Polariton nanophotonics using phase-change materials

Abstract

Polaritons formed by the coupling of light and material excitations enable light-matter interactions at the nanoscale beyond what is currently possible with conventional optics. However, novel techniques are required to control the propagation of polaritons at the nanoscale and to implement the first practical devices. Here we report the experimental realization of polariton refractive and meta-optics in the mid-infrared by exploiting the properties of low-loss phonon polaritons in isotopically pure hexagonal boron nitride interacting with the surrounding dielectric environment comprising the low-loss phase change material Ge3Sb2Te6. We demonstrate rewritable waveguides, refractive optical elements such as lenses, prisms, and metalenses, which allow for polariton wavefront engineering and sub-wavelength focusing. This method will enable the realization of programmable miniaturized integrated optoelectronic devices and on-demand biosensors based on high quality phonon resonators.

Infrared Permittivity of the Biaxial van der Waals Semiconductor α‐MoO3 from Near‐ and Far‐Field Correlative Studies

“…Polaritons—hybrid light–matter excitations—in hyperbolic media have opened up new avenues for studying exotic optical phenomena, such as non‐reciprocal Purcell enhancement, [ 1 ] negative refraction, [ 2 ] non‐reciprocal polariton guiding, [ 3 ] reconfigurable metaoptics, [ 4,5 ] topological transitions of in‐plane anisotropic polaritons, [ 6 ] and directional nanoscale energy collimation. [ 7,8 ] Excitingly, PhPs with in‐plane hyperbolic and elliptic dispersion have been recently discovered in the biaxial van der Waals (vdW) semiconductor α‐MoO 3 within a series of spectral bands—the so‐called Reststrahlen bands (RBs)—throughout the long‐wave infrared range [ 9–11 ] (LWIR).…”

“…Building on prior efforts utilizing local changes in the dielectric environment, [ 41 ] advanced concepts for reconfigurable planar metaoptics can be realized. [ 5,41 ] More broadly, structuring biaxial materials may offer new opportunities for making both passive and light emitting structures with unusual polarization states [ 8 ] —as in the creation of circularly polarized light. Furthermore, it may open new regimes for highly anisotropic dielectric resonators within the highly dispersive, extreme permittivity regime at frequencies below the TO phonon.…”

Refractive Index-Based Control of Hyperbolic Phonon-Polariton Propagation

“…where the change in frequency of polaritonic resonance indicates a change in the local dielectric environment, we consider the analytical model for both surface phonon polaritons (SPhPs) and HPhPs. At mid-IR frequencies, strongly confined HPhPs and environmental sensitivity in hBN-enabled surface-enhanced infrared absorption (SEIRA)[46][47][48] spectroscopy and suggested a basis for planar metaoptics structures 2 that have since reduced to practice 17. These new results also have implications for deploying hBN in thin-film sensing applications.…”

Alignment-free difference frequency light source tunable from 5 to 20 µm by mixing two independently tunable OPOs

“…The application of ultrafast MIR lasers with high repetition rates for spectroscopy has enabled a variety of novel research topics, which have not been feasible before. Among many others, in vitro monitoring of structural processes in protein research at attomolar concentrations in far-field spectroscopy [1], or of individual protein complexes in near-field spectroscopy [2], monitoring the hydrogen diffusion into metal hydrides [3], or the characterization of novel materials for miniature optoelectronic devices in the fingerprint region [4][5][6][7] are just a few examples. The modern world is based on highly technical processes and their impact will further grow in search of solutions for renewable energy sources, environmentally friendly transportation, remote sensing, life sciences, or for the growing digitization.…”