Electromagnetically induced transparency in Rydberg hot atoms using polarization spectroscopy and Laguerre-Gaussian laser modes

In this work, electromagnetically induced transparency (EIT) is investigated in a three-level ladder of rubidium atoms at room temperature using a Rydberg state and a Laguerre-Gaussian mode laser. The probe field, which is Gaussian, couples the 5S_1/2 → 5P_3/2 states. The control field, which can be in either Gaussian or Laguerre-Gaussian (LG) modes, couples the 5P_3/2 → nD states, with n = 42. The EIT spectrum is measured through polarization spectroscopy (PS), resulting in a dispersive signal. The dispersive EIT linewidth is narrower for the LG mode than for a Gaussian mode, which is due to the spatial distribution of the LG profile. We have implemented a probe transmission model using a simplified Lindblad master equation, which reproduces well the experimental results. The use of the PS signal eliminates the need to fit a curve when measuring EIT linewidths while still providing subnatural widths.