Polarization state generation with a metasurface
The present disclosure provides an optical component, which may be a metasurface grating, including (a) a substrate; and (b) an array of subwavelength-spaced phase-shifting elements, which are tessellated on the substrate to produce, when illuminated with a polarized incident light, a diffracted light beam with a distinct polarization state for each of a finite number of diffraction orders, wherein the finite number is 2 or more.
1. An optical component comprising
(a) a substrate; and
(b) an array of subwavelength-spaced phase-shifting elements, which are tessellated on the substrate configured to produce, when illuminated with a polarized incident light, a diffracted light beam with a distinct polarization state for each of a finite number of diffraction orders, wherein the finite number is 2 or more.
2. The optical component of claim 1 , wherein the array is a one-dimensional array.
3. The optical component of claim 1 , wherein the phase-shifting elements comprise pillars.
4. The optical component of claim 3 , wherein the pillars have a rectangular cross-section.
5. The optical component of claim 1 , wherein the phase-shifting elements comprise titanium dioxide, silicon nitride, an oxide, a nitride, a sulfide, or pure element.
6. The optical component of claim 1 , wherein the subwavelength-spaced phase-shifting elements are tessellated on the substrate and are configured to produce, when illuminated with the polarized incident light, four distinct polarization states.
7. The optical component of claim 6 , wherein the subwavelength-spaced phase-shifting elements are tessellated on the substrate and are configured to produce a +45° linear polarization state, a right circular polarization state, a left circular polarization state and a −45° linear polarization state at −2, −1, +1 and +2 diffraction orders, respectively, when illuminated with the incident light which is +45° linear polarized relative to a surface of the substrate.
8. The optical component of claim 6 , wherein the subwavelength-spaced phase-shifting elements are tessellated on the substrate and are configured to produce at −2, −1, +1 and +2 diffraction orders four polarization states corresponding to vertices of a tetrahedron inscribed in the Poincare sphere when illuminated with the incident light which is +45° linear polarized relative to a surface of the substrate.
9. The optical component of claim 1 , wherein each dimension of the substrate parallel to a surface of the substrate is no more than 2 millimeters (mm).
10. The optical component of claim 1 , wherein a number of the subwavelength-spaced phase-shifting elements is in a range from 10 to 40.
11. The optical component of claim 1 , wherein polarization states for each of the diffraction orders are linearly independent.
12. A optical instrument comprising:
(a) the optical component of claim 1 ; and
(b) one or more detecting elements, each configured to detect the diffracted light beam for one of the diffraction orders.
13. The optical instrument of claim 12 , comprising the finite number of the detecting elements.
14. The optical instrument of claim 12 , wherein the detecting elements comprise single-wave length detecting elements, multi-wavelength detecting elements, or imaging sensors.
15. The optical instrument of claim 14 , wherein the single-wave length detecting elements are linear in intensity at a wavelength of the incident light.
16. The optical instrument of claim 12 , wherein the optical instrument is a spectroscopic polarimeter, a polarization imaging instrument, or a polarimeter.
17. The optical instrument of claim 16 , wherein the polarimeter is configured to determine an unknown polarization in a test light, wherein an incident angle of the test light differs from a calibration incident angle of the optical component by ±5°.
18. The optical instrument of claim 12 , further comprising a first linear polarizer positioned on an optical path of an incident light towards the optical component.
19. The optical instrument claim 12 , which does not comprise a birefringent optical element, or which does not comprise a metasurface element other than the optical component.
20. The optical instrument of claim 12 , further comprising a second linear polarizer on an optical path of the diffracted beams towards the detecting elements.
21. The optical instrument of claim 20 , wherein an extinction ratio of the second linear polarizer is in a range from 500 to 200000.
22. The optical instrument of claim 12 , further comprising a lens positioned on an optical path of one or more of the diffracted beams towards the detecting elements.
23. A polarization testing method comprising:
illuminating the optical component of claim 1 with a test light; and
measuring a light intensity of a beam diffracted from the optical component for each of the finite number of the diffraction orders.
24. The method of claim 23 , wherein the test light is a partially polarized or an unpolarized light.
25. The method of claim 23 , wherein an incident angle of the test light differs from a calibration incident angle of the optical component by ±5°.