Thermal Alkali Vapour Spectroscopy: Buffer Gas Enhanced K Systems and Magneto-Optical Rb Applications

Abstract

We present experimental and theoretical work on atomic bandpass filters and spectroscopic characterisations of alkali vapour systems for magneto-optical applications. We demonstrate a new method for generating arbitrary angle magnetic fields in atomic filters using Rb vapour. This involves a fixed of per- manent magnets in a Voigt geometry combined with a solenoid. We compare this method with the previously used method of rotating the permanent mag- net pair. This setup offers more precise and flexible angle control. While both methods generate similar transmission profiles, the new setup allows larger an- gles and supports longer vapour cells, enhancing magneto-optical filters. Next, we investigate K D1 transition in the presence of neon buffer gas, in partic- ular the pressure induced broadening and frequency shift, and the Zeeman splitting in the hyperfine Paschen-Back (HPB) regime. We use dual-control temperature systems to independently adjust Doppler and collisional effects, and we achieve excellent agreement with literature values for potassium-neon collisions. For the first time, buffer gas effects integrate into our theoretical model ElecSus, producing accurate prediction of modified Voigt profiles. We conduct a comprehensive experimental and theoretical study into the Stokes polarimetry of potassium atomic vapour with neon buffer gas, focusing on the temperature and magnetic field effects. This work represents the first appli- cation of ElecSus to model the buffer gas polarimetry of K D1 transitions. This study provides new insights into the effects of buffer gases on Stokes pa- rameters, and indicates advances in a theoretical framework for understanding atom-light interactions in buffer gas environments.