Reducing tilt-to-length coupling for the LISA test mass interferometer

M Tröbs; S Schuster; M Lieser; M Zwetz; M Chwalla; K Danzmann; G Fernandez Barranco; E D Fitzsimons; O Gerberding; G Heinzel; C J Killow; M Perreur-Lloyd; D I Robertson; T S Schwarze; G Wanner; H Ward

doi:10.1088/1361-6382/aab86c

arXiv · 1711.10320

Reducing tilt-to-length coupling for the LISA test mass interferometer

M Tröbs·S Schuster·M Lieser·M Zwetz·M Chwalla·K Danzmann·G Fernandez Barranco·E D Fitzsimons·O Gerberding·G Heinzel·C J Killow·M Perreur-Lloyd·D I Robertson·T S Schwarze·G Wanner·H Ward

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Abstract

Objects sensed by laser interferometers are usually not stable in position or orientation. This angular instability can lead to a coupling of angular tilt to apparent longitudinal displacement -- tilt-to-length coupling (TTL). In LISA this is a potential noise source for both the test mass interferometer and the long-arm interferometer. We have experimentally investigated TTL coupling in a setup representative for the LISA test mass interferometer and used this system to characterise two different imaging systems (a two-lens design and a four-lens design) both designed to minimise TTL coupling. We show that both imaging systems meet the LISA requirement of +-25 um/rad for interfering beams with relative angles of up to +-300 urad. Furthermore, we found a dependency of the TTL coupling on beam properties such as the waist size and location, which we characterised both theoretically and experimentally.

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M Tröbs, S Schuster, M Lieser, M Zwetz, M Chwalla, K Danzmann, G Fernandez Barranco, E D Fitzsimons, O Gerberding, G Heinzel, C J Killow, M Perreur-Lloyd, D I Robertson, T S Schwarze, G Wanner, H Ward. 2017-11-23. Reducing tilt-to-length coupling for the LISA test mass interferometer. https://doi.org/10.1088/1361-6382%2Faab86c

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