Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Validation of optical pathlength stability in a LISA test-bench demonstrator

Shivani Harer, Maxime Vincent, Hubert Halloin, Ouali Acef, Nisrine Arab, Romain Arguel, Axel Arhancet, Damien Bachet, Nathalie Besson, Sébastien Bize, Aurélien Boutin, Sara Bruhier, Christelle Buy, Michael Carle, Jean-Pierre Coulon, Nicoleta Dinu-Jaeger, Mathieu Dupont, Christophe Fabron, R'emi Granelli, David Holleville, Dominique Huet, Pascal Huguet Chantôme, Eric Kajfasz, Mickael Lacroix, Matthieu Laporte, Rodolphe Le Targat, Jean Lesrel, Michel Lintz, Michel Lours, Christophe Meessen, Mourad Merzougui, Alexis Mehlman, Marco Nardello, Laure Oudda, Benjamin Pointard, Pierre Prat, Emmanuelle Rivière, Jérôme Royon, Aurélia Secroun, Samuel Sube, Johannes Veyron, Thomas Zerguerras, Julien Zoubian

TL;DR

This work addresses achieving picometer-level optical pathlength stability for LISA's long-baseline interferometry by validating a Zerodur-based optical bench (ZIFO) in a vacuum testbed. It combines dual Nd:YAG lasers, balanced detection, phasemeter channels with pilot-tone jitter correction, and a PCA-based noise reduction approach to characterize and mitigate dominant noise sources, including tilt-to-length coupling and thermoelastic effects. The study demonstrates $10~\mathrm{pm}/\sqrt{\mathrm{Hz}}$ stability over $1~\mathrm{mHz}$–$1~\mathrm{Hz}$ under Run A, identifies common-mode pilot-tone noise as a key challenge, and shows that correlated-noise subtraction can reduce non-common-mode noise in some runs. These results validate the metrology concepts for the LISA interferometric core and help guide the next phase of industrial integration and further environmental control for future missions.

Abstract

The Laser Interferometer Space Antenna (LISA) observatory is a future L3 mission of the European Space Agency (ESA) to detect gravitational waves, set to launch in 2035. The detector constellation will conduct interferometry to picometer stability over an unprecedented arm length of 2.5 million km. In this paper, we present the development and testing results for the Zerodur interferometer (ZIFO), an optical demonstrator built to validate critical technology for the test setup of the interferometric core of LISA. Optical path length stability measurements on the ZIFO demonstrate successful reduction of bench noise to maintain the 10 pm/$\sqrt{\text{Hz}}$ specification across the 1 mHz to 1 Hz frequency band. We also identify and characterize dominant noise sources from phasemeters and correlations of beam tilt into the path length that were observed during the test campaign.

Validation of optical pathlength stability in a LISA test-bench demonstrator

TL;DR

This work addresses achieving picometer-level optical pathlength stability for LISA's long-baseline interferometry by validating a Zerodur-based optical bench (ZIFO) in a vacuum testbed. It combines dual Nd:YAG lasers, balanced detection, phasemeter channels with pilot-tone jitter correction, and a PCA-based noise reduction approach to characterize and mitigate dominant noise sources, including tilt-to-length coupling and thermoelastic effects. The study demonstrates stability over – under Run A, identifies common-mode pilot-tone noise as a key challenge, and shows that correlated-noise subtraction can reduce non-common-mode noise in some runs. These results validate the metrology concepts for the LISA interferometric core and help guide the next phase of industrial integration and further environmental control for future missions.

Abstract

The Laser Interferometer Space Antenna (LISA) observatory is a future L3 mission of the European Space Agency (ESA) to detect gravitational waves, set to launch in 2035. The detector constellation will conduct interferometry to picometer stability over an unprecedented arm length of 2.5 million km. In this paper, we present the development and testing results for the Zerodur interferometer (ZIFO), an optical demonstrator built to validate critical technology for the test setup of the interferometric core of LISA. Optical path length stability measurements on the ZIFO demonstrate successful reduction of bench noise to maintain the 10 pm/ specification across the 1 mHz to 1 Hz frequency band. We also identify and characterize dominant noise sources from phasemeters and correlations of beam tilt into the path length that were observed during the test campaign.

Paper Structure

This paper contains 17 sections, 22 equations, 12 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Instrument architecture
  3. Data acquisition and processing
  4. Measurement performance and noise assessment
  5. Pathlength Stability
  6. Noisy
  7. Removal of Correlated Noise
  8. Test set up temperature stability
  9. Test environment
  10. Conclusion
  11. Performance Model
  12. Instrumental Noise:
  13. Thermoelastic Noise:
  14. Vibration Noise:
  15. Tilt-to-length Noise:
  16. ...and 2 more sections

Figures (12)

  • Figure 1: Zerodur Optical Bench placed in its thermal shield in the ERIOS vacuum tank
  • Figure 2: Schematic representation of the interferometry bench and entire test set-up along with corresponding partner.
  • Figure 3: Thermoelastic and interferometer noise models for IFO$_1$ (left) and IFO$_{2/1}$ (right) differential interferometer measurement. Phase noise in interferometers during Run A is overlaid to enable comparison between model and measurement. The 10 reference accounts for a relaxation factor of ${1}/{f^2}$ below 3, as is LISA, the noise floor below this frequency is determined by test-mass acceleration noise LISA:2024hlh and not optical metrology noise.
  • Figure 7: Coherence between the phase in IFO$_{2/1}$ and the first principal component for Run C, the high coherence region marked by the dashed rectangle.
  • Figure 9: The amplitude spectral density of the temperature measurement for Run C for different temperature sensors inside the photo-receivers, on the thermal shield and on the vacuum tank.
  • ...and 7 more figures