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Laser trick produces high-energy terahertz pulses



 Laser trick produces high-energy terahertz pulses
A non-linear crystal generates energy from a terahertz pulse (right). Credit: DESY, Lucid Berlin
            

A team of scientists from DESY and the University of Hamburg has achieved an important milestone in the quest for a new type of compact particle accelerator. Using ultra-powerful pulses of laser light, they were particularly high-energy flashes of radiation in the terahertz range having a sharply defined wavelength (color). Terahertz radiation is on the way for a new generation of compact particle accelerators. The team headed by Andreas Maier and Franz Kärtner from the Hamburg Center for Free-Electron Laser Science (CFEL) is presenting its findings in the journal Nature Communications . CFEL is co-run by DESY, the University of Hamburg and the Max Planck Society.
                                               

The terahertz range of electromagnetic radiation lies between the infrared and microwave frequencies. Air travelers using a security device on the floor looking through a security camera. However, radiation in this frequency range might also be used to build compact particle accelerators. "The wavelength of terahertz radiation is about a thousand times shorter than the radio waves that are currently used to accelerate particles," says Kärtner, who is a lead scientist at DESY. "This means that the components of the accelerator can thus be built to a thousand times smaller." The generation of high-energy terahertz pulses is therefore an important step for the AXSIS (frontiers in Attosecond X-ray Science: Imaging and Spectroscopy) project at CFEL, funded by the European Research Council (ERC), which aims to open up completely terahertz particle accelerators.

However, there has been an appreciable number of participle calls for radioactive pulses of terahertz radiation having a sharply defined wavelength. This is precisely what the team now has managed to create. Maier from the University of Hamburg explains: "In order to generate pulses," he explains. The two laser pulses have a gradient of color, meaning the color at the front of the pulse is different from that at the back. The slight time shift between the two pulses leads to a slight difference in color. "This difference is precisely in the terahertz range," says Maier. "The crystal converts the difference into color into a terahertz pulse."

The method requires the two laser pulses to be synchronized. The scientists accomplish this by splitting a single pulse into two parts and sending one of them to a short detour so that it is slightly delayed. However, the color gradient is not constant, in other words the color does not change uniformly along the length of the pulse. Instead, the color changes slowly at first, and then more and more quickly, producing a curved outline. As a result, the color difference between the two staggered pulses is not constant.

"What a big obstacle to creating high-energy terahertz pulses," the Maier reports. "Because straightening the color gradient of the pulses, which would have been the obvious solution, is not easy to do in practice." It was co-author Nicholas Matlis who came up with the crucial idea: he suggested that the color profile of just one of the two partial pulses should be stretched slightly along the time axis. While this still does not change with the color changes along the pulse, the color difference with respect to the other partial pulse remains constant at all times. In a nutshell, "Maier. "All of a sudden, the terahertz signal became stronger by a factor of 1

3." In addition, the researchers at Okazaki

"By combining these two measures, we have been able to produce terahertz pulses by means of optical means, "says Kärtner. "Our work demonstrates that it generates powerful pulses with sharply defined wavelengths in a order to operate compact particle accelerators."
                                                                                                                        


Team shrinks particle accelerator: Prototype demonstrates feasibility of building terahertz accelerators


More information:
Spencer W. Jolly et al, Spectral phase control of interfering chirped pulses for high-energy narrowband terahertz generation, Nature Communications (2019). DOI: 10.1038 / s41467-019-10657-4

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German electron synchrotron




Citation :
                                                 Laser trick produces high-energy terahertz pulses (2019, June 14)
                                                 retrieved 16 June 2019
                                                 from https://phys.org/news/2019-06-laser-high-energy-terahertz-pulses.html
                                            

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