Picometer and nanoradian optical heterodyne interferometry for translation and tilt metrology of the LISA gravitational reference sensor

Abstract

The Laser Interferometer Space Antenna (LISA) aims at detecting gravitational waves by referencing heterodyne interferometry to free-flying (inertial) proof masses, located at the corners of a triangle with 5 million kilometers arm length. The position of each proof mass with respect to the associated satellite must be measured with 1 pm Hz −1/2 -sensitivity in translation measurement and below 10 nrad Hz −1/2 -sensitivity in attitude. In this paper, we present a compact heterodyne interferometer utilizing polarizing optics combined with the method of differential wavefront sensing (DWS) serving as a demonstrator for a complete optical readout system of the proof mass translation and attitude aboard the LISA satellites. Our interferometer is based on a highly symmetric design, where reference and measurement beam have similar optical paths and equal polarization and frequency. Intensity stabilization of the laser radiation, phaselock of the laser frequencies at the fiber outputs and a digital phase measurement based on a field programmable gate array (FPGA) are implemented to achieve noise levels below 10 pm Hz −1/2 and 10 nrad Hz −1/2 , respectively, for frequencies >10 −2 Hz.

A high-performance iodine-based frequency reference for space applications

“…Using this AI technology, a heterodyne interferometer was developed at Astrium (Friedrichshafen) in a collaboration with the Humboldt-University Berlin and the University of Applied Sciences Konstanz [18], [19], [20]. This setup is realized as a demonstrator for the optical readout of the LISA gravitational reference sensor.…”

Dimensional stability validation and sensor calibration with sub-nanometer accuracy

“…Non-contact optical heterodyne, homodyne and phase shifting interferometry minimize the perturbation on the sample under test and provide high sensitivity, that scales with the optical wavelength [3][4][5][6]. Versatile configurations and large displacement range are supported.…”

Relative optical wavefront measurement in displacement measuring interferometer systems with sub-nm precision

“…Laser interferometry is applied for a wide range of measurement applications in the fields of high precision position sensing: measuring displacements of precision stages [1,2], gravitational wave detection in the LIGO [3] and LISA [4,5] projects, atomic force microscopy [6] and measuring orbital angular momentum of photons [7]. It is also often used for calibration of other measurement tools [8] such as capacitive sensors, inductive sensors, and optical encoders.…”