title: Photoinduced Force Mapping of Plasmonic Nanostructures.
abstract: The ability to image the optical near-fields of nanoscale structures, map their morphology, and concurrently obtain spectroscopic information, all with high spatiotemporal resolution, is a highly sought-after technique in nanophotonics. As a step toward this goal, we demonstrate the mapping of electromagnetic forces between a nanoscale tip and an optically excited sample consisting of plasmonic nanostructures with an imaging platform based on atomic force microscopy. We present the first detailed joint experimental-theoretical study of this type of photoinduced force microscopy. We show that the enhancement of near-field optical forces in gold disk dimers and nanorods follows the expected plasmonic field enhancements with strong polarization sensitivity. We then introduce a new way to evaluate optically induced tip-sample forces by simulating realistic geometries of the tip and sample. We decompose the calculated forces into in-plane and out-of-plane components and compare the calculated and measured force enhancements in the fabricated plasmonic structures. Finally, we show the usefulness of photoinduced force mapping for characterizing the heterogeneity of near-field enhancements in precisely e-beam fabricated nominally alike nanostructures - a capability of widespread interest for precise nanomanufacturing, SERS, and photocatalysis applications.
authors.affiliation: Department of Electrical and Computer Engineering, ‡Department of Physics and Astronomy, §Department of Chemistry, ∥Laboratory for Nanophotonics, ⊥Rice Quantum Institute, and #Department of Materials Science and NanoEngineering, Rice University , 6100 Main Street, Houston, Texas 77005, United States.
authors.forename: Thejaswi U
authors.initials: TU
authors.lastname: Tumkur
authors.affiliation: Department of Electrical and Computer Engineering, ‡Department of Physics and Astronomy, §Department of Chemistry, ∥Laboratory for Nanophotonics, ⊥Rice Quantum Institute, and #Department of Materials Science and NanoEngineering, Rice University , 6100 Main Street, Houston, Texas 77005, United States.
authors.forename: Xiao
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Electrical and Computer Engineering, ‡Department of Physics and Astronomy, §Department of Chemistry, ∥Laboratory for Nanophotonics, ⊥Rice Quantum Institute, and #Department of Materials Science and NanoEngineering, Rice University , 6100 Main Street, Houston, Texas 77005, United States.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Cerjan
authors.affiliation: Department of Electrical and Computer Engineering, ‡Department of Physics and Astronomy, §Department of Chemistry, ∥Laboratory for Nanophotonics, ⊥Rice Quantum Institute, and #Department of Materials Science and NanoEngineering, Rice University , 6100 Main Street, Houston, Texas 77005, United States.
authors.forename: Naomi J
authors.initials: NJ
authors.lastname: Halas
authors.affiliation: Department of Electrical and Computer Engineering, ‡Department of Physics and Astronomy, §Department of Chemistry, ∥Laboratory for Nanophotonics, ⊥Rice Quantum Institute, and #Department of Materials Science and NanoEngineering, Rice University , 6100 Main Street, Houston, Texas 77005, United States.
authors.forename: Peter
authors.initials: P
authors.lastname: Nordlander
authors.affiliation: Department of Electrical and Computer Engineering, ‡Department of Physics and Astronomy, §Department of Chemistry, ∥Laboratory for Nanophotonics, ⊥Rice Quantum Institute, and #Department of Materials Science and NanoEngineering, Rice University , 6100 Main Street, Houston, Texas 77005, United States.
authors.forename: Isabell
authors.initials: I
authors.lastname: Thomann
keywords: Plasmonics; gradient force; nanocharacterization; near-field scanning optical microscopy; photocatalysis