In this work, two-dimensional graphene oxide (GO) (e.g., oxygenated graphene sheets with epoxy, hydroxyl, and carboxyl groups) was reduced to zero-dimensional Br-doped GO quantum dots (Br-GODs) using a one-step method. The GO, which exhibits poor electrical conductivity, was reduced to Br-GODs using hydrobromic acid as a bromine source and reducing agent during hydrothermal reaction. The morphology, structural and photoelectric properties of GO and Br- GODs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible near infrared (UV-Vis-NIR) absorption spectroscopy, photoluminescence (PL), photoluminescence emission (PLE), Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). A photodetector based on Br-GODs material, consisting of interdigitated electrodes, was prepared. The responsivity (R) and detectivity (D*) of the photodetector can reach a maximum of 0.54 A/W and 4.33 × 1013 Jones, respectively, under 850 nm illumination.
A D-shaped photonic crystal fiber (PCF) low refractive index (RI) sensor based on surface plasmon resonance (SPR) is proposed, and its properties are investigated by the finite element method. Gold is selected as the plasmonic material and coated on the open-ring structure to excite the plasmonic modes. The simulation results indicate that the sensor can detect the RI in the range of 1.00 to 1.29, which is a fairly wide detection range in the detection field of SPR-based PCF low RI sensors. When the analyte of the RI varies from 1.28 to 1.29, the maximum sensitivity of 10,000 nm / RIU and the corresponding resolution of 1 × 10 − 5 RIU are obtained in the wavelength range of 1.6 to 2.4 μm. When the RI of the analyte changes from 1.00 to 1.29, the relationship curve between the RI and the resonance wavelength fits well, and the adjusted R2 value is 0.99609. Furthermore, the sensor achieves the figure of merit of 56.98 RIU − 1 and an amplitude sensitivity of 82.76 RIU − 1, respectively. Therefore, the designed sensor can be effectively applied to low RI detection, having a certain commercial potential in medical detection, organic chemistry detections, and related applications.
The evolution properties and the spectral degree of coherence of a partially coherent multi-Gaussian Schell-model vortex (MGSMv) beam propagating in uniaxial crystals orthogonal to the optical axis are studied. Propagation expression for the cross-spectral density and the average intensity of the partially coherent MGSMv beam propagating in uniaxial crystals are derived. Some analyses are illustrated by numerical examples related to the propagation properties and coherence vortices of the partially coherent MGSMv beam in uniaxial crystals. Numerical results show that, upon propagating in uniaxial crystals, the partially coherent MGSMv beam loses its initial dark center distribution. After propagating for sufficient distances, the partially coherent MGSMv beam will also evolve into a flat-topped beam. The evolution behavior of average intensity and coherent vortices depends on the crystal including the ratio of extraordinary and ordinary refractive indices, and beam parameters including the spatial correlation length and topological charge of the beams, as well as the propagation distance.
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