An international team of physicists from the University of Kassel, led by Prof. Thomas Baumert, and the University of Aarhus, led by Prof. Peter Balling, discovered that ultra-short laser pulses are amplified in a laser excited piece of glass. This amplification, similar to a classical laser, is directed and of coherent nature. By utilizing theoretical models and simulations, the researchers were able to understand and reproduce the multi-step process leading to the “Laser Amplification in Excited Dielectrics” (short: LADIE) named effect. Their results were published online in the well-known research journal Nature Physics.
If a transparent dielectric material like water or glass is illuminated by visible or infrared light it is transmitted without loss. This quickly changes if ultra-short laser pulses on the femtosecond timescale (quadrillionth second) are used:
Caused by the high intensities that such laser pulses provide, different interaction mechanisms are able to transfer the transparent material into a metallic like state. The created “free” electrons, similar to a metal, play a significant role in the change of the optical properties associated to the excitation of the material.
Accordingly, pump-probe experiments, utilizing two temporally delayed laser pulses were proven to be a very useful method to investigate the laser-material interaction. Indeed, most experiments show that shortly after the laser excitation, absorption and reflection increase due to the creation of high density of free electrons giving the dielectric material transient metallic properties.
Researchers from the Experimental Physics III located at the University of Kassel, in cooperation with colleagues from the Department of Physics at the University of Aarhus in Denmark, recently performed similar experiments on laser excited sapphire glass.
Much to their surprise, the researchers observed that the absorption of a violet probe pulse is, under certain conditions, replaced by coherent amplification. The physicists could link the observed amplification to the, so far, unobserved LADIE mechanism. While in typical light amplification processes, such as a laser, single photons are doubled, the study suggests that the LADIE process provides a multi photon process, for example making four out of two incident photons.
“It is too early to foresee possible impacts or applications of the LADIE effect”, says Thomas Winkler, scientist at the Kassel Department of Physics. “Yet it provides a more detailed understanding of the light material interaction. However, also the discovery of the LASER in the mid 60s by Theodore Maiman was an unusual discovery that was initially seen as no more than another thrilling aspect of quantum physics. However, today, more than 50 years later, there are no products or technical process in which laser-technology is not involved in a certain way.”
The publication was published on Monday, 18th September 2017 and is available under the following link: https://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys4265.html
For a picture (copyright: Uni Kassel), please see: https://www.uni-kassel.de/uni/fileadmin/datas/uni/presse/anhaenge/2017/NatPhysic...
Institut für Physik
Tel.: +49 561 804 4319
Prof. Dr. Thomas Baumert
Institut für Physik
Tel: +49 561 804 4452
Sebastian Mense | idw - Informationsdienst Wissenschaft
Highest-energy cosmic rays have extragalactic origin
25.09.2017 | CNRS
NASA'S OSIRIS-REx spacecraft slingshots past Earth
25.09.2017 | NASA/Goddard Space Flight Center
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
25.09.2017 | Physics and Astronomy
25.09.2017 | Trade Fair News
25.09.2017 | Physics and Astronomy