Bowtie nanoantennas and methods of using the same
A pillar-nanoantenna array structure is fabricated with a substrate to which pairs of pillars are coupled, where the pillars are characterized either by a thermal conductance less than 0.1 μW/deg or by transparency and a height exceeding thickness by at least a factor of two. Metallic caps atop a neighboring pair of pillars are separated by no more than 50 nm. An image-capture structure may be formed by modifying reflectance of a portion of the structure by heating of the portion by electromagnetic radiation. The array may be plastically deformed by raster scanning an electron beam across the array, exciting plasmon modes in the conducting particles thereby inducing a gradient force between neighboring conducting particles, and deforming neighboring pillars in such a manner as to vary the spacing separating neighboring conducting particles. A technique of plasmon-assisted etching provides for fabricating specified planar pattern of metal outside a cleanroom environment.
1. A method for producing a custom plasmonic potential energy landscape for optically trapping particles, the method comprising:
a. forming a structure that comprises an array of pillars coupled to a substrate having a substantially planar surface, the pillars characterized by a thermal conductance less than 0.1 μW/deg, the pillars capped by a conducting particle atop each insulating pillar such that pairs of neighboring conducting particles are separated with respect to each other by no more than 50 nm; and
b. deforming neighboring pillars in such a manner as to plastically vary a spacing separating neighboring conducting particles in a specified pattern.
2. A method in accordance with claim 1 , wherein deforming neighboring pillars comprises exciting plasmon modes in the conducting particles with an electron beam thereby inducing a gradient force between neighboring conducting particles.
3. A method in accordance with claim 1 , wherein the conducting particles include substantially metallic caps.
4. A method in accordance with claim 3 , wherein the metallic caps are substantially triangular.
5. A method in accordance with claim 1 , wherein the substrate includes a substantially planar surface.
6. A method in accordance with claim 1 , wherein the pillars are substantially transparent in a specified portion of the electromagnetic spectrum.
7. A method in accordance with claim 1 , wherein the substrate and the pillars are composed of an identical material.
8. A method in accordance with 5 , further comprising depositing a layer of conducting material intervening between the substantially planar surface of the substrate and the pillars.
9. A method in accordance with claim 1 , wherein the substrate and the pillars are SiO 2 .
10. A method in accordance with claim 8 , wherein the step of depositing a layer of conducting material intervening between the substantially planar surface of the substrate and the pillars includes depositing indium tin oxide.