Spectral optical vortex modulation from geometric phase diamond metasurface arrays

Abstract

Agile management of the optical orbital angular momentum encompasses temporal, spatial, and spectral aspects that, once combined, offer new perspectives in our way to manipulate light. To date the spectral control is mainly limited to tunable operating wavelength and polychromatic capabilities. Recently, a multispectral approach has been proposed [Phys. Rev. Lett. 121, 213901 (2018)] to achieve independent orbital angular momentum state control on multiple spectral channels. Here we report on the design, fabrication and implementation of a solid-state multispectral approach that consists of arrays of optical diamond micro-metasurfaces. Obtained device exhibits superior performances with respect to the original attempt, both regarding the spectral vortex purity, the ability to deal with high photon flux, and the orbital angular momentum diversity across the spectrum. These results motivate further development of metasurface-based integrated spin-orbit photonics technologies.

Spin‐Orbit Modal Optical Vortex Beam Shaping from Dielectric Metasurfaces

“…An example of it can be found in the context of nonmodal optical vortex generation using dielectric metasurfaces having a discrete design of an azimuthal nature. [ 20 ] Finally, the item (iv) is expected to induce substantial reflection losses when using materials with high refractive index as is the case here, see Figure S1d (Supporting Information). A subtler effect from Fresnel reflection is related to the optical anisotropy of the metasurface which brings an additional space‐variant modification of the polarization state of the light field that propagates through the material, which is not compensated by design in the present work.…”

Polarimeter for Detection of Anisotropy from Reflectance

“…(b) SEM images of the q-plate showing period Λ = 250 nm and 100 nm width of the diamond grating ridges; poly-crystalline diamond membrane of 3 µm thickness was Cr-coated, mask-patterned by EBL, developed and plasma etched (see processing details in ref. [22]). (c) The δ, α and ψ, χ dependencies from four segments in sequence measured in reflection using polarimeter.…”

“…The optical slow-axis follows azimuth angle θ as β = qθ with N = 12 segments (π/4 difference of a grating orientation between the neighboring regions). (b) SEM images of the q-plate showing period Λ = 250 nm and 100 nm width of the diamond grating ridges; poly-crystalline diamond membrane of 3 µm thickness was Cr-coated, mask-patterned by EBL, developed and plasma etched (see processing details in ref [22]…”

Polarimeters for the Detection of Anisotropy from Reflectance

“…( b ) SEM images of the q-plate showing period nm and with a 100 nm width of the diamond grating ridges; the poly-crystalline diamond membrane of m thickness was Cr-coated, mask-patterned via EBL, developed and plasma etched (see processing details in ref. [ 25 ]). ( c ) The and dependencies from four segments in sequence measured in reflection using a polarimeter.…”

“…The optical slow-axis follows azimuth angle θ as β = qθ with N = 12 segments (π/4 difference in the grating orientation between the neighboring regions). (b) SEM images of the q-plate showing period Λ = 250 nm and with a 100 nm width of the diamond grating ridges; the poly-crystalline diamond membrane of 3 µm thickness was Cr-coated, mask-patterned via EBL, developed and plasma etched (see processing details in ref [25]…”