Practical wavelength calibration considerations for UV-visible Fourier-transform spectroscopy

Area of Science:

• Optical Physics
• Metrology
• Spectroscopy

Background:

• Modern laser-controlled Michelson interferometers possess an intrinsic wavelength scale, known as the Connes advantage, enabling high wavelength accuracy.
• Achieving a relative uncertainty of 10^-8 in line position is feasible with single-point calibration.
• Practical limitations such as finite aperture and imperfect alignment necessitate wavelength scale corrections.

Purpose of the Study:

• To discuss practical aspects of accurate interferometer calibration in the UV-visible region.
• To address critical issues in using external wavelength standards.
• To evaluate and select appropriate wavelength standards for calibration.

Main Methods:

• Utilizing a laser-controlled Michelson interferometer for wavelength calibration.
• Employing single-point, multiplicative calibration techniques.
• Investigating calibration using external wavelength standards and Fabry-Perot interferometry.

Main Results:

• Demonstrated the potential for superb wavelength accuracy (relative uncertainty ~10^-8) with proper calibration.
• Identified finite aperture and geometric misalignment as key factors requiring correction.
• Observed anomalous results for Ar II and (198)Hg I when used as wavelength standards via Fabry-Perot interferometry.

Conclusions:

• Accurate calibration is essential for realizing the full potential of Michelson interferometers for precise wavelength measurements.
• Careful selection and validation of external wavelength standards are critical for reliable calibration.
• Further investigation is needed to understand the anomalous behavior of certain potential wavelength standards.