• Atomic terahertz-vibrations solve the en

    From ScienceDaily@1:317/3 to All on Fri Apr 22 22:30:48 2022
    Atomic terahertz-vibrations solve the enigma of ultrashort soliton
    molecules

    Date:
    April 22, 2022
    Source:
    Universita"t Bayreuth
    Summary:
    Optical solitons often combine into pairs with very short temporal
    separation. Introducing atomic vibrations in the terahertz range,
    researchers have solved the puzzle of how these temporal links
    are formed.



    FULL STORY ========================================================================== Stable packets of light waves -- called optical solitons -- are emitted
    in ultrashort-pulse lasers as a chain of light flashes. These solitons
    often combine into pairs with very short temporal separation. Introducing atomic vibrations in the terahertz range, researchers at the Universities
    of Bayreuth and Wrocław have now solved the puzzle of how these
    temporal links are formed. They report on their discovery in Nature Communications. The dynamics of the coupled light packets can be used to measure atomic vibrations as characteristic "fingerprints" of materials
    in an extremely fast manner.


    ==========================================================================
    In ultrashort-pulse lasers, optical solitons can form particularly tight spatial and temporal bonds. These are also called ultrashort "soliton molecules" because they are stably coupled to each other, similar to the chemically bonded atoms of a molecule. The research group in Bayreuth
    used a widely used solid-state laser made of a sapphire crystal doped
    with titanium atoms to find out how this coupling occurs. First, a single leading flash of light stimulates the atoms in the sapphire's crystal
    lattice to instantly vibrate. These characteristic motion oscillates
    in the terahertz range and decays again within a few picoseconds (a
    picosecond corresponds to a trillionth of a second). In this extremely
    short time span, the refractive index of the crystal changes. When a
    second flash of light immediately follows and catches up with the first,
    it senses this change: it is not only slightly affected by the atomic vibrations, but can also stably be bound to the preceding soliton. A
    "soliton molecule" is born.

    "The mechanism we discovered is based on the physical effects of Raman scattering and self-focusing. It explains a variety of phenomena that have puzzled science since the invention of titanium-sapphire lasers over 30
    years ago. What is particularly exciting about the discovery is that we
    can now exploit the dynamics of solitons during their generation in the
    laser cavity to scan atomic bonds in materials extremely rapidly. The
    entire measurement of a so-called intracavity Raman spectrum now takes
    less than a thousandth of a second. These findings may help to develop particularly fast chemically sensitive microscopes that can be used to
    identify materials. In addition, the coupling mechanism opens up new
    strategies to control light pulses by atomic motions and, conversely,
    to generate unique material states by light pulses," explains junior
    professor Dr. Georg Herink, head of the study and junior professor of
    ultrafast dynamics at the University of Bayreuth.

    In parallel with the analysis of experimental data, the researchers have succeeded in developing a theoretical model for soliton dynamics. The
    model allows to explain the observations obtained in experiments
    and to predict novel effects of atomic vibrations on the dynamics of
    solitons. The interactions of solitons in optical systems and their applications for high-speed spectroscopy are currently being investigated
    in the DFG research project FINTEC at the University of Bayreuth.


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


    ========================================================================== Journal Reference:
    1. Alexandra Vo"lkel, Luca Nimmesgern, Adam Mielnik-Pyszczorski,
    Timo Wirth,
    Georg Herink. Intracavity Raman scattering couples soliton molecules
    with terahertz phonons. Nature Communications, 2022; 13 (1) DOI:
    10.1038/ s41467-022-29649-y ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/04/220422094304.htm

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