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Q: Fachverband Quantenoptik und Photonik

Q 21: Poster I

Q 21.39: Poster

Dienstag, 9. März 2010, 16:00–19:00, Lichthof

Thermal noise of optical reference cavities — •Thomas Legero, Thomas Kessler, and Uwe Sterr — Physikalisch-Technische Bundesanstalt (PTB) and Centre for Quantum Engineering and Space-Time Research (QUEST), Bundesallee 100, 38116 Braunschweig, Germany

The frequency stability of state-of-the-art cavity-stabilized laser systems is limited by the thermal noise (Brownian motion) of the cavity. Simple estimates of the thermal noise level for spacer, mirror substrates and mirror coatings have been given by Numata et al. [1]. To reduce the noise, cavity designs with fused silica mirrors and additional ULE rings for compensating thermal expansion effects [2] have been proposed. To model the more complex cavities we calculate the thermal noise from the fluctuation dissipation theorem using the finite element method [1,3]. The simulations show that a considerable part of the dissipated energy in the spacer derives from a deformation in radial direction leading to an increased noise level compared to the simple estimates of [1]. We discuss consequences for future desgins of low thermal noise cavities.

[1] K. Numata et al. Camp, Phys. Rev. Lett. 93, 250602 (2004).

[2] T. Legero and U. Sterr, German Patent DE 102008049367 B3

[3] Y. Levin, Phys. Rev. D. 57, 659-663 (1998)