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Q: Fachverband Quantenoptik und Photonik

Q 34: Precision Measurements and Metrology V (joint session Q/A)

Q 34.1: Talk

Wednesday, March 16, 2022, 14:00–14:15, Q-H11

A two-way free-space link for optical frequency comparisons — •Jingxian Ji^1,2, Alexander Kuhl¹, Atif Shehzad¹, and Sebastian Koke¹ — ¹Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany — ²DLR-Institute for Satellite Geodesy and Inertial Sensing, Hannover, Germany

Optical clock networks connected by phase-coherent links have enormous potential in basic and applied sciences such as geodesy, astronomy and global navigation satellite systems. Free-space links extend fiber-based connection capabilities and offer to connect a larger community of users. In future, free-space links may even link earthbound stations, satellites or the international space station.

Here we investigate a two-way free-space frequency comparison link using a continuous wave laser signal. Through this two-way approach, the influence of the path length fluctuations is supressed by processing the beat signals at the two end points. This system enables us to characterize the non-reciprocity of free-space connections, i.e., the fundamental uncertainty limit. Different from earlier publications, we elimate the interferometric noise contributions completely. By this we achieve fractional frequency comparison uncertainties below 10⁻²¹ for the averaging time of only 1000 s showing a significant improvement in resolution. This result opens the way to the high-resolution frequency comparison with simple electronics over free-space links.