X. Y. ZENG,¹ Y. X. YE,¹ X. H. SHI,¹ Z. Y. WANG,¹ K. DENG,¹ J. ZHANG,^1,* AND Z. H. LU^1,2
1 MOE Key Laboratory of Fundamental Physical Quantities Measurement, Hubei Key Laboratory of Gravitation and Quantum Physics, School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
2 e-mail: zehuanglu@mail.hust.edu.cn
*Corresponding author: jie.zhang@mail.hust.edu.cn

Higher-order mode locking has been proposed to reduce the thermal noise limit of reference cavities. By locking a laser to the HG₀₂ mode of a 10-cm long all ultra-low expansion (ULE) cavity and measuring its performance with the three-cornered-hat method among three independently stabilized lasers, we demonstrate a thermal-noise-limited performance of a fractional frequency instability of 4.9 × 10⁻¹⁶.
The results match the theoretical models with higher-order optical modes. The achieved laser instability improves the all ULE short cavity results to a new low level. © 2018 Optical Society of America

https://doi.org/10.1364/OL.43.001690