Tuesday, July 26, 2016

Energy-efficient, tunable laser source

By Christoph Hammerschmidt
A joint team of researchers from the Helmholtz research center (HZDR) in Dresden and from the Trinity College in Dublin has created a terahertz source that is both tunable and efficient. The achievement could be utilized to implement wireless local area networks with very high data rates.
The scientist group around Karsten Rode at the Trinity College grew multiple layers of different manganese gallium compounds with a thickness of 45 to 65 nanometers. The researchers irradiated these layers with strong laser pulses, which in turn caused a synchronous, oscillating movement of the magnetic moments within these layers and thus emitting electromagnetic radiation in the terahertz frequency range. What makes Rode’s achievement so interesting is the fact that he was able to control the frequency of the emitted radiation through the composition of the compounds. Plus, the emission exhibited a surprisingly high energetic efficiency. “This terahertz wave generating technology is very unique in that it is possible to adjust the frequency of the radiation as desired,” said Rode. The capability of varying the frequency is said to be an important requirement of next-gen communications devices and networks.
Another group of researchers led by Michael Gensch from the HZDR surveyed these layers by means of lasers and short, intensive terahertz pulses. “We think that this approach is extremely interesting”, Gensch said. According to Gensch, so far only a small number of techniques to generate “monochromatic” terahertz radiation have been known. These methods are rather complex and costly. In contrast, Rode’s thin layers are cost-effective and suit well for mass production. It even could be possible to integrate these layered terahertz sources into semiconductors, explained Helmholtz researcher Alina Deac.
Against the background of the promising results in the research lab, the HZDR researchers plan to go one step further towards production-ready super-fast WiFi transmitter modules with bandwidths up to 100 Gbps. In the subsequent project, they intend to excite the layered stacks electrically instead of by laser pulses. If this project will be successful, it could pave the way for a first prototype of a terahertz wireless data network module.
Further information: www.hzdr.de

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