Experimental and theoretical characterisation of Stokes polarimetry of the potassium D1 line with neon buffer gas broadening

Abstract: This study presents a comprehensive experimental and theoretical characterisation of Stokes polarimetry in potassium (K) vapour on the D1 line. Measurements were performed in the weak-probe regime, investigating the influence of neon buffer gas in the presence of an applied magnetic field in the Faraday geometry. While previous Stokes polarimetry studies in alkali-metal vapours have been conducted, the specific effects of buffer gas-induced broadening and shifts on the observed Stokes parameters remained largely underexplored. Here, experimental measurements of absolute absorption and dispersion were compared with a theoretical model for the electric susceptibility of the vapour, calculated using the established software package $ElecSus$. This work marks the first application of $ElecSus$ to model buffer gas polarimetry of the potassium D1 line, with validation performed against experimental spectra for magnetic fields up to 1.2 kG. Our findings provide new insight into how the presence of buffer gas influences the observed Stokes parameters, thereby enhancing the predictive capabilities of theoretical frameworks for atom-light interactions in buffer-gas environments.