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Graphene can support surface plasmons with higher confinement, lower propagation loss, and substantially more tunable response compared to usual metal-based plasmonic structures. Interestingly, plasmons in graphene can strongly couple with nanostructures and gratings placed in its vicinity to form new hybrid systems that can provide a platform to investigate more complicated plasmonic phenomena. In this Perspective, an analysis on the excitation of highly confined graphene plasmons and their strong coupling with metallic or dielectric gratings is performed. We emphasize the flexibility in the efficient control of light–matter interaction by these new hybrid systems, benefiting from the interplay between graphene plasmons and other external resonant modes. The hybrid graphene-plasmon grating systems offer unique tunable plasmonic resonances with enhanced field distributions. They exhibit a novel route to realize practical emerging applications, including nonreciprocal devices, plasmonic switches, perfect absorbers, nonlinear structures, photodetectors, and optical sensors.

Nonreciprocal thermal emission is a cutting-edge technology that enables fundamental control over thermal radiation and has exciting applications in thermal energy harvesting. However, thus far one of the foremost challenges is making nonreciprocal emission operate over a broad wavelength range and for multiple angles. In this work, we solve this outstanding problem by proposing three different types of structures that always utilize only one Weyl semimetal (WSM) thin film combined with one or two additional dielectric or metallic layers and terminated by a metallic substrate. First, a tradeoff relationship between the magnitude and bandwidth of the thermal nonreciprocity contrast is established based on the thickness of the WSM film. Then, the bandwidth broadening effect is demonstrated via the insertion of a dielectric spacer layer that can also be fine-tuned by varying its thickness. Finally, further control on the resulting strong nonreciprocal thermal radiation is demonstrated by the addition of a thin metallic layer in the proposed few layer designs. The presented composite structures work for a broad frequency range and for multiple emission angles, resulting in highly advantageous properties for various nonreciprocal thermal radiation applications. Moreover, the proposed designs do not require any patterning and can be experimentally realized by simple deposition fabrication methods. They are expected to aid in the creation of broadband nonreciprocal thermal emitters that can find applications in new energy harvesting devices.

Parity-time (PT) symmetric optical structures exhibit several unique and interesting characteristics, with the most popular being exceptional points. While the emerging concept of PT-symmetry has been extensively investigated in bulky photonic designs, its exotic functionalities in nanophotonic non-Hermitian plasmonic systems still remain relatively unexplored. Towards this goal, in this work we analyze the unusual properties of a plasmonic Huygens’ metasurface composed of an array of active metal-dielectric core-shell nanoparticles. By calculating the reflection and transmission coefficients of the metasurface under various levels of gain, we demonstrate the existence of reflectionless transmission when an exceptional point is formed. The proposed new active metasurface design has subwavelength thickness and can be used to realize ultracompact perfect transmission optical filters.

Controlling the spectral and angular response of infrared (IR) radiation is a challenging task of paramount importance to various emerging photonic applications. Here, we overcome these problems by proposing and analyzing a new design of a tunable narrowband directional optical transmission filter. The presented thermally controlled multilayer filter leverages the temperature dependent phase change properties of vanadium dioxide (VO₂) to enable efficient and reversible fast optical switching by using a pump-probe laser excitation setup. More specifically, transmission is blocked for high intensity probe lasers due to the VO₂metallic properties induced at elevated temperatures while at low probe laser intensities high transmission through the filter occurs only for a narrowband IR range confined to near normal incident angles. The proposed multilayer composite dielectric filter is expected to have applications in optical communications, where it can act as dual functional infrared filter and optical switch.