Researchers developing next generation of high-power lasers

 

Fri, 08/21/2015 - 4:00pm University.of Strathclyde   Researchers at the Univ. of Strathclyde are developing groundbreaking plasma based light amplifiers that could replace traditional high-power laser amplifiers. The research group at the Glasgow-based university are leading efforts to take advantage of plasma, the ubiquitous medium that makes up most of the universe, to make the significant scientific breakthrough. The next generation of high-power lasers should be able to crack the vacuum to produce real particles from the sea of virtual particles. Example of these types of lasers can be found at the Extreme Light Infrastructure in Bucharest, Prague and Szeged, which are pushing the boundaries of what can be done with high intensity light. Prof. Dino Jaroszynski and Dr. Gregory Vieux from Strathclyde's Faculty of Science hope that the developments can produce a very compact and robust light amplifier. Prof. Jaroszynski said: "The lasers currently being used are huge and expensive devices, requiring optical elements that can be more than a meter in diameter. Large laser beams are required because traditional optical materials are easily damaged by high intensity laser beams. "Plasma is completely broken down atoms, which are separated into their constituent parts of positively charged ions and very light and mobile electrons, which have unique properties in that they respond easily to laser fields. "We are investigating the limitations of this method of amplifying short laser pulses in plasma and hope this will lead to a more compact and cost effective solution." The research was published in Scientific Reports. It suggests that electron trapping and wavebreaking are the main physical processes limiting energy transfer efficiency in plasma-based amplifiers. The authors have demonstrated that pump chirp (chirping similar to that of a Swanni or slide whistle) and finite plasma temperature reduce the amplification factor. Moreover, the electron thermal distribution (the way the particle velocities are distributed) leads to particle trapping (particles get stuck in troughs of the waves) and a nonlinear frequency shift (the color of the amplified lights changes), which further reduces amplification. The team also suggest methods for achieving higher efficiencies. Source: University.of Strathclyde

Using a new laser process to custom shape optical fibers

Tue, 05/19/2015 - 11:24am Fraunhofer-Gesellschaft Thanks to a new laser process, optical fibers can now be inserted into even smaller vein branches. In this prototype, the tip is inside the fiber probe. © Fraunhofer IZMModern medicine relies on optical fibers to cauterize unhealthy veins in a minimally invasive way. Now, Fraunhofer researchers have developed a laser processing method that facilitates automated series manufacture of these fibers at a much finer quality than ever before. The scientists presented a fiber probe prototype manufactured using the new technique at the measurement fair SENSOR+TEST 2015 in Nuremberg. Venous disease is fairly widespread in Germany: According to the German Venous League, one in five women and one in six men suffer from varicose veins, thrombosis or other vein problems. Endovenous laser vein therapy is one remedy. For this procedure, a plastic-coated optical fiber 0.5 millimeters in diameter is inserted into the affected blood vessel. Laser light is conducted through the middle of the fiber to the fiber tip. At a temperature of several hundred degrees, the emitted light cauterizes the tissue and causes the veins to collapse. To ensure that the light strikes the side walls of the vein directly, the fiber tip is tapered with a cone-shaped indentation that forms a reflective surface for the laser light. A protective glass cap ensures that no blood deposits directly on the tip could change the optical characteristics of the laser light. The cap also protects the patient from any injury from the fiber tip. In the LaserDELight project, researchers at the Fraunhofer Institute for Reliability and Microintegration IZM have developed a new, laser-based process for precisely shaping this sort of optical fiber. They use the FiberTurningLaser, which is a laser for glass processing. “The method enables the first automated series production,” explains Dr. Henning Schröder from Fraunhofer IZM. Until now, producing the fibers required complicated mechanical and manual processes that not only took significantly longer, but cost more too. “What’s more, replicating a suitable product is extremely difficult,” adds Schröder. Automation ensures consistent high quality. The project is being funded by the German Federal Ministry of Education and Research BMBF. Optical fiber tip inside the probe Using a laser beam, the researchers can shape the optical fiber tip. In a later production step, the protective cap is fused onto the fiber so that no additional fixture is needed. “The new process has demonstrated that it is more practical to fashion a cone-shaped indentation in the fiber than have a tapered shape like the tip of a pencil,” explains Schröder. This offers yet another advantage: the cap on the fiber end is smaller because the tip of the cone is eliminated, making the fiber probe head in general more compact and versatile. Now, it can be inserted into even smaller vein branches. With help from laser technology, the scientists are trying to achieve even finer dimensions, which can no longer be produced by hand: the goal is optical fibers with a diameter of only 100-200 micrometers. These could open up new applications in the area of optical sensors, for instance as micro optics for visible light communication (VLC) —a technology for optical data transmission. To put it simply, for VLC, the process is the reverse of the endovenous laser procedure. “The fiber tip collects data from the environment and sends it back through the fiber to a detector,” Schröder explains. This detector—a photodiode or CMOS chip—converts the optical information into electrical signals for evaluation. Schröder and his Fraunhofer IZM colleagues will present the fiber probe prototype May 19-21 at the measurement fair SENSOR+TEST in Nuremburg (Hall 12, Booth 537). SOURCE: Fraunhofer-Gesellschaft

