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O: Fachverband Oberflächenphysik

O 7: Plasmonics and Nanooptics I

O 7.4: Vortrag

Montag, 18. März 2024, 11:15–11:30, MA 043

Ultrafast near-field scanning optical oscilloscopy — •Juanmei Duan, Tom Jehle, Sam Nochowitz, and Christoph Lienau — Universität Oldenburg, D-26129, Germany

Metallic, dielectric and hybrid nanoparticles offer exciting opportunities to localize, manipulate and switch light on the nanoscale. A direct measurement of the local electric field at the surface of the nanostructures is challenging however, since these fields are often localized on exceedingly short length and time scales. While experiments such as attosecond photoelectron emission microscopy or phase-resolved photon-induced near-field electron microscopy have been proposed, direct time-resolved measurements are still lacking. Here, we describe and demonstrate a new experimental technique, ultrafast near-field oscilloscopy, to probe coherent optical near-fields in the time with nanometer spatial resolution. For this, amplitude and phase of the local near-field scattered by a sharp metal taper are recorded in a broad spectral range and on a time scale that is faster than the tip modulation period. This allows us to record spectra as a function of tip-sample distance, the key to probe tip-sample coupling experimentally. Direct Fourier transform of the scattering spectra gives the local near-field dyanamics with sub-cycle temporal and nanometer spatial resolution. We demonstrate the versatility of this new approach by probing near-fields of dielectric and semiconducting nanoparticles, as well as different localized and propagating plasmon mode of metal nanostructures.

Keywords: sSNOM; Plasmonic nanostructures; spectral interferometry; Optical near fields