Metasurface operating in the transmission scheme has shown a promising scenario for flat optics applications. Nevertheless, the inherently low working efficiency of transmissive plasmonic metasurfaces at optical frequencies severely hinders them from future technology development. This work reports on a hybrid plasmonic meta‐atom (HPMA) with a simple fabrication and cost‐effective single‐lithographic process featuring a toroidal‐assisted generalized Huygens’ source with a state‐of‐the‐art circular polarization conversion efficiency beyond 50%. The HPMA representsa new upper limit for transmission efficiency in the near‐infrared. The high transmission is realized via balanced multipoles of different orders including toroidal dipole that satisfies the generalized Kerker condition. The introduction of toroidal dipole provides an additional degree of freedom to tailor the wave interference and radiation symmetry rather than the use of a conventional electric and magnetic multipolar coupling. In addition, two high‐performance metasurfaces by combining the HPMAs with the geometric phase method are highlighted. The highly‐transmissive beam deflection metasurface and plasmonic metalens respectively yield anomalous refraction with 38.2% optical efficiency and 46.56% focusing efficiency, both experimentally showing a record transmission level. The findings may open new ways to design highly‐efficient plasmonic metasurfaces and to take one step forward to facilitate nearly optimal and practical nanophotonic devices.

The recent progress in plasmonic metasurfaces gives rise to an intense evolution of controlling light properties such as phase, amplitude, polarization, and frequency. In this work, a new paradigm is established to control the light properties centered on low‐loss toroidal multipoles with high field enhancement in contrast to most of the previous plasmonic metasurfaces that are optimized through electric and magnetic multipolar resonances. Through a proof‐of‐concept demonstration, a linear cross‐polarization conversion efficiency reaching 22.9%, remarked as the optimal value that can exist in a single‐layer plasmonic metasurface in the near‐infrared spectrum, is experimentally realized. A polarization‐insensitive toroidal response, that previously was accessible only in isotropic high‐index metasurfaces, is also observed. Furthermore, a giant anisotropic (polarization‐sensitive) generation of the second‐harmonic frequency is demonstrated with the proposed polarization‐independent toroidal metasurface that provides different levels of electric energy storage within the metasurface. These findings open a new path for keeping low‐efficiency plasmonic components on track when one engineers a metasurface based on the toroidal multipole family.

Reexamining the plasmonic metasurfaces for efficient transmissive nanophotonics devices has recently drawn considerable attention. It attributes to their ease of fabrication and tunability in terms of the excitation of abundant multipoles. Despite recent efforts in developing plasmonic meta‐atoms, meta‐gratings provide an ultimate solution that enables efficient conversion of the polarization in a broadband range, particularly at optical frequencies. In this work, by vertically stacking meta‐gratings whose bandwidths overlap with each other and possess no physical limitation, plasmon mode hybridization is introduced so that highly‐transmissive broadband plasmonic metasurfaces are realized. It is reported that the intra‐coupling in a discrete plasmonic meta‐grating plays a key role in geometric phase‐controlled metasurface design. As a proof of concept, a half‐wave plate using plasmonic meta‐gratings to convert the incident circularly‐polarized light in a wavelength range from 1106 to 1521 nm with a peak efficiency of 50.2% and a gradient metasurface with truncated discrete meta‐grating as building blocks for deflecting the light with a maximum of 32.60% are demonstrated. Finally, the physical picture is explained through the electric field distributions, mode coupling, and energy splitting. The presented framework may provide an optimized way to enhance efficiency and expand the bandwidth for plasmonic systems.

Manipulating polarization states of microlasers is essentially important in many emerging optical and biological applications. Strategies have been focused on using external optical elements or surface nanostructures to control the polarization state of laser emission. Here we introduce a strategy for manipulation of laser polarization based on metasurfaces through round trips of photons confined inside an active optical cavity. The roles of intracavity metasurfaces and light–meta-atom interactions were investigated under a stimulated emission process in a microcavity. Taking advantage of strong optical feedback produced by the Fabry–P e ´ rot optofluidic microcavity, light–meta-atom interactions are enlarged, resulting in polarized lasing emission with high purity and controllability. Depending on the metasurface structural orientation, the polarization state of lasing emission can be actively modulated as linearly polarized or elliptically polarized with different degrees of circular polarization at a source within the microcavity. This study provides insight into fundamental laser physics, opening possibilities by bridging metasurfaces into microlasers.

Optical coupling plays a pivotal role in nanophotonic systems, which can be divided into weak, intermediate, and strong‐coupling regimes. Monitoring optical coupling strength is, therefore, the key to understanding light–matter interactions. State‐of‐the‐art approaches based on spectral measurements offer the power to quantify and characterize optical coupling strength at a single cavity level. However, it remains challenging to dynamically characterize coupling strength during the transition from strong‐ to weak‐coupling regimes for many systems simultaneously. Here, a far‐field imaging technique is reported that can directly monitor optical coupling dynamics in plasmon–exciton systems, allowing multiple nanocavity emissions to be characterized from weak‐ to strong‐coupling regimes. Light‐harvesting biomolecules—chlorophyll‐a—is employed to study dynamic light–matter interactions in strongly coupled plasmonic nanocavities. Identification of coupling strength is achieved by extracting red, green, and blue (RGB) values from dark‐field images and an enhancement factor from fluorescence images. Lastly, the ability to monitor subtle changes of coupling dynamics in bioplasmonic nanocavity is demonstrated. These findings may deepen the understanding in light–matter interactions, paving new avenues toward applications in quantum‐based biosensing and imaging.