1 research outputs found
Twisted Nano-optics: Manipulating Light at the Nanoscale with Twisted Phonon Polaritonic Slabs
Recent discoveries have shown that when two layers of van der Waals (vdW)
materials are superimposed with a relative twist angle between their respective
in-plane principal axes, the electronic properties of the coupled system can be
dramatically altered. Here, we demonstrate that a similar concept can be
extended to the optics realm, particularly to propagating polaritons, hybrid
light-matter interactions. To do this, we fabricate stacks composed of two
twisted slabs of a polar vdW crystal (MoO3) supporting low-loss anisotropic
phonon polaritons (PhPs), and image the propagation of the latter when launched
by localized sources (metal antennas). Our images reveal that under a critical
angle the PhPs isofrequency curve (determining the PhPs momentum at a fixed
frequency) undergoes a topological transition. Remarkably, at this angle, the
propagation of PhPs is strongly guided along predetermined directions
(canalization regime) with no geometrical spreading (diffraction-less). These
results demonstrate a new degree of freedom (twist angle) for controlling the
propagation of polaritons at the nanoscale with potential for nano-imaging,
(bio)-sensing, quantum applications and heat management