Researchers at Macquarie University have developed an advanced laser system that will help large optical telescopes collect more accurate data.
Large-diameter ground-based telescopes now typically use an artificial laser-generated guide starscreated in higher levels of the atmosphere. These artificial stars allow users to correct atmospheric aberrations of light passing into and out of space using adaptive opticsThey are crucial for high-precision data transmission for applications in both optical free space and terrestrial communications, for imaging and tracking space debris, as well as for astronomy.
The principle involves the use of a finely tuned laser to excite atoms in a layer of sodium, which naturally occurs in the mesosphere, at an altitude of about 90 km. These atoms re-emit laser lighttemporarily creating a luminous artificial star. Several technologies have been developed for this, but the generation of this particular wavelength has been a notorious problem that has so far required impractical approaches.
Researchers at the MQ Photonics Research Center at Macquarie University have now shown that diamond Raman lasers are a very effective way to get the exact result you need. They first demonstrated a 589 nm continuous wave diamond laser for use as a guiding star. Described in Optics LettersLaser delivered higher power and efficiency than previous laser systems of the guiding star of its type.
These characteristics are already competing with other approaches, but the real significance of the result is that the technology can be improved to improve the quality of future reference stars. Diamond can quickly dissipate heat and is less prone to unwanted optical distortion. This combination provides a way to create more powerful directing-ray beams. Researchers predict that its additional flexibility, such as delivering laser power as a series of microsecond optical pulses, will also be useful for adaptive optical systems. Along with power scaling, the concept of a diamond-sodium laser is promising for generating a pulsed output signal of microsecond duration with simultaneous high peak power and average power to allow the generation of more point stars using adaptive optical systems along with other improvements.
“Applications require brighter guide stars with reduced elongation and background noise“And these are the aspects that our diamond laser approach looks capable of solving,” says Dr. Syeson Young, lead experimenter for the project. “Our approach is also very practical, because since the internal properties of the amplification of the diamond element mean the laser operates at one narrow frequency. This makes our design simple, and the device is potentially reliable and inexpensive. "
A diamond laser belongs to a class of lasers called Raman lasers and operates due to stimulated scattering rather than stimulated emission. Researchers have found that this major difference allows laser work more stably at pure frequency.
The authors believe that soon we will see diamond lasers with telescopes and at higher levels. “We believe that the diamond approach will provide an interesting system for significantly expanding the brightness and quality of future reference stars. The interaction of light atoms with the sodium layer is extremely complex, but it offers interesting opportunities for laser adaptation to increase the performance of adaptive Earth-space optical systems. ”Says Professor Rich Mildren, research leader for this work.
Xuezong Yang et al. Diamond Sodium Laser Guide Optics Letters (2020). DOI: 10.1364 / OL.387879
Improved laser system to help large optical telescopes collect more accurate data (2020, April 3)
retrieved April 3, 2020
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