• New self-cleaning optical fiber can help

    From ScienceDaily@1:317/3 to All on Friday, April 22, 2022 22:30:48
    New self-cleaning optical fiber can help in monitoring environment and diagnosing cancer

    Date:
    April 22, 2022
    Source:
    Tampere University
    Summary:
    Researchers have successfully developed a novel optical fiber design
    allowing the generation of rainbow laser light in the molecular
    fingerprint electromagnetic region. This new optical fiber with
    a self- cleaned beam can help in developing applications to, for
    example, tagging pollutants, cancer diagnostics, environmental
    monitoring, and food control.



    FULL STORY ========================================================================== Researchers at Tampere University have successfully developed a novel
    optical fiber design allowing the generation of rainbow laser light in the molecular fingerprint electromagnetic region. This new optical fiber with
    a self-cleaned beam can help in developing applications to, for example, tagging pollutants, cancer diagnostics, environmental monitoring, and food control. The finding was published in the journal Nature Communications.


    ==========================================================================
    When a high-power ultrashort pulse of light interacts with a material
    such as a glass optical fibre, a range of highly nonlinear interactions
    take place that cause complex changes in both the temporal and spectral properties of the injected light. When taken to the extreme, such
    interactions can lead to the generation of a rainbow laser of light
    commonly referred to as a supercontinuum light source. Since its first demonstration in a special type of optical fiber in 2000, supercontinuum
    laser light has revolutionized many areas of science, ranging from
    metrology and imaging at unprecedented resolution to ultrabroadband
    remote sensing and even the detection of exoplanets.

    The current bottleneck with current supercontinuum sources, however, is
    that they are based on optical fibers that support a single transverse intensity profile or mode, which inherently limits their optical
    power. What's more, conventional optical fibers are made of silica
    glass with transmission limited to the visible and near-infrared region
    of the spectrum. Extension of supercontinuum light to other wavelength
    regimes such the mid-infrared requires optical fibers made of so-called
    soft glasses, but these possess a lower damage threshold than silica,
    limiting even more the power of the supercontinuum beam.

    Non-silica optical fiber with a self-cleaned beam Recently, a different
    type of optical fiber with a refractive index that varies continuously
    across the fiber structure has been shown to yield a dramatic increase
    in supercontinuum power, while still preserving a smooth beam intensity profile. "The refractive index variation of such graded-index optical
    fibers leads to periodic focusing and defocusing of the light inside
    the fiber that enables coupling between spatial and temporal nonlinear light-matter interactions. This leads to a self-cleaning mechanism that
    yields supercontinuum light with high power and a clean beam profile. As
    well as their many applications, they also provide a means of studying fundamental physics effects such as wave turbulence," says Professor
    Goe"ry Genty, the leader of the research group at Tampere University.

    While these fibers have recently attracted significant attention from
    the research community, their use has been, up to now, restricted
    to the visible and near-infrared. In collaboration with the group of
    Profs. Buczynski and Klimczak at the University of Warsaw (Poland) and
    the group of Prof. Dudley in the University of Burgundy France-Comte'
    (France), the Tampere team demonstrated for the first time the generation
    of a two-octave supercontinuum from the visible to mid-infrared in a
    non-silica graded-index fiber with a self-cleaned beam.

    "This problem has now been solved by using a particular design that
    utilizes two types of lead-bismuth-gallate glass rods with different
    refractive indices drawn to yield a nanostructured core. The result is a graded-index fiber with an effective parabolic refractive index profile
    with transmission up to the mid-infrared, and, as cherry on the cake,
    enhanced nonlinear light-matter interactions," says researcher Zahra
    Eslami.

    Great potential in diagnostics and monitoring The mid-infrared is of
    crucial interest as it contains the characteristic vibrational transitions
    of many important molecules.

    "The novel solution will lead to more efficient supercontinuum light
    sources in the mid-infrared with many potential applications e.g., for pollutant tagging, cancer diagnostics, machine vision, environmental monitoring, quality and food control," explains Genty.

    The researchers anticipate that this novel type of fiber will very soon
    become an important and standard material for the generation of broadband sources and frequency combs.

    The research was carried out at Tampere University and within the Academy
    of Finland Flagship for Photonics Research and Innovation (PREIN).


    ========================================================================== Story Source: Materials provided by Tampere_University. Note: Content
    may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Zahra Eslami, Lauri Salmela, Adam Filipkowski, Dariusz Pysz, Mariusz
    Klimczak, Ryszard Buczynski, John M. Dudley, Goe"ry Genty. Two
    octave supercontinuum generation in a non-silica graded-index
    multimode fiber.

    Nature Communications, 2022; 13 (1) DOI: 10.1038/s41467-022-29776-6 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/04/220422094318.htm

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