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News Article | November 10, 2016
Site: www.eurekalert.org

Working with physicists from the University of Rome, a team led by Professor Cordt Zollfrank from the Technical University of Munich (TUM) built the first controllable random laser based on cellulose paper in Straubing. The team thereby showed how naturally occurring structures can be adapted for technical applications. Hence, materials no longer need to be artificially outfitted with disordered structures, utilizing naturally occurring ones instead. Material synthesis that is inspired by biology is an area of research at TUM's Chair of Biogenic Polymers at the Straubing Center of Science. It utilizes models from nature and biogenic materials to develop new materials and technologies. The latest issue of the publication "Advanced Optical Materials" features a basic study by a joint team from Straubing and Rome who succeeded in "using a biological structure as a template for a technical random laser," according to scientist Dr Daniel Van Opdenbosch. Two components are necessary for a laser: First of all, a medium which amplifies light. And secondly, a structure which retains the light in the medium. A classic laser uses mirrors to order and shine light in a single direction in a targeted, uniform fashion. This also takes place uniformly in the microscopic structure of a random laser, but in different directions. Although the development of the random laser is still in its infancy, in the future it could result in lower-cost production. This is because random lasers have the advantage that they are direction-independent and function with multiple colors, just to name a few benefits. "The prerequisite for a random laser is a defined degree of structural chaos on the interior," Van Opdenbosch explained. The light in a random laser is therefore scattered at all manner of angles along random paths, which are determined by an irregular structure in the interior of the medium. The team led by Professor Zollfrank from the Chair of Biogenic Polymers in Straubing used conventional laboratory filter paper as a structural template. "Due to its long fibers and the resulting stable structure, we deemed it to be suitable for this purpose," said Van Opdenbosch. In the laboratory, the paper was impregnated with tetraethyl orthotitanate, an organometallic compound. When it is dried and the cellulose burned off at 500 degrees Celsius, it leaves behind the ceramic titanium dioxide as residue -- the same substance generally used in sunblock to provide protection from the sun. "This effect in sunblock is based on titanium dioxide's strong light scattering effect," said Van Opdenbosch, "which we also utilized for our random laser." And "our laser is 'random' because the light which is scattered in different directions due to the biogenic structure of the laboratory filter paper can also be scattered in the opposite direction," he added, explaining the principle. Random laser not that random after all However, the light waves can still be controlled despite their random nature, as the team led by Claudio Conti of the Institute for Complex Systems in Rome discovered, with whom Daniel Van Opdenbosch and Cordt Zollfrank collaborated. With the help of a spectrometer, they were able to differentiate the various laser wavelengths generated in the material and localize them separately from one another. Van Opdenbosch described the procedure: "The test setup used to map the samples consisted of a green laser whose energy could be adjusted, microscope lenses, and a mobile table which allowed the sample to be moved past. That way, our colleagues were able to determine that at different energy levels, different areas of the material radiate different laser waves." In light of this analysis, it is possible to configure the laser in any number of ways and to determine the direction and intensity of its radiation. This knowledge puts potential practical applications within reach. "Such materials could, for example, be useful as micro-switches or detectors for structural changes," said Van Opdenbosch. Ghofraniha, Neda, Luca La Volpe, Daniel Van Opdenbosch, Cordt Zollfrank, and Claudio Conti: Biomimetic Random Lasers with Tunable Spatial and Temporal Coherence, Advanced Optical Materials, September 2016. doi:10.1002/adom.201600649.


