Abstract
In the first part of the talk, I will briefly introduce our home-built momentum-space imaging spectroscopy based on conventional Fourier transform. Two techniques are exploited to “mine” the rich optical information contained in Fourier images. Iso-frequency contours and dispersion relations of photonic-crystal slabs and planar plasmonic crystals can be measured without rotating samples, from which “3D” band structures of polarization-resolved reflection, transmission, absorption or even emission can be constructed.
In the second part, I will present our recent results on the observations of topological vortices in planar plasmonic crystals in the visible range. Based on our home-built momentum-space imaging spectroscopy, we map out the band structures, lifetimes, and polarization states of the radiative modes. Polarization vortices with topological charge of 1 and 2 are observed in square and hexagonal lattices. Those with fractional charge (1/2) are also found.
Anyone interested is welcome to attend.