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Near-field radiative heat transfer (NFRHT) can exceed the blackbody limit by several orders of magnitude owing to the tunneling evanescent waves. Exploiting this near-field enhancement holds significant potential for emerging technologies. It has been suggested that coupled polaritons can give rise to orders of magnitude enhancement of NFRHT. However, a thorough experimental verification of this phenomenon is still missing. Here this work experimentally shows that NFRHT mediated by coupled polaritons in millimeter-size graphene/SiC/SiO 2 composite devices in planar plate configuration can realize about 302.8 ±  35.2-fold enhancement with respect to the blackbody limit at a gap distance of 87  ±  0.8 nm. The radiative thermal conductance and effective gap heat transfer coefficient can reach unprecedented values of 0.136 WK -1 and 5440 Wm -2 K -1 . Additionally, a scattering-type scanning near-field optical measurement, in conjunction with full-wave numerical simulations, provides further evidence for the coupled polaritonic characteristics of the devices. Notably, this work experimentally demonstrates dynamic regulation of NFRHT can be achieved by modulating the bias voltage, leading to an ultrahigh dynamic range of ≈4.115. This work ambiguously elucidates the important role of coupled polaritons in NFRHT, paving the way for the manipulation of nanoscale heat transport, energy conversion, and thermal computing via the strong coupling effect., (© 2024 Wiley‐VCH GmbH.)

Owning to their unusual optical properties, such as electrical tunability and strong spatial confinement, two-dimensional surface polaritons (2DSPs) hold great promise for deep sub-wavelength manipulation of light in a reduced low-dimensional space. Control of 2DSPs is possible by using their interaction with a boundary between two media, similar to how light behaves in three-dimensional (3D) space. The understanding of the interaction in the 2D case is still in its early stages, unlike the 3D case, as in-depth investigations are only available in a few cases including the interaction of 2DSPs with structured 2D crystals. Here, we extend the scope of our understanding to the interaction of 2DSPs with metallic nano-plates on 2D crystals, focusing on the reflection of 2DSPs. Through our rigorous model, we reveal that, for strongly confined 2DSPs having much larger momentum than free space photons, the interaction results in almost total internal reflection of 2DSPs as the radiative coupling of the 2DSPs to free space is negligible. We also find that the reflection involves an anomalous phase shift dependent on the thickness of the nano-plate, due to the temporary storing of electromagnetic energy in the evanescent waves induced near the edge of the nano-plate. Our theory predicts that the phase shift saturates to an anomalous value, 0.885 π , as the nano-plate becomes thicker. Our work provides a detailed understanding of how to manipulate the 2DSPs by using one of the simplest nanostructures, essential for the further development of nanostructure-integrated low-dimensional devices for polariton optics., (© 2023 the author(s), published by De Gruyter, Berlin/Boston.)

Due to ultrabright and stable blue light emission, GaN has emerged as one of the most famous semiconductors of the modern era, useful for light-emitting diodes, power electronics, and optoelectronic applications. Extending GaN's optical resonance from visible to mid- and-far-infrared spectral ranges will enable novel applications in many emerging technologies. Here we show hexagonal honeycomb-shaped GaN nanowall networks and vertically standing nanorods exhibiting morphology-dependent Reststrahlen band and plasmon polaritons that could be harnessed for infrared nanophotonics. Surface-induced dipoles at the edges and asperities in molecular beam epitaxy-deposited nanostructures lead to phonon absorption inside the Reststrahlen band, altering its shape from rectangular to right-trapezoidal. Excitation of such surface polariton modes provides a novel pathway to achieve far-infrared optical resonance in GaN. Additionally, surface defects in nanostructures lead to high carrier concentrations, resulting in tunable mid-infrared plasmon polaritons with high-quality factors. Demonstration of morphology-controlled Reststrahlen band and plasmon polaritons make GaN nanostructures attractive for infrared nanophotonics.

