Lens-free compound eye cameras based on angle-sensitive meta-surfaces
A lens-free ultrathin imaging sensor using a compound-eye vision modality can be formed by forming a metasurface on each pixel of an array of pixels in a solid state imaging sensor. The metasurface can be configured to form a diffraction grating that directs light incident on the metasurface at a predefined angle to excite surface plasmon polaritons into the solid state imaging sensor and light incident at any other angle is reflected or diffracted away from the metasurface. Each pixel of the imaging sensor can be configured using the metasurface to only receive light incident from a different portion of a field of view. A computational imaging system can be used to construct the image from the individual pixels.
1. An imaging sensor comprising:
at least one pixel sensor configured to produce an electrical signal in response to an optical signal received at a first surface of the single pixel sensor;
a metal film layer disposed over at least a portion of the first surface, the metal film including a top surface and a bottom surface;
a first dielectric layer disposed between the first surface and the bottom surface of metal film layer and a second dielectric layer disposed over at least a portion of the top surface of the metal film layer;
a periodic array of nanoparticles disposed on the second dielectric layer, the periodic array of nanoparticle being arranged in a predefined configuration such that light incident on the array of nanoparticles within a predefined range of angles with respect to periodic array of nanoparticles is diffracted by the array of nanoparticles into surface plasmon polaritons that propagate along the top surface of the metal film and become absorbed by the first surface and cause the at least one pixel sensor to produce an electrical signal; and
light incident on the array of nanoparticles that is not within the predefined range of angles is not diffracted into surface plasmon polaritons that propagate along the top surface of the metal film.
2. The imaging sensor according to claim 1 wherein the at least one pixel sensor includes a Germanium photoconductor.
3. The imaging sensor according to claim 1 wherein the metal film layer includes silver or gold.
4. The imaging sensor according to claim 1 wherein the metal film layer has a predefined thickness in the range from 10 nm to 1000 nm.
5. The imaging sensor according to claim 1 wherein the first dielectric layer includes silicon dioxide.
6. The imaging sensor according to claim 1 wherein the first dielectric layer has a predefined thickness in the range from 10 nm to 1000 nm.
7. The imaging sensor according to claim 1 wherein the second dielectric layer includes silicon dioxide.
8. The imaging sensor according to claim 1 wherein the second dielectric layer has a predefined thickness in the range from 10 nm to 1000 nm.
9. The imaging sensor according to claim 1 wherein the array of nanoparticles forms a diffraction grating comprising a unit cell including two or more rectangular nanoparticles separated by a predefined distance in a range from 10 nm to 100 nm.
10. The imaging sensor according to claim 9 wherein the diffraction grating includes at least two unit cells separated by a period, Λ, in a range from 250 nm to 2000 nm.
11. An imaging sensor comprising:
an array of pixel sensors forming a solid state photo detector material having a first surface configured to receive surface plasmon polaritons; and
a metasurface coupled to the first surface of the solid state photo detector material, the metasurface comprising:
a metal film layer disposed over at least a portion of the first surface, the metal film including a top surface and a bottom surface;
a first dielectric layer disposed between the first surface and the bottom surface of metal film layer and a second dielectric layer disposed over at least a portion of the top surface of the metal film layer; and
an array of nanoparticles arranged on the second dielectric layer forming a grating coupler section and a slits section.
12. The imaging sensor according to claim 11 wherein
the grating coupler section comprises a periodic array of nanoparticles arranged in a predefined configuration such that light incident on the array of nanoparticles within a predefined range of angles with respect to periodic array of nanoparticles is diffracted by the array of nanoparticles into surface plasmon polaritons that propagate along the top surface of the metal film layer; and
wherein the slits section positioned on a first side of the grating coupler section comprising a plurality of slits extending through the second dielectric layer, the metal film layer and the first dielectric layer to the solid state photo detector material such that the surface plasmon polaritons propagating along the top surface of the metal film layer propagate into the solid state photo detector material.
13. The image sensor according to claim 12 wherein the metasurface further includes a reflector section positioned on a side opposite to the first side and the reflector section further includes a grating of nanoparticles configured to reflect the surface plasmon polaritons away from the reflector section.
14. The image sensor according to claim 13 wherein the reflector section reflects the surface plasmon polariton toward the slits section.
15. The image sensor according to claim 13 wherein the reflector section reflects the surface plasmon polariton away from the solid state photo detector material.