查看更多>>摘要：In this study, simulation, analysis, and synthesis of silver plasmonic nanostructures were investigated for use in biomolecule detection. At first, silver nanoparticles (SNPs) were synthesized by a chemical reduction method using polyethylenimine as both a reducing and a stabilizing agent. The SNPs were characterized by UV-visible spectroscopy, dynamic light scattering, and field emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy measurement techniques and showed spherical morphology with an average particle size of 38 nm and a localized surface plasmon resonance (LSPR) peak around 400 nm. The plasmonic effects of the silver nanostructures were also investigated for detection of glucose as a model analyte, with a concentration range of 0.0-2.603 mol/L. Wavelength shifts of 0.033 and 12.04 nm were obtained for glucose concentrations of 0.0039 and 2.603 mol/L, respectively; these shifts yielded the sensitivities of 482.75 and 189.02 nm/RIU and figures of merit (FOMs) of 13.5 and 5.24, respectively. The simulation results indicated the ability of SNPs of 30 nm to detect glucose concentrations as low as 0.0039 mol/L with an LSPR wavelength shift of about 0.033 nm. Also, the sensitivity and FOM were calculated for a 10 x 10 array of non-uniform size nanoparticles according to the experimental sizes. The simulation results revealed the significance of both the nanoparticle size and the particle size uniformity of a realistic array on the sensitivity and LSPR peak shift of SNPs. These findings show that it is possible to use an LSPR-based sensor to detect other biological samples by tuning their plasmonic features.
Heydarian, KhosroNosratpour, ArezRazaghi, Mohammad
11页
查看更多>>摘要：In this study, a high-speed all-optical NAND logic gate (AO-NAND-LG) was designed and numerically simulated. The simulation was performed using the photonic crystal-semiconductor optical amplifier (PC-SOA) structure based on the Mach-Zehnder interferometer and nonlinear cross-phase modulation mechanism. The input optical pulse sequence used in the design was the return-to-zero type. Moreover, two PC-SOAs were utilized in the design of the NAND-LG. The rate and propagation equations were solved using the finite difference method. The optimal mode was achieved for NAND-LG with an energy value of 2.2 fJ for input pulse trains A and B, and an injection current of 1 mA at a bit rate of 80 Gbps. Furthermore, the impacts of the pattern effect, conversion efficiency, extinction ratio, and gain recovery on the design of the AO-NAND-LG were analyzed for the first time in simulations to enhance the performance and efficiency of the PC-SOA. Furthermore, the results demonstrated that the PC-SOA exhibited better logical performance than the ordinary SOA, and it is a suitable candidate for integrated optical circuits because it is much shorter than the SOA.
查看更多>>摘要：The optical properties of dielectric homogeneous nonmagnetic vanadium dioxide (VO2) nanospheres are studied theoretically for a 20 nm diameter in air (n = 1) and for different diameters between 20 and 240 nm in water (n = 1.33). The absorption, scattering and extinction efficiencies are calculated for VO2 nanospheres by using the Metallic Nanoparticle Boundary Element Method (MNPBEM) toolbox. It is calculated the extinction efficiency of a 20 nm diameter VO2 nanosphere in the air for metallic phase. The Localized Surface Plasmon Resonance (LSPR) which looks like in noble metals as predicted is found in the NIR region. The shape and position of a 20 nm diameter VO2 nanosphere's LSPR is discussed in a qualitative manner. The absorption, scattering and extinction efficiencies of the VO2 nanosphere with varying diameters are investigated systemically in water for the metallic phase. The relative contributions of the absorption and scattering efficiencies in the metallic state are discussed to the extinction efficiencies. The results indicated that absorption is the dominant process in the wavelength range of 300-2400 nm. In addition to the LSPR, a Mie Resonance peak was found in the visible region for VO2 nanospheres with diameters bigger than 100 nm. The infrared switching properties of the VO2 nanospheres are investigated by calculated extinction efficiencies with various diameters in water for the metallic and insulating phases. The smart window parameters such as luminous transmittance and solar modulation are discussed in terms of extinction efficiencies of metallic and insulating phases which can be a guide to find the optimum diameter of VO2 nanosphere in application. The LSPR intensity is investigated with varying diameters of the nanospheres at the wavelength at which the LSPR is seen. It is found that the LSPR intensity is almost constant up to 60 nm diameter and decreases rapidly in between 60 and 240 nm diameter of VO2 nanospheres. The size dependency of the LSPR peak of the VO2 nanospheres is also investigated systematically. There is a red-shift from 1096 to 1324 nm in the LSPR peak values and broadening from 760 to 900 nm in the LSPR's FWHM that shows also broadening in LSPR bandwidth while increasing the diameter of VO2 nanosphere from 20 to 240 nm. It is found that the LSPR's peak position changes exponentially with the diameter and FWHM changes almost linearly for the diameter values studied.
查看更多>>摘要：This study introduces the influence of linearly polarized terahertz laser field (TLF) on electronic and anisotropic optical absorption coefficients (OACs) related to the cubical quantum dots (CQDs). The energy levels and wave functions of the system are obtained by solving the Schro center dot dinger equation within the framework of the effective mass. The OACs are inferred from the scheme of compact density-matrix formalism. The results show that the laser correction parameters and polarization angle of TLF have a significant influence on the optical properties. As a key result, the modulation of anisotropic OACs of CQDs by terahertz laser field with different parameters is given.
查看更多>>摘要：A comparative study of plasmon-polariton resonance excited by graphene and different metals in the terahertz range is proposed. The optimum structure is prism/(sample/pomusTa(2)O(5))(7)/sample/plasmon layer/ substrate. The variation of the proposed sensor performance as a function of the thickness of the plasmon layer, thickness of the porous layer, porosity of the porous layer, refractive index of the first layer, thickness of the first layer, and the incident angle with changing the refractive index from 1 to 1.1 using Ag, Al, Au, Cu, and graphene are studied. Under optimum conditions, the proposed sensor has very high performance (sensitivity = 5.5 THz/RIU, figure of merit = 341 RIU-1, and quality factor = 210). The proposed structure can be used in refractive index gas sensors.
NSTL
Elsevier