pISSN 0374-4914 eISSN 2289-0041

## Research Paper

New Phys.: Sae Mulli 2019; 69: 667-672

Published online June 28, 2019 https://doi.org/10.3938/NPSM.69.667

## Dependence of Polarization Spectroscopy on Pump Beam Intensity for the $^\text{87}\text{Rb}$ ${F_g=2\rightarrow F_e=3}$ Transition

Geol MOON*, Hyun-Jong KANG, Heung-Ryoul NOH

Department of Physics, Chonnam National University, Gwangju 61186, Korea

Correspondence to:cnuapi@jnu.ac.kr

Received: April 2, 2019; Revised: April 24, 2019; Accepted: May 3, 2019

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

### Abstract

We have investigated the dependence of polarization spectroscopy signal on the pump beam intensity around the $F_g=2 \rightarrow F_e=3$ resonance transition line of $^{87}$Rb and analyzed the amplitude, linewidth, and slope of the signal for pump beam intensities up to 60 $I_s$, where $I_s$ is the saturation intensity. As the pump beam intensity increases in the range smaller than $I_s$, the amplitude, linewidth, and slope of the signal increase linearly. On the other hand, as the pump beam intensity grows in the range much larger than $I_s$, the amplitude and slope are reduced, and the linewidth became saturated. The dependence of the polarization spectroscopy signal on the pump beam intensity is mostly caused by the redistribution of the populations in the $F_g=2,m_g$ Zeeman states with the growth of $\sigma^+$ pump beam intensity, and interestingly, we observe that the change of the atom number density in the vapor cell dramatically modifies the amplitude of the signal in the range much larger than the saturation intensity $I_s$. The observed experimental results can be interpreted well by using the analytical solution for the polarization spectroscopy signal.

Keywords: Polarization spectroscopy, Rubidium atom, Pump beam intensity