Ultra-short flashes of light combined precisely and quickly

Only separated by quadrillionths of a second: Ultra-short flashes of light combined precisely and quickly

Ultra-short solitons overlay and produce spectral interference patterns: Real-time spectroscopy resolves their rapid dynamics and tracks the switching of soliton molecules in a femtosecond fiber laser. The image shows successive experimental spectra recorded during a switching process. Credit: Moritz B. Heindl

Ultra-short flashes of light lasting less than a quadrillionth of a second are growing rapidly in technological terms. In laser sources, pairs and groups of flashes of light can be created instead of individual flashes. Like the chemically bound atoms in a molecule, they are linked together and their short time intervals can have remarkable stability. Researchers at the universities of Bayreuth and Constance have now revealed a reason for the stable coupling of ultra-short flashes of light and found a way to control their distance both very accurately and quickly. They present their research results in the journal OPTICAL.

Flashes of light shorter than a quadrillionth of a second are also called femtosecond pulses. Today, they are used for research into energy materials, for 3D manufacturing of components or as precision scalps in medicine. In lasers, these flashes are created as solitons, stable packets of light waves. The results of their coupling, which have now been published, were obtained on a laser resonator. This contains a ring of fiberglass that allows the solitons to circulate indefinitely. In such systems, coupled femtosecond flashes, so-called soliton molecules, are often observed. Using high-resolution real-time spectroscopy, the research team was able to track the dynamics of two coupled flashes in real time over many hundreds of thousands of circuits. Based on these data, the researchers were able to show that it is optical reflections in the laser resonator that couple the individual solitons in time and space. The bonding distances could be predicted on the basis of transit time differences in the resonator and could finally be precisely adjusted by changing optical elements.

In addition, the new study shows how the bond between two flashes can be quickly loosened and a new bond created. For example, it is now possible to specifically switch back and forth between flashes of light that occur in pairs and have different time intervals. “Based on our research results, it is now possible to switch soliton molecules at the touch of a button. This opens up new perspectives for the technical application of femtosecond pulses, especially in spectroscopy and material processing,” says Luca Nimmesgern B.Sc. , first author of the study and physics graduate student at the University of Bayreuth.

The results obtained by the laser resonator can be transmitted to a variety of ultra-short pulse laser sources. As a result, it is possible to generate coupled flashes of light in other laser systems and change their distances without much effort. “Since the first reports of pulse pairs in fiber lasers more than 20 years ago, various explanations for the stability of soliton molecules in lasers have been proposed. The usual models have been contradicted by several observations, but are still used today. Our new study now offers an accurate explanation that is compatible with the measured data for the first time.In a way, it provides a piece in the puzzle that makes a wide range of previous data understandable.Now complex laser physics can be used specifically to generate soliton sequences by high speed, “says Georg Herink, junior professor of ultra-fast dynamics at the University of Bayreuth and coordinator of research work. Co-author Prof. Dr. Alfred Leitenstorfer of the University of Konstanz, whose research team has been developing fiber lasers as a tool for spectroscopy for years, adds: “Based on our new results, we can look forward to the realization of versatile technological applications.”

At the University of Bayreuth, a DFG research project was recently launched with the aim of understanding the interactions between ultra-short solitons in laser sources in detail and making them useful for future laser applications.


Always on beat: Ultra-short flashes of light under optical control


More information:
Luca Nimmesgern et al., Soliton molecules in femtosecond fiber lasers: universal binding mechanism and direct electronic control, OPTICAL (2021). DOI: 10.1364 / OPTICA.439905

Provided by the University of Bayreuth

Citation: Only separated by quadrillionths of a second: Ultra-short flashes of light combined precisely and quickly (2021, November 1) Retrieved November 2, 2021 from https://phys.org/news/2021-11-quadrillionths-ultrashort-combined-precisely- fast.html

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