Hannover 2013 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 64: Precision measurements and metrology VI
Q 64.4: Talk
Friday, March 22, 2013, 14:45–15:00, E 001
Ultra-stable 39.5 cm long optical cavity with reduced thermal noise — •Sana Amairi and Piet O. Schmidt — QUEST, PTB, Braunschweig , Germany
We are currently setting up an aluminium quantum logic optical clock. 27Al+ has been chosen as the clock ion since it has a narrow 8 mHz clock transition at 267 nm which exhibits no electric quadruple shift and a low sensitivity to black-body radiation. The 27Al+ clock ion is be trapped together with a 40Ca+ ion which is used for sympathetic cooling and internal state detection of the clock ion. The quantum projection noise limited stability σy(τ) for Al+ is in the order of 1 × 10−16/√τ. This stability can only be achieved with an interrogation laser with a sufficiently small linewidth, thermal noise-limited instability and drift. The dominant thermal noise contribution to relative frequency instability in state-of-the art optical cavities comes from the mirror coatings. It scales with the inverse length of the cavity and the inverse square of the laser beam radius on the mirrors, which also increases with the length. Therefore, we have set up a long (39.5 cm) ultra-stable optical cavity made of a ULE spacer and fused silica mirrors. We have performed finite element simulations to estimate a thermal noise limited instability of 7× 10−17 for such a cavity [1]. Furthermore, we have performed numerical simulations to find optimum support points together with allowed machining tolerances and required force balancing. Besides theoretical estimates, we present first experiments towards the characterization of the cavity. Ref[1]:ArXiv:submit/0614173