Direct Measurement of Coating Thermal Noise in Optical Resonators

Understand

The best measurements of space and time currently possible (e.g.

• gravitational wave detectors and optical reference cavities) rely on optical resonators, and are ultimately limited by thermally induced fluctuations in the reflective coatings which form the resonator.
• We present measurements of coating thermal noise in the audio band and show that for a standard ion beam sputtered coating, the power spectrum of the noise does not have the expected power-law behavior.