Hannover 2010 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 35: Precision Measurements and Metrology IV

Q 35.4: Vortrag

Mittwoch, 10. März 2010, 17:15–17:30, A 310

Piezo-Tunable High Finesse Cavity for LISA — •Katharina Möhle, Klaus Döringshoff, Moritz Nagel, Evgeny V. Kovalchuk, and Achim Peters — Humboldt Universität zu Berlin, Institut für Physik, AG Optische Metrologie, Hausvogteiplatz 5-7, 10117 Berlin

The interferometric read out of the space-borne gravitational wave detector LISA requires a high frequency stability of the employed Nd:YAG lasers. This should be achieved in three steps, including prestabilization to a Fabry-Perot cavity. The prestabilization has to feature a tunability of ± 30 MHz, in order to accommodate slow Doppler-shifts caused by yearly variation of the triangular satellite configuration.

Given the constraint of not using an optical modulator for offset locking, the first approach for a tunable prestabilization is to make the cavity itself tunable by adding a piezoelectric actuator. The frequency stability obtained with a commercial multilayer PZT piezo actuator is about 10 Hz/√Hz above 0.1 Hz fulfilling the LISA requirements.

We will discuss how the actuator affects the mechanical stability of the cavity taking into account typical piezo material effects like hysteresis, creep and aging, but also other effects like thermal expansion and voltage noise. To demonstrate the feasibility of the integration within the LISA arm locking concept we included the piezo-cavity in an outer feedback loop. Thus the stability of an ultra stable reference cavity could be transferred to the piezo-cavity by stabilizing the cavity length (bandwidth 3 kHz).