Two kinds of novel plasmonic high-sensitivity of refractive index(RI) sensors based on analyte-filled photonic crystal fiber (AF-PCF) are proposed in this paper. The metallic gold and silver is used as the surface plasmon resonance (SPR) activity metal. A full-vector finite element method (FEM) is applied to analyze and investigate the sensing and coupling characteristics of this designed AF-PCF with the gold or silver layer. Phase matching between 2nd surface plasmon polariton (SPP) and fundamental modes can be met at different wavelengths as the analyte of RI is increased from 1.40 to 1.42. The phase matching wavelength of the designed AF-PCF with the gold layer is shifted to the longer wavelength direction compared to that with the silver layer, and the resonance strength is much stronger. The average sensitivities of 7040 nm/RIU and 7017 nm/RIU in the sensing arrange from 1.40 to 1.42 with high linearity are achieved for the designed sensors with the gold and silver layers, respectively, which are almost the same. While the figure of merit (FOM) with silver layer is much better than that with the gold layer.Index Terms: Photonic crystal fiber, Surface plasmon resonance. Refractive index sensor 1943-0655 (c)
Terahertz technology has attracted wide attention because of its potential applications in diverse fields, such as spectroscopy, imaging, and nondestructive evaluation, but the lack of functional devices, including polarization convertors, is still a major hurdle for these applications. In previous studies on metamaterialbased polarization convertors, only one single polarization conversion is generally achieved. This paper presents a transmissive dual-functional terahertz waveplate based on an all-dielectric metamaterial composed of periodic subwavelength pillars made of pure silicon that can achieve two different polarization conversions (i.e., a combination of quarter-and half-waveplates) at the same operation frequency and for x-and y-polarized incidences, respectively. Theoretical and numerical analyses are provided to illustrate the design principle. A sample is fabricated and characterized, and the experimental results show that the two polarization conversions are obtained at 1.01 THz, which is in good agreement with the corresponding simulations. Such a dual-functional terahertz waveplate will find applications in terahertz systems and the design strategy can be extended to other frequency ranges as well.
We propose a modified design for a photonic crystal fiber (PCF) filter based on surface plasmon resonance(SPR). The air holes are arrayed in rectangular lattices, while the size and the pitches of holes around the gold-coated holes are different. That can separate the x-polarization and y-polarization of second-order surface plasmon polariton (SPP). The resonance strength of the surface plasmon mode and import of structural parameters of the PCF on the filter characteristics are studied through using the finite element method (FEM). Numerical simulations demonstrate that the thickness of the gold layer, the gold-coated or gold-filled, and the asymmetry around the gold-coated holes have a great effect on the filter characteristics. It is certain to obtain a resonance strength as high as 873 and 771.5 dB/cm at the communication wavelength of 1050 and 1310 nm in x-polarization by adjusting the size and the place of the gold-coated holes, while the loss is extremely low in y-polarization.
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