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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