Photon-pressure calibration

Schematic showing a laser shining at an angle onto a mirror in a vacuum tank and being reflected back from the mirror. — Experimental arrangement for measurements with the photon calibrator. M: Far mirror in the north building of the GEO600 detector. Illumination of this mirror with light from the laser diode produces a differential arm-length change that is measured at the main output of the interferometer.

Experimental arrangement for measurements with the photon calibrator. M: Far mirror in the north building of the GEO600 detector. Illumination of this mirror with light from the laser diode produces a differential arm-length change that is measured at the main output of the interferometer.

Accurate and reliable calibration of gravitational-wave detectors is of great importance for their characterization and the extraction of (astro-)physical results.

Calibrating a gravitational-wave detector requires moving its test masses (measurement mirrors) by minute amounts. This motion must be known to high precision.

One possibility is to use an ancillary laser reflected off the mirrors. The laser’s photon radiation pressure will push the suspended mirrors with a known force, which in turn can be converted into a mirror displacement. Relating the mirror displacement to the interferometer output then enables the calibration of the instrument.

Photon-pressure calibration can be used together with electrostatic actuation of the mirrors to validate the absolute calibration and monitor its long-term stability.

Relevant publications

Mossavi, K.; Hewitson, M.; Hild, S.; Seifert, F.; Weiland, U.; Smith, J. R.; Lück, H.; Grote, H.; Willke, B.; Danzmann, K.: A photon pressure calibrator for the GEO 600 gravitational wave detector. Physics Letters A 353 (1), pp. 1 - 3 (2006)

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Photon-pressure calibration

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