Faraday rotation assisted by linearly polarized light

We demonstrate a type of chiral effect of an atomic medium. Polarization rotation of a probe beam is observed only when both a magnetic field and a linearly polarized coupling beam are present. We compare it with other chiral effects like optical activity, the Faraday effect, and the optically induced Faraday effect from the viewpoint of spatial inversion and time reversal transformations. As a theoretical model we consider a five-level configuration involving the cesium $D2$ transition. We use spin-polarized cold cesium atoms trapped in a magneto-optical trap to measure the polarization rotation versus probe detuning. The result shows reasonable agreement with a calculation from the master equation of the five-level configuration.

Figure 1

Five-level configuration for the light-assisted Faraday effect. Dotted lines near the $\mid l_{\pm }⟩$ states show Zeeman shifts, and dashed lines near the $\mid u_{\pm }⟩$ states show dressed states with Autler-Townes splittings.

Figure 2

(Color online) Schematic diagram of the experimental apparatus. ML: master laser. CL: coupling laser. PL: probe laser. OPLL: optical phase-lock loop. PD: fast photodiode. AOM: acousto-optic modulator. SE: solid étalon. WP: waveplate. PBS: polarizing beam splitter. INT: gated integrators. DAQ: data acquisition system. Inset shows the field configuration in the $xz$ plane.

Figure 3

(a) Normalized transmitted probe beam powers for the $+45°$ (▴ or ∎) and $-45°$ (▵ or ◻) components for ($B$ only or coupling only) case. (b) $+45°$ (●) and $+45°$ (엯) components with both $B$ and coupling fields. (c) Parallel (▴, ∎, ●) and perpendicular (▵, ◻, 엯) components for ($B$ only, coupling only, with both) cases. (d) ${\sigma }^{+}$ (●) and ${\sigma }^{-}$ (엯) components with both $B$ and coupling fields. Solid lines are theory curves.

Figure 4

Rotation angle in degrees for all three cases: with $B$ only (◻), with coupling only (▵), and with both $B$ and coupling fields (●). Solid and dotted lines are theory curves.

Figure 5

(Color online) Normalized Zeeman shift of the $\mid 6P_{3∕2},F^{\prime }=3,m_F⟩$ states.