The plasmonic color filter with a suitable bandwidth, high transmittance is usually regarded as an essential optical element for a variety of utilization. Here, we propose an ultra-thin plasmonic color filter based on a substrate free dielectric film waveguide composed of two sizes of metal-disk. The proposed plasmonic filter operates through the hybrid role of surface plasmon polariton (SPP) mode, the localized Fabry-Perot resonance, and waveguide mode. The filter consists of a waveguide layer (Si3N4), a buffer layer (MgF2) and a nanodisk (Al). This paper uses the finite difference time domain (FDTD) method. The boundary condition is the boundary condition of the perfectly matched layer(PML) with anisotropy in Y direction, and the periodic boundary condition is selected in X and Z directions. In this paper, the influence of the thickness of the waveguide layer, the thickness of the buffer layer and the nanodisk period on the transmission spectrum is discussed, and the polarization-dependence of the filter is also discussed. The results demonstrate that the filter has more than 80% transmittance and is related to polarization and can be implemented to color display and integrated optoelectronic devices.
A surface plasmon resonance (SPR) sensor on an optical fiber endface with metallic rectangular slit array structure is presented. The finite-difference time-domain (FDTD) method was utilized to study the influence of structural parameters on the transmission spectrum and the refractive index (RI) sensing characteristic based on the two transmission peaks. The proposed sensor is compact and has the potential to be used in biomedical applications, having two transmission peaks with a sensitivity of 1209 and 500 nm per refractive index unit (RIU) respectively.
A new kind of tunable multi-channel wavelength demultiplexer (WDM) based on metal-insulator-metal (MIM) plasmonic nanodisk resonators with a metal block is proposed. The transmission properties of such structure are simulated by the Finite-Difference Time-Domain (FDTD) method, and the eignwavelengths of the disc resonator are calculated theoretically. It is found that the transmission characteristics of the filter can be easily adjusted by changing the geometrical parameters of the metal block of the nanodisk. The multi-channel WDM structure consisting of a plasmonic waveguide and several nanodisk resonators with metal block, by changing the parameter of metal block of nanodisk resonators, the filter shows the resonant mode filter function. Basing on this characteristic, a three-port wavelength demultiplexer is designed, which can separate resonant modes inside the nanodisk with high transmission up to 60%. It can find important potential applications in highly integrated optical circuits.
An infrared (IR) absorber based on the metamaterial structure is proposed theoretically and numerically. The near-unity absorption can be achieved at a certain wavelength by optimizing geometrical parameters of the structure. Moreover, we can switch a single-band absorber to dual-band absorber by decreasing the thickness of top metallic layer which is perforated by an air-filled ribbon. At the same time, we confirm that the mechanism of this two absorption bands is completely different. The simultaneous effects of the magnetic resonance and the cavity resonance occur at our proposed structure. Besides according to the control of polarization direction, the absorption peaks occur at the two constant wavelengths, and the superposed value of this two absorption peaks is always close to a constant. Based on this phenomenon, a simple dual-band absorber is designed when the thickness of top shaped metallic film is relatively large. The cavity response is not the existence in this condition. These results that we obtain may provide some promising applications such as sensors, thermal imagers, and IR detectors.