Polarization spectroscopy of an excited state transition in Rubidium

We investigate polarization spectroscopy of an excited state transition in room temperature rubidium vapor. By applying a circularly polarized coupling beam, resonant with the 5(2)S(1/2) -> 5(2)P(3/2) transition, we induce anisotropy in the atomic medium that is then probed by scanning a probe beam across the 5(2)P(3/2) -> 6(2)S(1/2) transition. By performing polarimetry on the probe beam, a dispersive spectral feature is observed. We characterize the excited-state polarization spectrum as a function of coupling intensity for both isotopes and find that at high intensities, Autler-Townes splitting results in a sub-feature, which theoretical modelling shows is enhanced by Doppler averaging. This spectroscopic technique produces a narrow dispersive signal which is ideal for laser frequency stabilization to excited-state transitions. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.