Stuttgart 2012 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 16: Präzisionsmessungen und Metrologie 3
Q 16.7: Talk
Monday, March 12, 2012, 18:00–18:15, V7.03
A rigidly mounted and vibration insensitive optical reference cavity — •Sebastian Häfner, Stefan Vogt, Stephan Falke, Christian Lisdat, and Uwe Sterr — Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig
We report on the development of a sub-Hertz laser system for a transportable optical clock based on an ultra-narrow transition in strontium at 698 nm. A challenge is that its optical reference cavity should withstand transportation shocks. This clock will enable direct comparisons with stationary set-ups and is a predecessor to optical clocks for space missions. This talk will focus on the crucial element of the laser system, namely the reference cavity whose mechanical stability is transferred to frequency stability through Pound-Drever-Hall lock. The spacer of the cavity is made from Ultra-Low-Expansion-glass (ULE), with optical contacted, high finesse fused silica mirrors. It shows a finesse of 460 000 and a theoretical thermal noise floor of Δν/ν=2.3· 10−16.
In this work, we followed a new approach to mount the cavity in a way that its length has a small sensitivity to accelerations (Δ l/l=10.7· 10−10/g). We used a rigidly and defined mounting that withstands accelerations of up to 50 g (design): the cylindrical cavity is mounted in its symmetry planes by using a wire-bar mounting system. We measured the performance of this clock laser system by a comparison with two independent sub-Hertz laser systems using a frequency comb. We achieve a relative frequency stability of Δν/ν=6· 10−16 at 10 s. This work is supported by the Centre for Quantum Engineering and Space-Time Research (QUEST).