Accurate measurement of interferometer group delay using field-compensated scanning white light interferometer

Area of Science:

• Optics and Photonics
• Astronomy and Astrophysics

Background:

• Accurate calibration of group delay in interferometers is crucial for high-precision radial velocity (RV) measurements in astronomy.
• Existing methods face challenges with low spatial coherence light sources and require frequent recalibration.

Purpose of the Study:

• To introduce a novel field-compensated white light scanning Michelson interferometer for accurate interferometer calibration.
• To enable precise group delay measurements essential for advanced astronomical observations.

Main Methods:

• Utilized a field-compensated Michelson interferometer with a translating compensation prism for optical path difference (OPD) scanning.
• Employed a multimode fiber-coupled LED (500-560 nm) as a low spatial coherence light source, ensuring phase coherence over large scanning ranges.
• Implemented dual-laser wavelength references and an iodine absorption spectrum for achromatic OPD scanning calibration and cross-verification.

Main Results:

• Achieved high optical efficiency for improved interferogram signal-to-noise ratio.
• Determined group delay with an accuracy of 1×10⁻⁵.
• Attained phase angle precision typically of 2.5×10⁻⁶ over a wide wavelength range.

Conclusions:

• The novel interferometer provides a robust and accurate calibration tool for RV experiments.
• The developed methods ensure reliable and precise group delay measurements, advancing astronomical observation capabilities.