News Article | November 10, 2016
Site: www.sciencedaily.com

Working with physicists from the University of Rome, a team led by Professor Cordt Zollfrank from the Technical University of Munich (TUM) built the first controllable random laser based on cellulose paper in Straubing. The team thereby showed how naturally occurring structures can be adapted for technical applications. Hence, materials no longer need to be artificially outfitted with disordered structures, utilizing naturally occurring ones instead. Material synthesis that is inspired by biology is an area of research at TUM's Chair of Biogenic Polymers at the Straubing Center of Science. It utilizes models from nature and biogenic materials to develop new materials and technologies. The latest issue of the publication "Advanced Optical Materials" features a basic study by a joint team from Straubing and Rome who succeeded in "using a biological structure as a template for a technical random laser," according to scientist Dr Daniel Van Opdenbosch. Two components are necessary for a laser: First of all, a medium which amplifies light. And secondly, a structure which retains the light in the medium. A classic laser uses mirrors to order and shine light in a single direction in a targeted, uniform fashion. This also takes place uniformly in the microscopic structure of a random laser, but in different directions. Although the development of the random laser is still in its infancy, in the future it could result in lower-cost production. This is because random lasers have the advantage that they are direction-independent and function with multiple colors, just to name a few benefits. "The prerequisite for a random laser is a defined degree of structural chaos on the interior," Van Opdenbosch explained. The light in a random laser is therefore scattered at all manner of angles along random paths, which are determined by an irregular structure in the interior of the medium. The team led by Professor Zollfrank from the Chair of Biogenic Polymers in Straubing used conventional laboratory filter paper as a structural template. "Due to its long fibers and the resulting stable structure, we deemed it to be suitable for this purpose," said Van Opdenbosch. In the laboratory, the paper was impregnated with tetraethyl orthotitanate, an organometallic compound. When it is dried and the cellulose burned off at 500 degrees Celsius, it leaves behind the ceramic titanium dioxide as residue -- the same substance generally used in sunblock to provide protection from the sun. "This effect in sunblock is based on titanium dioxide's strong light scattering effect," said Van Opdenbosch, "which we also utilized for our random laser." And "our laser is 'random' because the light which is scattered in different directions due to the biogenic structure of the laboratory filter paper can also be scattered in the opposite direction," he added, explaining the principle. Random laser not that random after all However, the light waves can still be controlled despite their random nature, as the team led by Claudio Conti of the Institute for Complex Systems in Rome discovered, with whom Daniel Van Opdenbosch and Cordt Zollfrank collaborated. With the help of a spectrometer, they were able to differentiate the various laser wavelengths generated in the material and localize them separately from one another. Van Opdenbosch described the procedure: "The test setup used to map the samples consisted of a green laser whose energy could be adjusted, microscope lenses, and a mobile table which allowed the sample to be moved past. That way, our colleagues were able to determine that at different energy levels, different areas of the material radiate different laser waves." In light of this analysis, it is possible to configure the laser in any number of ways and to determine the direction and intensity of its radiation. This knowledge puts potential practical applications within reach. "Such materials could, for example, be useful as micro-switches or detectors for structural changes," said Van Opdenbosch.


Mulansky M.,CNR Institute of Neuroscience | Bozanic N.,CNR Institute of Neuroscience | Sburlea A.,Institute for Complex Systems | Sburlea A.,University of Zaragoza | Kreuz T.,CNR Institute of Neuroscience
Proceedings of 1st International Conference on Event-Based Control, Communication and Signal Processing, EBCCSP 2015 | Year: 2015

Measures of spike train synchrony have proven a valuable tool in both experimental and computational neuroscience. Particularly useful are time-resolved methods such as the ISI-and the SPIKE-distance, which have already been applied in various bivariate and multivariate contexts. Recently, SPIKE-Synchronization was proposed as another time-resolved synchronization measure. It is based on Event-Synchronization and has a very intuitive interpretation. Here, we present a detailed analysis of the mathematical properties of these three synchronization measures. For example, we were able to obtain analytic expressions for the expectation values of the ISI-distance and SPIKE-Synchronization for Poisson spike trains. For the SPIKE-distance we present an empirical formula deduced from numerical evaluations. These expectation values are crucial for interpreting the synchronization of spike trains measured in experiments or numerical simulations, as they represent the point of reference for fully randomized spike trains. © 2015 IEEE.


