Optically transparent radio frequency reflectarray devices for beam redirection and broadening
The present disclosure provides optically transparent reflectarrays, and methods of constructing and using such reflectarrays.
1 . A passive reflectarray comprising:
an optically transparent substrate that has a thickness in a range from 0.3 millimeters to 1.0 millimeters;
a metasurface comprising a two-dimensional array of a plurality of resonant patches disposed over the optically transparent substrate, each resonant patch comprising a substantially planar first optically transparent conductor, wherein the first optically transparent conductor has a sheet resistance of less than ten ohms per square and comprises a mesh of microwires, wherein the microwires of the resonant patches have a maximum line width that is less than eight microns, wherein the size of each of the resonant patches is in a size range of from 0.1 millimeters square to 3.5 millimeters square, wherein a first resonant patch of the plurality of resonant patches has a major surface area of a first size, and wherein a second resonant patch of the plurality of resonant patches has a major surface area of a second size; and
an optically transparent ground plane comprising a second optically transparent conductor disposed under the optically transparent substrate, wherein the second optically transparent conductor is substantially planar and has a sheet resistance of less than ten ohms per square and comprises a mesh of microwires, wherein the microwires of the optically transparent ground plane have a maximum line width that is less than eight microns,
wherein the passive reflectarray has an optical transmittance that is eighty percent or more in a visible wavelength band from 380 nanometers to 780 nanometers.
2 . The passive reflectarray of claim 1 , further comprising a reflection profile configured to be a beam deflector and to implement an Echelle grating having an aperture size of about 3λ 0 to about 30λ 0 and a blazing angle of about 1° to about 40°, λ 0 being a wavelength of an RF wave in free-space corresponding to a design frequency of the metasurface.
3 . The passive reflectarray of claim 1 , wherein the metasurface comprises a linear phase gradient.
4 . The passive reflectarray of claim 1 , wherein at least one resonant patch of the array of resonant patches is ring-shaped, square, rectangular, or circular shaped.
5 . The passive reflectarray of claim 1 , wherein an RF wave produced by the reflectarray has a frequency ranging from about 5 GHz to about 30 GHz.
6 . The passive reflectarray of claim 1 , wherein the optically transparent substrate comprises glass or a polymer.
7 . The passive reflectarray of claim 1 , wherein the metasurface comprises silver (Ag), indium tin oxide (ITO), or nanoparticle-doped silica.
8 . The passive reflectarray of claim 1 , wherein the metasurface comprises nanowire meshes made by one of electrospun fiber templates, crack lithography, or spinning layers of metallic nanowires.