We have investigated a novel approach for scattering-type scanning near-field optical microscopy that enables the direct visualization of surface polaritons – hybrid light-matter quasiparticles – in both space and time. Using plasmon polaritons in graphene as a model system, our approach demonstrates how propagating modes can be traced in the time domain with a straightforward mathematical framework, allowing the determination of the polariton’s group and phase velocities, as well as its damping. In combination with a pump–probe scheme, this method can resolve subcycle changes in polariton propagation upon photoexcitation, offering a powerful tool to study ultrafast nonequilibrium spatiotemporal dynamics. Beyond graphene, the technique is readily applicable to other quantum materials, providing a versatile approach for polariton nanoimaging.
The results obtained in close collaboration with the group of Miriam Vitiello in Pisa (NEST, CNR) and Eva A. A. Pogna in Milano (CNR-IFN) have been published in Nano Letters.
© Simon Anglhuber, UR
