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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