absorption, an electron-hole pair is generated, the hole transfers to the graphene, and the electron is trapped in the QD; per the schematic (d), the balanced readout scheme is detailed into typical CMOS functional areas with a particular pixel pattern (e), as shown in the expanded areas (before QD application for clarity).
    Detectors & Imaging

    CMOS Sensors: Graphene and quantum dots combine for broadband CMOS camera

    Gail Overton
    Oct. 12, 2017
    A collaboration has integrated graphene with quantum-dot photodetectors on a CMOS platform to create a broadband imaging sensor.
    Experimental and simulated propagation losses of a mid-IR integrated multimode-interference (MMI) Mach-Zehnder interferometer are plotted for both TE (a) and TM (b) polarizations; the horizontal lines at -1.0 dB in both charts are just reference eye guides.
    Optics

    Photonic Integrated Circuits: Wideband integrated mid-IR Mach-Zehnder interferometer looks good for spectroscopy

    John Wallace
    Oct. 12, 2017
    Researchers have broken the 1-micron bandwidth barrier by creating an integrated mid-IR waveguide Mach-Zehnder interferometer that has a 3-micron spectral operating range.
    In a demonstration of the on-off switch effect of collimated polarized light imaging (CPLi), the blue arrow highlights a vertical structure (a), which appears whiter after rotating the polarizers (b). The opposite occurs at the oblique structure (green arrow) indicating nerve tissue. The CPLi stereo microscope that produced these images features a pair of adjustable collimation lenses that refract the light of 3 W LEDs on either side of the unit. It also provides a linear polarizer (on the outer rim of a polarization disk) that aligns perpendicularly to an inner linear polarizer.
    Research

    Tissue Imaging: Got nerve? Collimated polarized light can tell

    Barbara Gefvert
    Oct. 12, 2017
    But polarized light is showing the way to real-time, noninvasive visualization of nerve tissue.
    (Courtesy of AdlOptica)
    Multifocus optics produce many different focal points-four (a) and seven (b) shown here—and can be manually adjusted to deliver a desired materials processing effect such as a more longitudinal, uniform beam profile by distributing the energy from four focal spots (c) as compared to a single focus (d).
    Optics

    Optics for Materials Processing: Multifocus optics target materials processing, but hint at novel uses

    Gail Overton
    Oct. 12, 2017
    Whether cutting, welding, or patterning various materials using a laser, the materials-processing end result correlates directly with the size, shape, and intensity of the laser...
    Content Dam Lfw Print Articles 2017 10 1710lfw Nb F3
    Optics

    Spatiotemporally modulated optical mirror reflects in one direction, transmits in the other

    John Wallace
    Oct. 12, 2017
    Researchers have come up with a way to create a bulk nonreciprocal mirror that, at least in theory, can have a 50 dB isolation and a very high reflection.
    Content Dam Lfw Print Articles 2017 10 1710lfw Nb F4
    Detectors & Imaging

    Plasmonic photoswitch sensor consumes no power unless IR signal is present

    Gail Overton
    Oct. 12, 2017
    An infrared sensor based on a plasmonically enhanced micromechanical photoswitch remains dormant with near-zero power consumption until awakened by an external trigger or stimulus...
    Content Dam Lfw Print Articles 2017 10 1710lfw Nb F2
    Research

    Opto-thermophoretic method easily assembles colloidal matter

    Gail Overton
    Oct. 12, 2017
    An optothermophoretic assembly method uses an ionic surfactant to manipulate and assemble most any colloidal matter using a light-controlled temperature field.
    Content Dam Lfw Print Articles 2017 10 1710lfw Nb F1
    Research

    Ultrashort light pulse speed in vacuum can be controlled, simulation says

    John Wallace
    Oct. 12, 2017
    Physicists have theoretically determined that ultrafast laser pulses can, when focused, be made to travel at different velocities when propagating in a vacuum.
    Conard Holton2
    Lasers & Sources

    The photonics 'wow' factor

    Conard Holton
    Oct. 12, 2017
    The great thing about both the business and technology sides of photonics is that you get a lot of "wows."