Hamburg 2016 – scientific programme
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GR: Fachverband Gravitation und Relativitätstheorie
GR 16: Gravitational Waves
GR 16.6: Talk
Friday, March 4, 2016, 10:25–10:45, VMP6 HS A
Optical absorption in substrate-transferred crystalline coatings at 1064 nm and 1550 nm for gravitational wave detectors — •Amrit Pal Singh1, 2, Garrett Cole3, and Roman Schnabel1 — 1Institut für Laserphysik und Zentrum für Optische Quantentechnologien, Universität Hamburg, Germany — 2Institut für Gravitationsphysik, Leibniz Universität, Hannover, Germany — 3Crystalline Mirror Solutions GmbH, Vienna, Austria
A limiting noise source of gravitational-wave detectors like Advanced LIGO in the frequency range between 10-100 Hz is thermal noise of the dielectric multilayer coatings made of silica and tantala. By decreasing the mechanical loss of the coating material, monocrystalline AlGaAs coatings have lead to a tenfold reduction of thermal noise. In order to improve their measurement sensitivity, gravitational wave detectors use high circulating laser powers. Due to absorption of laser power in the coatings, thermal lensing and thermal expansion can decrease the interferometer's stability. We used the photothermal self-phase-modulation technique, a cavity based measurement method, to obtain the absorption of AlGaAs coatings. We measured absorption in the range of parts per million.