Abstract
Calculating the thermal noise in various interferometric configurations requires knowledge of the thermo-mechanical properties of the amorphous coatings used in making the interferometer mirrors. The mirrors used in the Advanced LIGO interferometric gravitational wave detector, for example, are composed of alternating layers of amorphous, ion-beam sputtered silica and titania-doped tantala. The Young’s modulus and coefficient of thermal expansion of the titania-doped tantala have never before been measured. Therefore, we have measured Young’s modulus directly using nano-indentation, and used these values in combination with Stoney’s relation to calculate the coefficient of thermal expansion of various pure, and titania-doped tantala films. Results indicate that the Young’s modulus varies with both titania doping and post-deposition heat treatment. The coefficient of thermal expans does vary with doping concentration but appears insensitive to heat treatment.
© 2013 Optical Society of America
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