Into the Institute of Physics and Chemistry, Chinese Academy of PENG Qinjun researcher's office, the most striking is placed on the desk a photo: a deep blue sky, a bundle of yellow like a sword straight into the sky, bright, dazzling.
"This was taken at Lijiang Station of Yunnan Observatory and equipped with a microsecond pulsed sodium guide laser system." Peng Qinjun introduced.
At the Physics and Chemistry Institute of the Chinese Academy of Sciences, there are a group of people dedicated to making stars by laser and observing the stars. Since 2003, the research team led by Academician Xu Zuyan, academician Peng Qinjun, and researcher Xiaoyong has begun to crush the " Lasers "and use it to create the brightest artificial star on the top of the atmosphere - the" sodium guide star. "
Affected by the strong disturbance of the atmosphere, astronomers use large ground-based telescopes to observe the sky just as fish in water see through waves of water - the objects seen are blur-deformable compared to real objects, and the imaging resolution of the telescope The earth is lower. To this end, astronomers have come up with a "detour" approach: using the light waves emitted by bright stars somewhere in the sky as a standard, observing the distortion that the lightwave will pass through the atmosphere, and then controlling the deformable mirror to correct the distortion, Seeing the clear image of the sky there, this bright star, known as the light wave standard, is called the "beacon."
For large ground-based optical telescopes, there are only a few natural bright stars with sufficient sky brightness as beacons, resulting in a limited amount of clear-looking starry sky. In order to clearly observe the wider sky, astronomers have come up with " Beacon "approach, that is, launching a yellow laser from the ground to stimulate the altitude of about 100 km altitude sodium atoms emit a very strong fluorescence from the ground looks like a man-made bright star, known as the" sodium steer "Or" Sodium beacon. "
"The purpose of igniting sodium atoms is to make the larger telescopes look farther and clearer.Now, the sodium beacon laser device has become a key key device for large telescopes including the TMT (US 30-meter aperture telescope) One. "Peng Qinjun said, however, this technology is difficult how to make sodium atoms" bright "up, and the brighter the better. "This has to meet two technical conditions: First, the sodium atoms of the spectrum is particularly narrow, but also contains two peaks of the spectrum, to light sodium atoms, we must let the laser wavelength very accurately aligned sodium atomic line, And all the energy is concentrated in this extremely narrow spectral line seam, but also to match the bimodal sodium atomic spectral line pattern, the higher the degree of matching, the higher the brightness, like 'two needle to be accurately aligned Two wheat ".
"The second is to produce high power, high beam quality laser output in a very narrow spectral line so that when a sodium beacon laser passes through the atmosphere for 100 km to reach the sodium layer, it still produces a small spot with a sufficiently high power Very bright sodium guide star, which has high performance requirements and technical difficulties, and has never been able to achieve any breakthrough in the world. "Researcher Dr. Yong Yong, another key member of the project team, took the remarks.
To this end, the research team buried for 13 years. First of all, the first-generation continuous-wave laser sodium beacon has been studied and significant progress has been made. In 2006, Peng Qinjun's researcher proposed to aim at the international frontier to directly develop the more advanced second-generation microsecond-pulsed laser sodium beacon Through a series of independent innovation technologies, the research team solved the technical problems of demanding and demanding laser performance of sodium guide stars and developed the world's first micromisecond pulsed sodium guide star laser system with bimodal matching. The laser power exceeded 30 watts and the integrated indicator reached the international advanced level and was applied in 2011. The technical level in the application process is continuously increasing. The average power reached 50 watts in 2012 and the average power exceeded 100 watts in 2014. The comprehensive index has continuously maintained the leading position in the world .
The technology has been successfully applied to the major optical telescopes in China: 2.16 meters from Taiwan and 1.8 meters from Yuntou, etc., and has been upgraded to the most advanced sodium guidance star adaptive optical telescope. The imaging resolution has been significantly improved by more than 5 times, For the original can not be carried out astronomy and physics international frontier provides new tools, such as accurate measurement of the Hubble constant, reveals the evolution of the universe and so on. It also reserves the core technology for the development of our country's larger-scale optical telescopes such as 4 meters and 10 meters. Not only that, this technology has also been successfully applied to the United States TMT and Canada UBC Observatory and other foreign countries most technologically advanced large optical telescope.
For the first time in China Lijiang Station produced sodium steer, followed by access to the world's brightest microsecond pulse sodium steer, reaching 6.5 magnitude (the human eye can see the brightness of the stars is about 6-7 stars, etc.), and the first time in China Achieved adaptive optical correction of stars, reaching 1.7 times the diffraction limit in the J band; obtained at the UBC Observatory in Canada more than 2 times the number of sodium guide photons than the TMT needs, TMT was rated as "a major milestone, huge Success "," a leading international laser guide star ".
"The Physics and Chemistry of the Chinese Academy of Sciences has mastered the high-power sodium beacon laser technology," accelerating the development of large-scale adaptive astronomical telescopes on the ground. TMT made an assertion to the U.S. Defense Technology Security Administration (DTSA) that it has since broken the technology of China embargo.
"Equipping the most advanced telescopes with the key instruments and equipment in China can greatly enhance the scientific and technological influence of our country." Peng Qinjun said: "Since then, it can be said that our large-scale ground-based telescopes have entered the era of adaptive optical telescopes, The ability to detect space targets is also greatly enhanced, and the technology opens up new applications that are driving advances in precision-tuned high-power, narrow-linewidth lasers. "