RF diffractive element with dynamically writable sub-wavelength pattern spatial definition
A spatial modulator for RF beams (microwave (uW), millimeter wave (MMW), and sub-millimeter wave (sub-MMW)) using dynamically-writable highly-reflective regions, with sub-wavelength diffractive pattern spatial definition that is finer than the wavelength of the incident RF beam.
1. A phase modulator for radio-frequency (RF) electromagnetic waves at a first range of frequencies, the phase modulator comprising:
a) RF reflective regions at a plurality of physical levels, the physical levels being separated by one or more RF phase-delay layers; and
b) one or more dynamically writable reflective regions at one or more physical levels, the dynamically writable reflective regions having pattern spatial definition finer than the wavelength of the electromagnetic waves at the first range of frequencies.
2. The apparatus of claim 1 , wherein the dynamically writeable reflective regions are plasmas in one or more semiconductor layers.
3. The apparatus of claim 2 , wherein the semiconductor layer has a thickness on the order of magnitude of the electromagnetic skin depth of the electromagnetic waves in the plasma.
4. The apparatus of claim 2 , wherein the plasma is written with photons with energy greater than the semiconductor bandgap of a semiconductor layer.
5. The apparatus of claim 4 , wherein the absorption depth in the semiconductor layer at the photonic wavelength is on the order of magnitude of the skin depth of the electromagnetic wave in the plasma.
6. The apparatus of claim 4 , wherein the apparatus includes optical antireflective structures, so as to reduce surface reflections of the photons.
7. The apparatus of claim 1 , wherein the dynamically writable reflective regions are dynamically erasable.
8. The apparatus of claim 7 , wherein the dynamically writable reflective regions are erased through recombination and thermalization of the plasma.
9. The apparatus of claim 7 , wherein the dynamically writable reflective regions are erased through voltage field biasing and removal at one or more electrodes.
10. The apparatus of claim 2 , wherein the plasma is confined by one or more electrically-insulating structures.
11. The apparatus of claim 1 , wherein the reflective regions are operably engaged.
12. The apparatus of claim 11 , wherein the apparatus includes antireflective structures.
13. The apparatus of claim 11 , wherein the apparatus includes thermally-conductive structures.
14. The apparatus of claim 2 , wherein the semiconductor layer surface is passivated, so as to increase carrier lifetime.
15. The apparatus of claim 2 , wherein the semiconductor layer surface is doped, so as to reduce carrier lifetime.
16. The apparatus of claim 4 , further comprising a photon patterning system selected from a group consisting of: a digital micromirror device, a grating light valve device, an addressable laser array, an addressable light emitting diode array, and a liquid crystal device.
17. The apparatus of claim 1 , wherein the modulator is bendable.
18. The apparatus of claim 1 , wherein the pattern is selected from a group consisting of: patch resonators, ring resonators, split-ring resonators, U-shaped resonators, V-shaped resonators and rod resonators.
19. The apparatus of claim 1 , wherein a portion of the reflective regions are metallic elements.