An ultrawideband metamaterial perfect absorber based on vanadium dioxide is proposed. It achieves >95 % absorption of vertically incident electromagnetic waves in the range of 3.50 to 10 THz. The absorption intensity can be dynamically adjusted in the range of 0.2% to 99.98% by varying the conductivity of VO2. The mechanism of ultrawideband perfect absorption is interpreted using electric field distribution analysis and impedance-matching theory. The absorption rate related to the structural parameters of the absorber is investigated by numerical simulation. Finally, its polarization angle-insensitive and incidence angle-insensitive properties are demonstrated. This proposed absorber has potential applications in optical switching, electromagnetic stealth, and sensing applications.
In our work, the temperature sensing properties and intrinsic mechanism based on a bismuth–erbium co-doped optical fiber (BEDF) were explored. Through temperature sensing experiments, we found that when the 980-nm pump laser was used, the fluorescence intensity ratio (FIR) at 1560 and 1435 nm showed a good linear relationship at different temperatures and its sensitivity reached 0.1151 dB/°C, the accuracy was 0.2°C, and the R2 of the FIR curve is about 0.9923. At the same time, we also proposed a detection algorithm to judge the working state of the sensor. By changing the BEDF coating material while the fiber is being fabricated, the temperature measurement range can be further improved. The optical fiber temperature sensor will have a broader range of applications.
We propose a fiber optical cell catapult that is bird beak-shaped fiber cone optical tweezers that trap cells, then push them to the fiber tip via the evanescent fields on the side surface of the fiber cone, and finally eject them in a particular direction. The intensity distribution of the light field and the optical force of the fiber catapult are calculated by the finite element method. Moreover, an experimental study of the fiber catapult is given using yeast cells.
In this paper, a surface plasmon resonance (SPR) optical fiber sensor based on graphene coated gold nanotubes is designed in the visible region. A section of optical fiber is taken, the bare core of the cladding layer is polished, and a layer of gold nanotubes is laid on the surface of the core. Graphene is coated on the gold nanotubes to enhance sensor’s sensitivity because it can stably adsorb biomolecules and increase the propagation constant of surface plasmon polariton (SPP).By using wavelength demodulation method and finite element method (FEM), the sensing performance can be improved by optimizing the structural parameters and the number of graphene layers. When the graphene coating N = 2, the maximum sensitivity of the sensor reaches 6000nm / RIU, and the quality factor (FOM) is 152RIU−1. This study provides a potential application prospect for the design of a new generation of high sensitivity biosensors.
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.
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