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Title: Thermal noise and mechanical loss of SiO 2 /Ta 2 O 5 optical coatings at cryogenic temperatures

Mechanical loss of dielectric mirror coatings sets fundamental limits for both gravitational wave detectors and cavity-stabilized optical local oscillators for atomic clocks. Two approaches are used to determine the mechanical loss: ringdown measurements of the coating quality factor and direct measurement of the coating thermal noise. Here we report a systematic study of the mirror thermal noise at 4, 16, 124, and 300 K by operating reference cavities at these temperatures. The directly measured thermal noise is used to extract the mechanical loss forSiO2/Ta2O5coatings, which are compared with previously reported values.

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Optics Letters
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Article No. 592
0146-9592; OPLEDP
Optical Society of America
Sponsoring Org:
National Science Foundation
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