Beam metrology and control for the Nulling Interferometry Cryogenic Experiment

Thomas Birbacher; Adrian M. Glauser; Mohanakrishna Ranganathan; Jonah T. Hansen; Suvrath Mahadevan; Sascha P. Quanz

doi:10.1117/12.3018652

28 August 2024 Beam metrology and control for the Nulling Interferometry Cryogenic Experiment

Thomas Birbacher, Adrian M. Glauser, Mohanakrishna Ranganathan, Jonah T. Hansen, Suvrath Mahadevan, Sascha P. Quanz

Proceedings Volume 13095, Optical and Infrared Interferometry and Imaging IX; 1309538 (2024) https://doi.org/10.1117/12.3018652
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Conference Poster

Abstract

We present our progress in stabilising the warm precursor of the Nulling Interferometry Cryogenic Experiment (NICE), a laboratory testbed demonstrating key mid-infrared nulling technologies for the Large Interferometer for Exoplanets (LIFE). To fulfil the preliminary requirements of NICE, the optical path length difference (OPD) between the beams has to be controlled to within 0.8nm RMS, while beam pointing and shear have to be controlled to within ≈1μm and ≈1μrad RMS, respectively. A heterodyne laser metrology system was implemented to monitor OPD and shear in NICE, with pointing measurements following soon. The metrology beams follow the science beams with minimal non-common paths, and modulation techniques enable simultaneous measurements of all critical paths through the testbed at 1kHz analog bandwidth. We use quadrant photodiodes and a small number of components in a compact layout, simplifying future cryogenic or space-based implementations. The noise of the metrology measured in a mock-up is < 0.8nm RMS in OPD, and < 85nm RMS in beam position, with crosstalk between the beams lower than the sensor noise, despite performing multiple measurements on the same detector with overlapping metrology beams. In the warm precursor of NICE, we achieve closed-loop OPD control to within 14nm RMS, which enables an improvement in null depth and stability by a factor of ≈10, reaching a 2 ⋅ 10⁻⁴ average null over a two-minute period. The metrology and control systems thus provide both an accurate diagnostic and characterisation tool for NICE, as well as a means to achieve deeper and more stable nulls. The main limitation is a 48Hz vibration from mechanical resonances in the setup, which we will mitigate with an improved mechanical design.

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Thomas Birbacher, Adrian M. Glauser, Mohanakrishna Ranganathan, Jonah T. Hansen, Suvrath Mahadevan, and Sascha P. Quanz "Beam metrology and control for the Nulling Interferometry Cryogenic Experiment", Proc. SPIE 13095, Optical and Infrared Interferometry and Imaging IX, 1309538 (28 August 2024); https://doi.org/10.1117/12.3018652

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available