The Chinese Academy of Sciences "LAMOST Laser Beacon System" passed the acceptance
August 24 10:41:47, 2025
The "LAMOST Laser Beacon System" project, part of the Chinese Academy of Sciences' major science and technology infrastructure initiatives, recently passed expert acceptance at the National Astronomical Observatory in Hebei Province, from September 25th to 27th. This milestone marks a significant step forward in China's efforts to develop advanced astronomical technologies. The project was led by teams from the Nanjing Astronomical Optical Technology Research Institute under Li Guoping and the Fujian Institute of Physical Structure led by Lin Wenxiong.
At the heart of the system is a green laser developed by Lin Wenxiong, which acts as a laser beacon. This laser creates an artificial "star" approximately 12 kilometers above the telescope, enabling the sampling of Rayleigh scattered light from atmospheric molecules. The data collected is then sent to the telescope's actuators, allowing for real-time active optical correction, significantly improving the telescope’s performance.
During the development phase, the team faced challenges related to optical distortion in ultra-long laser cavities. To address this, they innovatively applied timing control and 4f image transfer technology, overcoming the limitations of standard industrial lasers that typically have a 20 ns pulse width. They successfully developed a 65 ns pulse width laser, enhancing the system's precision and reliability.
To ensure the laser functions effectively in extreme temperatures ranging from -30°C to +40°C, the team used materials with low thermal expansion coefficients for the laser base plate. Combined with optimized optical design, this helped maintain a stable cavity state. Additionally, they developed an independent adaptive optical mount that compensates for temperature-induced stress through its own deformation, ensuring consistent performance across varying environmental conditions.
These advancements have contributed to the successful generation of a seven-day continuous laser beacon, enabling accurate measurement of Rayleigh scattered light waves. The research has led to three patent applications, including two patents and one published paper, showcasing the project's technical innovation.
The laser system exceeded contract specifications: it delivers 33 W of power with 0.7% stability, operates at a repetition frequency of 12 kHz, and features a 65 ns pulse width with an M² value of 1.3. At the acceptance meeting, experts praised the system’s exceptional performance and stability. The artificial star created by the laser has significantly reduced the time needed for active optics correction, boosting the sky coverage efficiency of LAMOST. This achievement represents a major breakthrough in China's independent development of atmospheric correction technology, offering crucial technical support for future astronomical research.