Characterization of nonlinear spectral linewidth and light shift in diffuse laser-cooled atoms

We demonstrate an integrating sphere to cool ⁸⁷Rb atoms and measure the recoil-induced resonance and electromagnetically induced absorption spectrum. We measure the relationship between their linewidth and light shift with variation of the detuning and power of the cooling laser and study the performance of the diffuse laser cooling mechanism by the absorption linewidth radio Δν_E/Δν_R and light shift |Δ_R–Δ_E| using nonlinear spectroscopy. Specifically, when Δν_E/Δν_R reaches a value of 1.57, the temperature and number of cold atoms achieve the optimal cooling effect. This characterization of absorption linewidth and light shift will provide a method to estimate whether diffuse light cooling achieves the best cooling effect, contributing to the future development of isotropic laser cooling for application in quantum sensing.