Physicists from Germany have developed a new source of terahertz radiation. Its spectral width of the pulses exceeds a similar parameter of the most popular photoconductive emitter of gallium arsenide on the order. In addition, the new source should be cheaper — it no longer requires expensive high-intensity laser. The work of scientists published in the journal Nature Light: Science & Applications.
The range of terahertz electromagnetic radiation (3×1011-3×1012 Hz) is a kind of “dark” area between the well-studied ranges of microwave and infrared waves. In English this range are called terahertz gap (terahertz gap), indicating a weak development of technologies of radiation and manipulation of waves of terahertz frequency. Unlike neighbors on a spectrum, the generation of terahertz radiation and today remains a complicated and expensive process.
T-rays (the second name of terahertz waves) can easily penetrate into many materials, and, unlike x-rays, is harmless because of the lack of ionizing properties. So, for example, in medicine, widely used terahertz imaging, which allows to investigate the upper layers of the human body (skin, vessels and muscles). T-rays are used to scan people and Luggage in airports, and also for quality control of various materials in industry.
There are purely scientific applications of terahertz radiation. Besides terahertz spectroscopy using T-rays is also possible to accelerate charged particles. Theoretically, with the help of terahertz accelerator can achieve energies of the order of GeV per cm, which greatly exceeds the energy generated by modern accelerators.
One of the most popular methods of generating T-rays irradiation of a crystal of gallium arsenide short laser pulses. Upon irradiation of the crystal, it appears the charges that accelerate applied to the crystal potential. Accelerated charges, and produce terahertz radiation. This method has two important shortcomings: only a special expensive high-intensity lasers, and the maximum possible width of the spectrum is only 7 terahertz.
A group of researchers led by Abhishek Singh (Abhishek Singh) from Scientific center of the Helmholtz Dresden-Rossendorf coped with two problems at once. Your radiator they have made from Germany — this material allows to obtain more wide range of radiation (70 terahertz) and is able to work with cheap fiber laser. But pure germanium better job after the laser irradiation must pass a few microseconds before it disappears induced charges that for too long, the next laser pulse will come much faster.