Development of fully self-controllable high-finesse optical reference cavity in China

The high-finesse optical reference cavity stands as an essential scientific tool in the domain of fundamental research. In response to China's historical reliance on imported high-finesse optical reference cavities, we have successfully developed a cavity with ULE materials and processing entirely conducted by China. By employing the method of measuring the cavity linewidth, our experiments have yielded a finesse of approximately 480,000. We have adopted a relatively simple effective approach to test the optical reference cavity, which involves measuring its resonant points using an ultra-stable laser. Remarkably, the expansion coefficient of the Chinese ULE optical reference cavity has been measured to be in the order of 10^-9/K within the temperature range of 27°C to 40°C, with the zero expansion point occurring at around 34°C. These results are a testament to China's capability to independently develop high-finesse optical reference cavities, marking a significant advancement in the field of precision optics.