Scattering, interference, and switching of ultrashort surface plasmon polaritons

Ultrafast interactions of surface plasmon-polaritons (SPPs) in systems with multiple coherently excited SPP and light beams are studied. SPPs on thin metallic films are excited by local scattering of the laser light on surface nanostructures consisting of polymeric or metallic ridges [1] and grooves. SPP interaction and scattering effects are investigated by leakage radiation microscopy (LRM) [2]. The interference of SPPs inside dielectrically-loaded SPP waveguides [3] as well as the interference of SPPs with additional light fields is used for tracking the propagation of ultrashort SPP pulses excited by 60 fs laser pulses at a central wavelength of 800 nm. We present results on SPP autocorrelation, allowing the SPP dispersion and pulse durations to be measured. An example of a LRM image of an interference pattern of two counter-propagating SPPs inside a dielectrically-loaded waveguide is shown in Fig. 1. Furthermore, we demonstrate ultrafast scattering of propagating SPPs on regions of metal films pumped by additional laser pulses. In a time-delay pump-probe experiment it is shown that this SPP scattering occurs on the time scale of the pulse duration. Applications of this effect as ultrafast SPP switches are discussed.