Significant Near Field Enhancement Over Large Volumes Around Metal Nanorods via Strong Coupling of Surface Lattice Resonances and Fabry-Pérot Resonance

Metal nanoparticles supporting plasmons are widely used to enhance electromagnetic fields, resulting in strong light-matter interactions at the nanoscale in a diverse range of applications. Recently, it has been shown that when metal nanorods are periodically arranged with proper lattice periods, surface lattice resonances (SLRs) can be excited and near fields can be greatly enhanced over extended volumes. In this work, we report significant near field enhancement over even larger volumes by placing the metal nanorod array within a Fabry-Pérot (F-P) microcavity. Results show that taking advantage of strong coupling between the SLR and the photonic F-P resonances, the electric field intensity of the bonding split mode can be enhanced by up to 1935 times, which is about three times of the enhancement of the SLR, and the greatly enhanced field can extend over most of the F-P microcavity. We further show that the F-P resonances of both odd and even orders can strongly couple to the SLR by varying the nanorods position from the middle of the microcavity. We expect that the proposed plasmonic-photonic coupling system will find promising applications in nanolasers, nonlinear optics and sensing.

Ultrahigh-Q Tunable Terahertz Absorber Based on Bulk Dirac Semimetal with Surface Lattice Resonance

In this paper, we present an easy-to-implement metamaterial absorber based on bulk Dirac semimetal (BDS). The proposed device not only obtains an ultrahigh quality factor (Q-factor) of 4133 and dynamic adjustability at high absorption, but also exhibits an excellent sensing performance with a figure of merit (FOM) of 4125. These outstanding properties are explained by the surface lattice resonance, which allows us to improve the quality factor significantly and control resonance wavelength precisely by tuning the unit cell periods, Fermi energy of the BDS, and structural parameters. Our findings can provide high-performance applications in terahertz filtering, detection, and biochemical sensing.

Strong Coupling Between Plasmonic Surface Lattice Resonance and Photonic Microcavity Modes

We report the strong coupling between plasmonic surface lattice resonances (SLRs) and photonic Fabry-Pérot (F-P) resonances in a microcavity embedded with two-dimensional periodic array of metal-insulator-metal nanopillars. For such a plasmonic-photonic system, we show that the SLR can be strongly coupled to the F-P resonances of both the odd- and even orders, and that the splitting energy reaches as high as 138 meV in the visible regime. We expect that this work will provide a new scheme for strong coupling between plasmonic and photonic modes.

Narrowband terahertz metasurface circular polarization beam splitter with large spectral tunability based on lattice-induced chirality

We propose a terahertz metasurface with chirality induced by surface lattice resonance for achieving narrowband circular polarization beam splitter (PBS) with large spectral tunability in both transmission and reflection modes. Results show that strong circular dichroism effects can be observed in two spectrally narrow bands, and thus a dual-band circular PBS can be achieved. We show that surface lattice resonance induces much narrower and stronger circular dichroism effects than localized resonance, resulting in higher polarization extinction ratios, higher quality factors, and more circular polarization states. The narrowband operation frequency of lattice-induced PBS with extinction ratio larger than 10 dB can be tuned over a large spectral range, from 1.6 THz to 2.3 THz, by varying the incidence angle. We expect the proposed strong, narrowband, and spectrally tunable circular PBS will find applications in polarization-dependent systems including imaging, spectroscopy, sensing and telecommunication in the terahertz regime.