Power Dependent Lineshape Corrections for Quantitative Spectroscopy

TL;DR

This paper introduces power-dependent corrections to the Voigt profile used in spectroscopy, reducing saturation-induced errors in linewidth measurements at higher probe powers.

Contribution

It develops a simple atomic model to calculate and parametrize corrections to the Voigt profile, improving the accuracy of spectral line fitting under varying power conditions.

Findings

Correction terms significantly reduce power-dependent errors in linewidth fitting

Experimental validation confirms the effectiveness of the corrections

Numerical simulations support the proposed model

Abstract

The Voigt profile - a convolution of a Gaussian and a Lorentzian - accurately describes the absorption lines of atomic and molecular gases at low probe powers. Fitting such to experimental spectra yields both the Lorentzian natural linewidth and the Gaussian Doppler broadening. However, as the probe power increases saturation effects introduce spurious power dependence into the fitted Doppler width. Using a simple atomic model, we calculate power-dependent corrections to the Voigt profile, which are parametrized by the Gaussian Doppler width, the Lorentzian natural linewidth, and the optical depth. We show numerically and experimentally that including the correction term substantially reduces the spurious power dependence in the fitted Gaussian width.