To solve this problem, a French-English collaboration (2) led by Raffaele Colombelli, researcher at CNRS, has used special microscopic components called photonic crystals. In combination with the laser, the team was able to control the laser beam and considerably restrict its divergence. Published on January 8 in the journal Nature, this finding opens the way to a large number of promising applications, for instance in the field of terahertz medical imaging.
Situated in the far infrared range of the electromagnetic spectrum, between mid-infrared and microwaves, terahertz waves have some major advantages: they can penetrate through skin, clothing, paper, wood, card and plastic. These properties offer applications in medical imaging, spectroscopy, and environmental detection (detection of biological agents, pollutants etc.). .
Terahertz cascade laser systems raise considerable interest due to their numerous advantages: they are compact (3), they use electrical energy -- reference is made to electrically "pumped" lasers (4) - and they operate in the terahertz range of the electromagnetic spectrum (THz). Indeed, the generation of radiation in the frequency range between 1 and 10 THz (also called the THz "gap") with a compact device has proven extremely challenging. This explains the considerable interest raised by terahertz cascade lasers, which are the only compact sources (smaller than a millimeter) operating within this range of frequencies. However, these promising lasers have one weakness: the marked divergence of their output beam, which prevents their widespread use.
The scientists used very small structures, photonic crystals, to influence the optical properties of the material and thus enable control over the light trajectory. By combining these components with the terahertz laser, they managed to design an ingenious system that emits terahertz waves but also, and above all, enables precise control of the laser beam. Thanks to this effective technology, this beam now diverges very little.
This novel system opens up numerous fundamental and applied perspectives. It is now necessary for the researchers to maximize the output power of these lasers. Furthermore, better control of the photonic crystal technology may enable the design of new terahertz lasers of an even smaller size. The technique thus developed could be generalized to other lasers operating in different ranges of wavelengths. Finally, these results may give rise to several applications, notably in the fields of spectroscopy and THz imaging.
This work was made possible by the EURYI award given in 2004 to Raffaele Colombelli by the European Science Foundation. This allowed him to set up a research team within the Institut d'électronique fondamentale at the Faculty of Sciences in Orsay, where he is supervising the doctoral thesis of Yannick Chassagneux, the lead author of this publication.
(1) The first terahertz quantum cascade laser was invented in 2002.(2) Belonging to two units: the Institut d'électronique fondamentale
Julien Guillaume | alfa
Magnetic nano-imaging on a table top
20.04.2018 | Georg-August-Universität Göttingen
New record on squeezing light to one atom: Atomic Lego guides light below one nanometer
20.04.2018 | ICFO-The Institute of Photonic Sciences
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
20.04.2018 | Physics and Astronomy
20.04.2018 | Interdisciplinary Research
20.04.2018 | Physics and Astronomy