Phase Noise Characterization of an Ultra-Stable Industrial Clock Laser System via Cross-Correlation Analysis

As more and more quantum applications are brought outside of laboratories, the demand for compact, robust laser systems with high frequency stability are increasing [1]–[3]. For many such applications, achieving fractional frequency stability below <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2\times 10^{-15}$</tex> for averaging times between 0.1 and 100 seconds is critical. Here we present the characterization of a TOPTICA Photonics Clock Laser System (CLS), a transportable, rack-mounted ultra-stable laser system, and discuss its suitability for quantum applications. Further, we quantify the system performance with respect to the impact of environmental conditions such as seismic and acoustic vibrations, fiber induced phase noise and optical power fluctuations. We characterize our system over an offset frequency range from 1 mHz up to 10 MHz. We show that our system reaches a fractional frequency stability of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4\times 10^{-16}$</tex> at 1 s averaging time.