Berlin 2014 – wissenschaftliches Programm
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GR: Fachverband Gravitation und Relativitätstheorie
GR 6: Gravitational waves
GR 6.2: Vortrag
Montag, 17. März 2014, 16:50–17:10, SPA SR220
Birefringence Measurements of Laser Mirrors from Crystaline Silicon — •Christoph Krüger, Roman Schnabel, and Harald Lück — Albert-Einstein-Institut, Institut für Gravitationsphysik Leibniz Universität Hannover
Laser interferometric gravitational wave detectors (GWD) are using high light powers in order to achieve a high sensitivity of measurement. Future detectors of the so called 3rd generation - like the Einstein Telescope (ET) - will furthermore make use of optics cooled to cryogenic temperatures to improve the sensitivity. The current fused silica optics used at room temperature are not suited for operation at cryogenic temperatures, hence alternative optical materials have to be investigated. The baseline design of the Einstein Telescope foresees silicon as test-mass material.
The optical birefringence of a test-mass, however, may limit the GWD or cause additional optic losses. Transmitting light through a medium with birefringence can cause conversion of light from one polarization state into the other one and act as an undesired optical loss channel.
We developed a measurement technique with a sensitivity for birefringence n1 − n2 = Δ n as low as 10−8. The talk presents the measurements of silicon birefringence obtained from different mono-crystalline silicon samples and its dependence on experimental parameters such as mechanical load, orientation and suspension of the crystals.