A sharp and asymmetric line shape is numerically predicted in a novel and compact plasmonic waveguide system. This system consists of a groove and a ring resonator coupled with a metal-insulator-metal waveguide. Due to the interaction of the narrow discrete resonance and a broad spectrum caused by the ring resonator and the groove, respectively, the transmission spectrum exhibits a sharp asymmetrical profile. Simulation results show that the spectral line shape can be easily tuned by changing the parameters of the structure. The physical features contribute to a highly efficient plasmonic nanosensor for refractive index sensing with the sensitivity of 1160 nm/RIU and a figure of merit of 3200. This plasmonic structure with such high figure of merits may find important applications in the on-chip nanosensors.

Mid-infrared thermal detectors have very important applications in the aerospace and military fields. However, due to the low heat transfer efficiency and slow response time, their application has been greatly restricted. Here, we theoretically demonstrate a dual-band perfect absorber for a mid-infrared detector based on a dielectric metal metasurface, and the optical and thermal properties are analyzed in detail. Simulation results show that the two narrow absorption peaks, corresponding to the absorption value of 97.5% at λ = 6.142 μm with λ FWHM ≈ 40 nm and 99.7% at λ = 7.795 μm with λ FWHM ≈ 80 nm , respectively, are achieved, and their different dependences on the structural parameters have been studied. A thermal detector at room temperature with total response time within 1.3 ms for dual-band and 0.4 ms for single-band is realized when the incident light flux is 1.0 W / cm 2 for an average temperature increase of Δ T ≈ 1.0 K . Our study offers a promising approach for designing a narrowband mid-infrared perfect absorber and a high-performance photodetector in nano-integrated photonics.

Mid-infrared perfect absorbers (PAs) based on metamaterials have many applications in material analysis and spectral detection thanks to the associated strong light–matter interaction. Most of the PAs are built as ‘metal nanostructure’-insulator-metals (MIM). In this paper, we propose an ultra-narrow band absorber based on dielectric metasurface with a metal film substrate. The absorptance comes from the plasmonic absorption in the metal film, where the absorption is enhanced (while the band of that is compressed) by the super cavity effect of the dielectric metasurface. Based on our numerical calculation, the full-width at half-maximum (FWHM) can reach 67 nm at 8 μm (8‰), which is more than two orders of magnitude smaller than the resonance wavelength and much narrower than the theoretical FWHMs of MIM absorbers. Moreover, we studied their application in infrared thermal imaging, which also has more benefits than MIM absorbers. This kind of hybrid dielectric metasurface provides a new route to achieve ultra-narrow band perfect absorbers in the mid-infrared regime and can be broadly applied in detectors, thermal emitters and bio-spectroscopy.

Mode splitting is numerically predicted in a symmetry breaking plasmonic waveguide system, which consists of a metal–insulator–metal structure with a square cavity. By introducing a baffle in the square cavity, the anti-symmetric waveguide mode is excited and the transmission properties analyzed in detail. Simulation results show that we can obtain a longer resonant wavelength by only increasing the length of the baffle. Using the relationship between the length h and resonant wavelength λ , we can get a resonant cavity with a quality factor ( Q -factor) as high as Q ≈ 150. Furthermore, a compact 1 × 2 plasmonic wavelength demultiplexer is successfully achieved without increasing the total size of the structure, which is very conducive to integration. In addition, a refractive index sensor with a high sensitivity about 1320 nm/RIU is also realized. When the lateral symmetry of the structure is broken, the anti-symmetric waveguide mode splits into two high-order modes, and a typical Fano profile is also achieved. Our compact plasmonic structure may have potential applications in nanoscale optical switching, nanosensors, nanolasers, wavelength demultiplexers and slow-light devices in highly integrated optical circuits.

We theoretically propose blue-detuned optical trapping for neutral atoms via strong near-field interfacing in a plasmonic nanohole array. The optical field at resonance forms a nanoscale-trap potential with an FWHM of 200 nm and about $\sim 370\mathrm{nm}$ away from the nanohole; thus, a stable 3D atom trapping independent of the surface potential is demonstrated. The effective trap depth is more than 1 mK when the optical power of trapping light is only about 0.5 mW, while the atom scattering rate is merely about $3.31{\mathrm{s}}^{-1}$, and the trap lifetime is about 800 s. This compact plasmonic structure provides high uniformity of trap depths and a two-layer array of atom nanotraps, which should have important applications in the manipulation of cold atoms and collective resonance fluorescence.