4 research outputs found
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