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We report the observation of enhanced magneto-optic rotation as the coherent superposition of different hyperfine states is established in an atomic sample. The polarization rotation near the two-photon Raman resonance condition appears to have an analogous characteristic to the well established Faraday rotation observed in the vicinity of a single-photon resonance; however, it contains sharp features arising from coherent population trapping states. The profile of the two-photon rotation signal exhibits interesting features for a slightly imbalanced circular polarization component of the laser field as well as for on and away from the single-photon resonance. The investigation can be used to explore the effect of superposition states generated by coherent population trapping on optical activity. A complete density matrix based numerical simulation that consistently captures all the relevant features of the experiment is presented. The experimental and theoretical investigation can be useful for magnetometry using polarization rotation near two-photon Raman resonance.

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We propose resilient quantum superposition states in closed-loop multilevel system which result in myriad quantum interference phenomena. An interplay of these superposition states results in a whole gamut of atomic phenomena including coherent population trapping (CPT), electromagnetically induced transparency (EIT), electromagnetically induced absorption (EIA), amplification without inversion (AWI) and enhancement of refractive index accompanied with negligible absorption. The polarization and the phases of the fields transform the underlying superposition of the excited states leading to all these effects, where, given the macroscopic nature of these phenomena the quantum superposition states as well as the synergy between them can be ascertained. Numerical simulations for D1 transition in room temperature Rb⁸⁷ atomic vapour system bear out these findings.