A Local Superlens

Superlenses enable near-field imaging beyond the optical diffraction limit. However, their widespread implementation in optical imaging technology so far has been limited by large-scale fabrication, fixed lens position, and specific object materials. Here we demonstrate that a dielectric lamella of subwavelength size in all three spatial dimensions behaves as a compact superlens that operates at infrared wavelengths and can be positioned to image any local microscopic area of interest on the sample. In particular, the lamella superlens may be placed in contact with any type of object and therefore enables examination of hard-to-scan samples, for example, with high topography or in liquids, without altering the specimen design. This lamella-based local superlens design is directly applicable to subwavelength light-based technology, such as integrated optics

Unveiling the plasma wave in the channel of graphene field-effect transistor

Coupling an electromagnetic wave at GHz to THz frequencies into the channel of a graphene field-effect transistor (GFET) provokes collective charge carrier oscillations of the two-dimensional electron gas (2DEG) known as plasma waves. Here, we report the very first experimental and direct mapping of the electric field distribution in a gated GFET at nanometer length scales using scattering-type scanning near-field microscopy (s-SNOM) at 2 THz. Based on the experimental results we deduce the plasma wave velocity for different gate bias voltages, which is in good agreement with the theoretical prediction.Peer reviewe