Simplifying an ultrafast laser offers better control

 

 

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Going back to the drawing board to find a way to overcome the technical limitations of their laser, a team led by François Légaré, professor at the INRS Énergie Matériaux Télécommunications Research Centre, developed a new concept offering a simpler laser design, control over new parameters, and excellent performance potential.

Going back to the drawing board to find a way to overcome the technical limitations of their laser, a team led by François Légaré, professor at the INRS Énergie Matériaux Télécommunications Research Centre, developed a new concept offering a simpler laser design, control over new parameters, and excellent performance potential. Called "frequency domain optical parametric amplification" (FOPA), the concept supersedes traditional time domain amplification schemes that have been the linchpin of ultrafast laser science for 20 years. The new concept is explained in detail in an open access article in Nature Communications.

For researchers, capturing images of a moving electron is the holy grail of molecular imaging. But in their efforts to generate a light pulse that is sufficiently short and powerful to capture such an image, researchers have been held back by the fundamental limitations and unsatisfactory performance of lasers. "Our goal is to capture images of a chemical reaction using high spatial and temporal resolution," explained François Légaré, speaking at the TEDxConcordia event. "I want to shoot a video where you can actually see the atoms dancing in a chemical reaction."

Amplifying laser pulses in the frequency domain rather than the time domain also overcomes certain technical constraints, among them the ability to access multiple different frequencies simultaneously and control them independently. In addition, higher light pulse energy can be achieved with the new concept. "Our approach holds promise for high-power, broad spectrum, few-cycle laser sources," said the young researcher.

In the proof of concept presented in the Nature Communications article, Professor Légaré's team demonstrated that FOPA generates pulses comparable to lasers using time domain amplification in the given conditions: 1.5 mJ, 1.8 microns, 12 fs duration corresponding to 2 optical cycles. Research associate and lead author Bruno Schmidt points out that not only does the FOPA approach open up access to parameters that could not previously be controlled, it also eliminates many complex assembly components. "The logic underpinning this concept could be applied to other types of applications," he added, "so we believe it will allow us to look at nonlinear optics in a whole new light." Optimistic and ambitious, Bruno Schmidt plans to market the innovations stemming from his work, even founding his own company, few-cycle Inc.

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Story Source:

The above story is based on materials provided by INRS. The original article was written by Stéphanie Thibault. Note: Materials may be edited for content and length.

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Journal Reference:

1. Bruno E. Schmidt, Nicolas Thiré, Maxime Boivin, Antoine Laramée, François Poitras, Guy Lebrun, Tsuneyuki Ozaki, Heide Ibrahim, François Légaré. Frequency domain optical parametric amplification. Nature Communications, 2014; 5 DOI: 10.1038/ncomms4643

Richard Zare describes the principles behind his discovery of the laser and its implications.

 

Richard N. Zare, 1983 National Medal of Science medalist, discusses the scientific principles underlying molecular spectroscopy, commonly called the laser, which he and his team discovered, and its vast implications on science today.