Ultrafast Nanooptics: Plasmonenkopplung, Propagation und Interferenz auf der Nanoskala, unter Beobachtung mit Femotosekunden Photoemissionsmikroskopie

The coupling of light into metallic structures, and the guiding, manipulation, and conversion back into light is extremely desirable, because this would revolutionize modern telecommunication and computing technology. The optical losses in metals are too large to transport light directly, however, and the light must be converted into a surface plasmon polariton (SPP), i.e., a charge-density wave that propagates at the interface between the metallic surface and the surrounding medium. In his previous work, the applicant has developed a technique to visualize SPP waves at the surface of Ag islands with two photon photoemission microscopy (2PPE PEEM). 2PPE PEEM relies on femtosecond (fs) laser pulses for illumination of the surface and provides plasmon-enhanced nonlinear photoemission images with video rate. During the first funding period, the applicant demonstrated that 2PPE PEEM can be used to study the excitation of SPPs with fs laser pulses, that SPP propagation can be observed, and that 2PPE PEEM is suitable to study the coupling of SPPs back into light. By covering the surface of an Ag island by only a few nm C60, the properties of the SPP were gradually changed. The present proposal aims at a fundamental understanding of the SPP propagation and interaction with matter. In the newly developed normal incidence (NI) geometry in 2PPE PEEM, the plasmon-related contrast provides a more detailed picture of the propagating SPP. Using NI in a pump-probe experiment, it should be possible to observe a SPP wave packet directly while it travels across the surface, is reflected, or is converted back into light. Using SPP interference and controlled phase shifts between pump and probe pulses of different polarizations, the optical near field behind the islands will be controlled with a resolution close to the diffraction limit.

DFG-Verfahren Schwerpunktprogramme

Teilprojekt zu SPP 1391:  Ultrafast Nanooptics