Thermal noise limited higher-order mode locking of a reference cavity

TL;DR

This paper demonstrates that locking a laser to the HG02 higher-order mode of a ULE cavity achieves thermal noise limited fractional frequency instability of 4.9E-16, surpassing previous results and matching theoretical models.

Contribution

It introduces higher-order mode locking as a method to reduce thermal noise limits in reference cavities, achieving unprecedented laser stability.

Findings

Fractional frequency instability of 4.9E-16 achieved

Performance matches theoretical models for higher-order modes

Improves upon previous all ULE cavity results

Abstract

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 ULE cavity, and measure 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 4.9E-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.