In this paper, an asymmetric large-mode-area photonic crystal fiber (LMA-PCF) with low bending loss at a smaller bending radius is designed. The finite-element method with a perfectly matched layer boundary is used to analyze the performance of the PCF. To achieve LMA-PCF with low bending loss, the air holes with double lattice constants and different sizes at the core are designed. Numerical results show that this structure can achieve low bending loss and LMA with a smaller bending radius at the wavelength of 1.55 μm. The effective mode area of the fundamental mode is larger than 1000  μm when the bending radius is ≥10  cm. The bending loss of the fundamental mode is just 0.0113 dB/m, and the difference between the fundamental and high-order modes of the bending loss is larger than 10 when the bending radius is 10 cm. Simulation results show this novel PCF can achieve LMA and have effective single-mode operation when the bending orientation angle ranges in ±110°. This novel photonic crystal has potential application in high-power fiber lasers.

the interaction between light and matter, has attracted intensive research interest, due to its potential applications in water electrolysis, [1a] biosensors, [2] photochemical catalysis, [3] and optical heating. [4] LSPR modes are the collective oscillations of conduction band electrons at the interface between materials with negative and positive permittivity, [5] such as Au, [6] Ag, [5c] and Cu, [7] upon illumination with light of specific wavelengths. The electromagnetic field at the surface of the metals is amplified by the electron oscillations. [8] Such near field enhancement affords higher energy electrons, and therefore significantly promote the catalytic performance of the plasmonic metals. [9] The LSPR effect is highly dependent upon the physiochemical properties of the catalysts, such as morphology of the plasmonic metals and the localized electronic landscape. [7,10] Effective utilization of the LSPR effect for high-performance catalysis is require fine tuning of dielectric relaxation routes between the excited plasmonic metals and the surrounding substances. [11] For instance, when the plasmonic metals are nanosized (<30 nm), the LSPR decay would favor chemical transformation, as a result of nonthermalized charge-carriers distributing according to the Landau damping model. [12] So far, enormous efforts have been devoted to controlling the plasmon decay by designing distinctive plasmonic metal-containing nanostructures. [11a,13] Au nanoparticles (NPs) have been frequently studied as typical plasmonic metal catalysts. [5b,14] The deposition of Au NPs onto Ni(OH) 2 nanosheets promoted electrochemical water oxidation under illumination, compared to bare Ni(OH) 2 and bare Au NPs. [1a] Additionally, yolkshell nanostructures (YSs) and core-shell nanostructures (CSs) possess the advantage of collection of radiative, energetic carriers at the shells from the high concentration of electron-hole pairs at the cores, and thus facilitate the charge transfer of the nanomaterials to the adsorbates. [8a,9a,b,e,15] Energy losses within the CSs can be minimized by weakening the scattering, and thus, the confinement of the illumination energy by LSPR can be maximized. The controllable dielectric relaxation of LSPR decay of YSs has been observed in Ag@Pt CSs nanostructures under wavelength-specific illumination. [15b] However, the energy transfer mechanism between the core/yolk and the shell in YSs is still unclear.In this work, hybrid YSs with Au yolk (ca. 8 nm) and Ni 3 S 2 shell (ca. 8 nm in thickness) were fabricated to promote the visible-light-assisted OER. The efficient harvesting of solar energy Hybrid nanostructures with a plasmonic core and catalytic shell often show significantly enhanced catalytic efficiency under illumination of specific frequency. Excitation of localized surface plasmonic resonance on plasmonic metals under illumination can generate hot electrons that assist in the catalytic reaction. However, the correlation between the microstructural geometry, dielectric environment, internal e...

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In this work, a novel design of a high birefringence photonic crystal fiber (HB-PCF) with multimode and low confinement loss is proposed. To achieve high birefringence, the core is designed as an elliptical region, which is enclosed by twelve small holes. Based on this design, replacing the two circular holes at the top and bottom of the core region with two elliptical holes can further improve the birefringence. At the wavelength of 1.55 μm, the birefringence of the fundamental mode (LP) and the second-order mode (LP) are 1.70×10 and 1.85×10, respectively. Meanwhile, the confinement losses maintain on orders of 1×10 dB/km (LP) and 1×10 dB/km (LP). After the effective refractive indices of two types of the proposed HB-PCF are calculated by the finite element method, the birefringence, confinement loss, bending loss, dispersion, and nonlinear coefficient are studied. These results reveal that the HB-PCF might be applied for polarization-maintaining and nonlinear optics.

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