Atomic thermometry with modulation transfer spectroscopy of potassium D1 and D2 transitions

We report on temperature study of modulation transfer spectroscopy of the 4S1/2→4P1/2 (D1) and 4S1/2→4P3/2 (D2) transition of naturally abundant potassium in a vapor cell. This transition is critical for laser cooling and optical pumping of potassium and for robust laser frequency stabilization. However, no prior work has explored their use as atomic thermometers. Our study is, therefore, motivated us to consider D1 and D2 transitions as a atomic thermometry. Interestingly, despite the absence of a closed transition, the small ground-state hyperfine splitting in potassium results in strong crossover features in the D1 modulation transfer spectrum. To emphasize this, we compare the temperature dependency of D1 and D2 spectra of potassium. Further, we compare our experimental results of different pump–probe polarization configurations to identify the optimal signals for modulation transfer spectrum. We find nice zero crossing for different polarization configurations and compare the sensitivity.