Saturation of the all-optical Kerr effect in solids

Zachary H. Levine

Rubidium vapor cells play a key role in contemporary quantum optics since they have strong nonlinear interactions with a low-power incident laser light. The simplest nonlinear interaction is the Kerr effect. Although most calculations concentrate on the unsaturated Kerr effect, the saturated Kerr effect has been measured in many materials including 85Rb and 87Rb vapor. Moreover, entanglement-generating vapor cells often operate in the saturated regime. Here, the calculation of the saturated Kerr effect for rubidium vapor at the D2 line uses a density matrix formulation that includes two hyperfine-split levels and all magnetic sublevels in each of the ground and excited states to account for incomplete optical pumping: the transit time of the atoms through the beam is too short to reach a final population distribution. The calculation shows a rapid qualitative change at low optical power, in semiquantitative agreement with experimental data.

George P. Miroshnichenko

Liang Hong, Yueping Niu, Li Deng +1 more

Zachary H. Levine, Ziran Du

The Kerr effect in atomic vapor may be regarded as the power saturation of the susceptibility. Hence the saturable Kerr effect is intimately tied to the standard Kerr effect. Here, we calculate the saturable Kerr effect without free parameters using a two-level system and find good agreement with experimental results. Our approach permits a direct comparison of theory to experiment without an extrapolation to low power as required by previous approaches. An experimentally observed asymmetry between red and blue detuning led us to consider a model with one ground state and three excited states. Such an asymmetry cannot be described by a two-state model. The model predicts about 25% of the observed asymmetry.

Baldassare Di Bartolo

Li Chun-Fei, Yuxiao Wang, Xueru Zhang

The intensity-dependent nonlinear refraction phenomena in a non-resonant multilevel molecular system is studied using rate equations in steady state, including saturable refraction, reverse saturable refraction, and the turnover between these two effects. The relationship between the refraction saturation and the optical Kerr effect is also discussed.