Enhancement of weak Casimir forces is extremely important for their practical detection and subsequent applications in variety of scientific and technological fields. We study the lateral Casimir forces acting on the rotating particles with small radius of 50 nm as well as that with large radius of 500 nm near the hyperbolic metamaterial made of silicon carbide (SiC) nanowires. It is found that the lateral Casimir force acting on the small particle of 50 nm near hyperbolic metamaterial with appropriate filling fraction can be enhanced nearly four times comparing with that acting on the same particle near SiC bulk in the previous study. Such enhancement is caused by the coupling between the resonance mode excited by nanoparticle and the hyperbolic mode supported by hyperbolic metamaterial. The results obtained in this study provide an efficient method to enhance the interaction of nanoscale objects., (© 2022 IOP Publishing Ltd.)

Infrared nanospectroscopy based on Fourier transform infrared near-field spectroscopy (nano-FTIR) is an emerging nanoanalytical tool with large application potential for label-free mapping and identification of organic and inorganic materials with nanoscale spatial resolution. However, the detection of thin molecular layers and nanostructures on standard substrates is still challenged by weak signals. Here, we demonstrate a significant enhancement of nano-FTIR signals of a thin organic layer by exploiting polariton-resonant tip-substrate coupling and surface polariton illumination of the probing tip. When the molecular vibration matches the tip-substrate resonance, we achieve up to nearly one order of magnitude signal enhancement on a phonon-polaritonic quartz (c-SiO 2 ) substrate, as compared to nano-FTIR spectra obtained on metal (Au) substrates, and up to two orders of magnitude when compared to the standard infrared spectroscopy substrate CaF 2 . Our results will be of critical importance for boosting nano-FTIR spectroscopy toward the routine detection of monolayers and single molecules.

Surface plasmon resonance has become a widely accepted optical technique for studying biological and chemical interactions. Among others, detecting small changes in analyte concentration in complex solutions remains challenging, e.g., because of the need of distinguishing the interaction of interest from other effects. In our model study, the resolution ability of plasmonic sensing element was enhanced by two ways. Besides an implementation of metal-insulator-metal (MIM) plasmonic nanostructure, we suggest concatenation with waveguiding substructure to achieve mutual coupling of surface plasmon polariton (SPP) with an optical waveguiding mode. The dependence of coupling conditions on the multilayer parameters was analyzed to obtain optimal field intensity enhancement.

Here we report on the analysis of the effect of the doping of CdP 2 single crystals by ZnP 2 nanoclusters on the dispersion of the surface polaritons (SP). The ATR spectroscopic technique has been applied to excite the SP in the Cd X Zn (1-X) P 2 system. Analysis of the obtained spectra has shown that the doping of CdP 2 single crystals by ZnP 2 nanoclusters result in the position and the width of the dispersion branches of the SP. This effect is more pronounced in the low frequency dispersion branches. These SP branches are originated from phonons which correspond to the motion of the cation sublattice.

An investigation of the infrared (IR) spectra of polyoxymethylene (POM) mold plates was undertaken to determine the sub-micron-scale morphology and molecular orientation. The nest-structured cells concerned with the orientation were observed from scanning electron microscope (SEM) measurements with the aid of Raman spectroscopy. The intensity of the anomalous IR reflectance peak of the C-O stretching A2 mode depends on the widths of the POM layers in the SEM image along the orientation direction. The results suggest that the spectral features originate from the Berreman effect of the bulk polaritons and the radiative surface polaritons. Moreover, the IR spectra of certain treated samples suggest that enhancement of the electromagnetic fields from the gap modes and transition dipole-dipole coupling influence the spectral shapes., (© The Author(s) 2016.)

We report a remotely mediated and fast responsive plasmonic-magnetic nanorod array with extremely large variability in optical appearance (up to 100 nm shifts in scattering maxima) and concurrently for multiple wavelengths in a broad range from UV-vis to near-infrared (at 450, 550, and 670 nm) with an external magnetic field with variable direction. The observed phenomenon demonstrates a rapid, wide-range response controlled via a noninvasive remote stimulus. The remotely controlled system suggested here is a magnetic field-directed assembly of an ordered monolayer array of unipolar oriented magnetic-plasmonic nickel-gold nanorods flexibly hinged to a sticky substrate. The unique geometry of the mobile nanorod array allows for the instant alteration of the surface plasmon polariton modes in the gold segment of the controllably tilting nanorods. This design demonstrates the utility of hybrid bimetallic nanoparticles and gives a novel approach to the design of fast-acting, remotely controlled color-changing nanomaterials for sensing and interfacial transport.