Abstract
Intensity and polarization are two fundamental components of light. Independent control of them is of tremendous interest in many applications. In this paper, we propose a general vectorial encryption method, which enables arbitrary far-field light distribution with the local polarization, including orientations and ellipticities, decoupling intensity from polarization across a broad bandwidth using geometric phase metasurfaces. By revamping the well-known iterative Fourier transform algorithm, we propose “à la carte” design of far-field intensity and polarization distribution with vectorial Fourier metasurfaces. A series of non-conventional vectorial field distribution, mimicking cylindrical vector beams in the sense that they share the same intensity profile but with different polarization distribution and a speckled phase distribution, is demonstrated. Vectorial Fourier optical metasurfaces may enable important applications in the area of complex light beam generation, secure optical data storage, steganography and optical communications.
Highlights
Intensity and polarization are two fundamental components of light
Many other efforts of optical encoding have been made by using multiplexing meta-hologram that can encode the optical information into multi-channels of holographic images[26,27,28,29,30]
With respect to previously proposed methods, our approach defines the metasurface capability by considering the polarization distribution in the far field only, i.e., as a result of the propagation leading to left circular polarizations (CPs) (LCP) and right CP (RCP) far fields
Summary
Intensity and polarization are two fundamental components of light. Independent control of them is of tremendous interest in many applications. We propose a general vectorial encryption method, which enables arbitrary far-field light distribution with the local polarization, including orientations and ellipticities, decoupling intensity from polarization across a broad bandwidth using geometric phase metasurfaces. We propose a vectorial Fourier metasurface for which amplitude and polarization information can be addressed independently one from the other We utilize this specificity to encode intensity and two polarization information channels, namely ellipticity and azimuth, to produce far-field decoupled images. As a proof of principle, we designed a series of far-field intensity profiles presenting a given donut-like intensity distribution structured with different polarization orientations These vectorial fields look like the well-known cylindrical vector beams (CVBs; previously discussed in the literature). To resolve the encoded information, we use both conventional Stokes parameter measurements and vectorial ptychography to characterize both metasurface and their far-field complex amplitudes
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