News Article | November 10, 2016
Site: phys.org

Material synthesis that is inspired by biology is an area of research at TUM's Chair of Biogenic Polymers at the Straubing Center of Science. It utilizes models from nature and biogenic materials to develop new materials and technologies. The latest issue of the publication Advanced Optical Materials features a basic study by a joint team from Straubing and Rome who succeeded in "using a biological structure as a template for a technical random laser," according to scientist Dr Daniel Van Opdenbosch. Two components are necessary for a laser: First of all, a medium which amplifies light. And secondly, a structure which retains the light in the medium. A classic laser uses mirrors to order and shine light in a single direction in a targeted, uniform fashion. This also takes place uniformly in the microscopic structure of a random laser, but in different directions. Although the development of the random laser is still in its infancy, in the future it could result in lower-cost production. This is because random lasers have the advantage that they are direction-independent and function with multiple colors, just to name a few benefits. "The prerequisite for a random laser is a defined degree of structural chaos on the interior," Van Opdenbosch explained. The light in a random laser is therefore scattered at all manner of angles along random paths, which are determined by an irregular structure in the interior of the medium. The team led by Professor Zollfrank from the Chair of Biogenic Polymers in Straubing used conventional laboratory filter paper as a structural template. "Due to its long fibers and the resulting stable structure, we deemed it to be suitable for this purpose," said Van Opdenbosch. In the laboratory, the paper was impregnated with tetraethyl orthotitanate, an organometallic compound. When it is dried and the cellulose burned off at 500 degrees Celsius, it leaves behind the ceramic titanium dioxide as residue—the same substance generally used in sunblock to provide protection from the sun. "This effect in sunblock is based on titanium dioxide's strong light scattering effect," said Van Opdenbosch, "which we also utilized for our random laser." And "our laser is 'random' because the light which is scattered in different directions due to the biogenic structure of the laboratory filter paper can also be scattered in the opposite direction," he added, explaining the principle. Random laser not that random after all However, the light waves can still be controlled despite their random nature, as the team led by Claudio Conti of the Institute for Complex Systems in Rome discovered, with whom Daniel Van Opdenbosch and Cordt Zollfrank collaborated. With the help of a spectrometer, they were able to differentiate the various laser wavelengths generated in the material and localize them separately from one another. Van Opdenbosch described the procedure: "The test setup used to map the samples consisted of a green laser whose energy could be adjusted, microscope lenses, and a mobile table which allowed the sample to be moved past. That way, our colleagues were able to determine that at different energy levels, different areas of the material radiate different laser waves." In light of this analysis, it is possible to configure the laser in any number of ways and to determine the direction and intensity of its radiation. This knowledge puts potential practical applications within reach. "Such materials could, for example, be useful as micro-switches or detectors for structural changes," said Van Opdenbosch. Explore further: Focused light in the Terahertz regime consisting of a broad spectrum of wavelengths More information: Neda Ghofraniha et al, Biomimetic Random Lasers with Tunable Spatial and Temporal Coherence, Advanced Optical Materials (2016). DOI: 10.1002/adom.201600649


PubMed | University of Rome La Sapienza and Institute for Complex Systems
Type: | Journal: Scientific reports | Year: 2015

More than thirty years ago Glauber suggested that the link between the reversible microscopic and the irreversible macroscopic world can be formulated in physical terms through an inverted harmonic oscillator describing quantum amplifiers. Further theoretical studies have shown that the paradigm for irreversibility is indeed the reversed harmonic oscillator. As outlined by Glauber, providing experimental evidence of these idealized physical systems could open the way to a variety of fundamental studies, for example to simulate irreversible quantum dynamics and explain the arrow of time. However, supporting experimental evidence of reversed quantized oscillators is lacking. We report the direct observation of exploding n=0 and n=2 discrete states and 0 and 2 quantized decay rates of a reversed harmonic oscillator generated by an optical photothermal nonlinearity. Our results give experimental validation to the main prediction of irreversible quantum mechanics, that is, the existence of states with quantized decay rates. Our results also provide a novel perspective to optical shock-waves, potentially useful for applications as lasers, optical amplifiers, white-light and X-ray generation.

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