Plasma dispersion effect for metasurface tuning
An active metasurface that provides low-loss and high-bandwidth modulation control of light includes a number of cells arranged on a substrate. A controller dynamically alters a voltage differential supplied to the electrodes of each of the cells is adapted to alter refractive index of each of the high-index dielectric blocks in order to controllably steer light exiting the cell.
1. A metasurface comprising:
a number of cells arranged on a substrate, each of the cells including:
a high-index dielectric block including an interface between a positively-doped material and a negatively-doped material; and
electrodes configured to provide a voltage differential across the high-index dielectric block to flow current along a current path that passes through the high-index dielectric block, at least a portion of the current path being substantially parallel to a plane defined by the metasurface; and
a controller that dynamically alters a voltage differential supplied to the electrodes of each of the cells to alter a refractive index of each of the high-index dielectric blocks in order to controllably steer light exiting the cell.
2. The metasurface of claim 1 , wherein each of the cells has dimensions that provide a Mie resonance mode to enhance an electric field component of light of a target wavelength.
3. The metasurface of claim 1 , wherein each of the cells is doped to have a positive charge density that increases in a first direction of the cell and a negative charge density that increases in a second opposite direction of the cell.
4. The metasurface of claim 3 , wherein the positive charge density and the negative charge density vary in a direction that is generally parallel to the plane defined by the metasurface.
5. The metasurface of claim 1 , wherein the high-index dielectric block is a silicon resonator.
6. The metasurface of claim 1 , wherein the cell is reverse biased such that the controller applies a positive voltage to a first electrode in contact with a negatively-doped region and a negative voltage to a second electrode that is in contact with a positively-doped region.
7. A method of controlling a metasurface to steer light, the method comprising:
receiving light at each of a number of cells arranged on a substrate, each of the cells including at least:
a high-index dielectric block including an interface between a positively-doped material and a negatively-doped material; and
electrodes configured to supply a voltage differential to the cell to flow current along a current path that passes through the high-index dielectric block, at least a portion of the current path being substantially parallel to a plane defined by the metasurface; and
dynamically altering a voltage differential supplied to the electrodes of each of the cells to alter a refractive index of each of the high-index dielectric blocks in order to controllably steer light exiting the cell.
8. The method of claim 7 , wherein each of the cells has dimensions that provide a Mie resonance mode to enhance an electric field component of light of a target wavelength.
9. The method of claim 7 , wherein each of the cells is doped to have a positive charge density that increases in a first direction of the cell and a negative charge density that increases in a second opposite direction of the cell.
10. The method of claim 9 , wherein the positive charge density and the negative charge density vary in a direction that is generally parallel to the plane defined by the metasurface.
11. The method of claim 9 , wherein the high-index dielectric block is a silicon resonator.
12. A system comprising:
at least one cell including a high-index dielectric block including a junction between a positively-doped material and a negatively-doped material;
electrodes arranged on opposite sides of the at least one cell and each being separated from a phase-shifting portion of the high-index dielectric block;
circuitry configured to supply a voltage differential to the electrodes and to dynamically alter the voltage differential to control a refractive index of the high-index dielectric block and thereby controllably steer light exiting the cell.