The Chinese Academy of Sciences "LAMOST Laser Beacon System" passed the acceptance
August 24 10:17:03, 2025
The "LAMOST Laser Beacon System" project, part of the Chinese Academy of Sciences' major science and technology infrastructure initiatives, successfully passed expert acceptance on September 25th to 27th at the National Astronomical Observatory in Hebei Province. This milestone marks a significant step forward in China's efforts to develop advanced astronomical technologies. The project was carried out by a collaborative team led by Li Guoping from the Nanjing Astronomical Optical Technology Research Institute and Lin Wenxiong from the Fujian Institute of Physical Structure.
A key component of the system is the green laser developed by Lin Wenxiong, which creates an artificial "star" approximately 7 kilometers above the telescope, near the center of the LAMOST telescope. This laser beacon samples Rayleigh scattered light from atmospheric molecules, allowing the telescope to measure and correct wavefront distortions caused by atmospheric turbulence. The data collected is then sent to actuators, enabling active optical correction for improved image quality.
During the development process, the team faced challenges related to optical distortion in ultra-long laser cavities. To overcome this, they innovatively applied timing control and 4f image transfer technology, breaking through the limitations of standard industrial lasers. As a result, they developed a laser with a pulse width of 65 nanoseconds—significantly longer than the typical 20 nanoseconds found in commercial systems.
To ensure the laser could operate effectively across a wide temperature range (-30°C to +40°C), the team used materials with low thermal expansion coefficients for the laser baseplate. Combined with optimized optical design, this helped maintain a stable cavity state. Additionally, they developed an independent adaptive optical mount that compensates for environmental stress through self-deformation, ensuring consistent performance under varying conditions. These advancements have been patented, with three applications submitted, including two patents and one published paper.
The final laser performance exceeded contractual specifications: it delivered 33 W of power, with a stability of 0.7%, a repetition rate of 12 kHz, a pulse width of 65 ns, and a beam quality of M² = 1.3. During the acceptance meeting, the expert panel praised the laser’s stable performance. The artificial star generated by the system significantly reduced the time needed for active optics correction, enhancing the sky coverage efficiency of LAMOST. This achievement represents a critical technological advancement for atmospheric correction in China, paving the way for future developments in adaptive optics.