Abstract
Spin orbit interaction and the resulting Spin Hall effect of light are under recent intensive investigations because of their fundamental nature and potential applications. Here, we report an interesting manifestation of spin Hall effect of light and demonstrate its tunability in an inhomogeneous anisotropic medium exhibiting spatially varying retardance level. In our system, the beam shift occurs only for one circular polarization mode keeping the other orthogonal mode unaffected, which is shown to arise due to the combined spatial gradients of the geometric phase and the dynamical phase of light. The constituent two orthogonal circular polarization modes of an input linearly polarized light evolve in different trajectories, eventually manifesting as a large and tunable spin separation. The spin dependent beam shift and the demonstrated principle of simultaneously tailoring space-varying geometric and dynamical phase of light for achieving its tunability (of both magnitude and direction), may provide an attractive route towards development of spin-optical devices.
Highlights
Spin orbit interaction and the resulting Spin Hall effect of light are under recent intensive investigations because of their fundamental nature and potential applications
In a simple yet elegant system of a twisted nematic liquid crystal-based spatial light modulator (SLM), we demonstrate that one can simultaneously generate desirable spatial gradients of both the geometric and the dynamical phases of light to produce such spin dependent beam shift in a regulated fashion
The effect is eventually manifested as a spin-dependent splitting of input linearly polarized beam, where the constituent two orthogonal circular polarization modes evolve in different trajectories leading to a large and tunable spin separation
Summary
Tunable Spin Specific Beam Shift in inhomogeneous anisotropic medium. The inhomogeneous anisotropic medium was realized by modulating the pixels of a twisted nematic liquid crystal-based SLM by user controlled grey level (n) distributions (see Methods). The grey level dependence of total phase experienced by RCP state Φ+tot(n) (shown using color bar) and the noted phase gradients are based on determination of geometric and dynamical phases, results of which are presented subsequently. Equal to d ψeff (n) δtot(n)) anddnthe for the SLM It corresponding should be estimates dn noted that the determined polarization parameters (δeff(n), ψ eff(n) and for the dynamical and the PB geometric phases are subject to small. Comparison of the experimental momentum domain beam shifts for the input RCP state and the corresponding theoretical predictions (using the results of Fig. 3c in eq 5) shows reasonable agreement (Fig. 3d). An approximated linear dependence of Φ+tot(n) with n (for n ≈ 30–170 in Fig. 3c) was assumed and the spatial dimensions (over which the grey levels were applied) were duly considered (the values of the spatial gradients dΦ+tot(x) noted in Fig. 2 are based on this approximation)
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