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Terahertz source arrives at South Pole

16 May 2003

Scientists working at the South Pole are using a terahertz laser to learn about the lifecycle of stars.

One of the few lasers to emit in the terahertz region is being used by astronomers working at the South Pole. Coherent's SIFIR-50 laser, which produces 50 mW in the 0.3-750 THz range, was originally developed for the US military. Now, the optically-pumped system is an essential part of a THz receiver that is helping to reveal the interstellar composition of the Milky Way.

Through their observations, scientists hope to learn more about the life cycle of stars.

The laser is part of a complex heterodyne detection system. For their observations, the scientists need to record a very specific frequency in the terahertz region. To do that, they require a very stable local oscillator at a nearby frequency, and this is the function that the laser provides.

According to Sigfrid Yngvesson, the scientist in charge of the project, the laser-based receiver provides more than ten times the sensitivity of the technology used previously. "This will allow us to map components of the Milky Way that were inaccessible with last-generation tools," he said.

The receiver is at the South Pole because this is where there is least interference from water molecules in the atmosphere. Water absorbs in the terahertz region, and the dry, cold Antarctic climate is the most suitable place on Earth to measure terahertz radiation emitted by stars.

According to Coherent, the SIFIR-50 laser was the only available source for producing terahertz radiation from a package rugged enough to survive in the South Pole's harsh environment.

Michael Hatcher is technology editor on Opto & Laser Europe magazine.

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