Self-cleaning optical fibres can be helpful in diagnosing and monitoring the environment.

Tampere University researchers have created a new optical fiber design that generates rainbow laser light in the region of the molecular fingerprint electromagnetic. This new optical fiber can be used to develop applications for environmental monitoring, food control, cancer diagnostics and pollutant tagging. The journal published the results. Nature Communications.

High-powered, ultrashort pulses of light interact with a material such a glass optical fiber to produce complex changes in the spectral and temporal properties. These interactions can result in the creation of a rainbow-colored laser of light, commonly known as a supercontinuum source of light. Supercontinuum light has revolutionized many science areas, from metrology and imaging with unprecedented resolution to ultrabroadband remote sense and even the detection and detection of exoplanets, since its first demonstration in 2000 in a special optical fibre.

The current issue with supercontinuum sources is that they are based only on optical fibers which support a single transverse intensity profile or mode. This limits their optical power. Additionally, optical fibers made of conventional silica glass have transmission limits that limit them to the visible and near infrared regions of the spectrum. Soft glasses are optical fibers that extend supercontinuum light to other wavelengths, such as the mid infrared. These have a lower damage threshold than silicona, which limits the supercontinuum beam’s power.

Non-silica optical fibre with a self-cleaned beam

A new type of optical fiber that has a constant refractive index across the fiber structure was recently shown to have a dramatic increase in supercontinuum powers while maintaining a smooth beam intensity profile. “The graded-index refractive variation of such optical fibers results in periodic focusing and defocusing the light inside the fiber, which enables coupling between spatial- and temporal nonlinear light–matter interactions. This results in a self-cleaning mechanism which produces supercontinuum light with high power, and a clean beam profile. They are useful for many purposes and also allow us to study fundamental physics effects like wave turbulence,” says Professor Gory Genty of Tampere University.

These fibers have been receiving a lot of attention in the recent research community. However, their use has remained limited to the near-infrared and visible. The group of Profs. Buczynski, Klimczak (Poland), and Prof. Dudley (France), the Tampere group demonstrated for the first-time the generation of a supercontinuum in visible to mid-infrared using a non-silica-index fiber and a beam with a self-cleaning beam.

“This problem was solved by using a specific design that uses two types of lead-bismuth–gallate glass rods with different indices drawn to produce a nanostructured center. Researchers Zahra and Eslami describe the results as a graded-index fiber that has a parabolic refractive indice profile, transmission up to mid-infrared, as well enhanced nonlinear light matter interactions.

There is great potential in monitoring and diagnostics

The mid-infrared contains important vibrational transitions for many important molecules.

Genty explains that the new solution will result in more efficient supercontinuum lights sources in mid-infrared, with many potential uses e.g. for pollutant detection, machine vision, environmental monitoring and quality control, as well as for cancer diagnostics, machine visuals, and machine vision.

The researchers predict that this type of fiber could very soon become a standard material in the generation of frequency combs and broadband source.

Provided by
Tampere University