查看更多>>摘要：Gold-silver and silver-gold core-shell nanoparticle dimers were studied based on their extinction cross-section spectrum and bulk refractive index sensitivity. The simulations were performed by using the boundary element method (BEM) and the polarization direction of the used plane-wave excitation was parallel with the symmetry axis. The running parameters were the particles' outer and inner radii and their (interparticle gap/full diameter). For different particle sizes and distances, the shape of the spectra and the refractive index sensitivities are presented. In the extinction spectra, the observable peaks originate from either the gold or silver components and the most intense peak position can be distinctly assigned to one of them. A sharp boundary separates these two regions in the plane of the core radius and shell thickness parameters. It was found that by decreasing the interparticle gap, the boundary line between these two regions shifts towards the thinner shells for Ag@Au dimers, while it shifts towards the smaller cores for Au@Ag dimers. Since the sensitivity of peaks corresponding to the Au and Ag components are significantly different, the presented data can help optimize interparticle gaps concerning the core/shell thicknesses to maximize the sensitivity of nanoparticle dimers.
查看更多>>摘要：A new multifunctional resonant device for THz and far-infrared regions based on surface plasmon-polariton graphene resonator and waveguides is suggested and analyzed in this paper. The device consists of a circular graphene resonator and four nanoribbons serving as waveguides. Every waveguide is front-coupled to the resonator with a small gap between them. The waveguides are oriented with the angle 90 circle between them. The graphene elements are deposited on a dielectric substrate. The Fermi energy of graphene can be dynamically varied by applying an electrical potential difference between the graphene and a thin polysilicon layer which acts as an electrode. The resonator can work with dipole and quadrupole resonant modes. They are used to provide the functions of tunable band-pass filter, tunable power divider and switch. Using the scattering matrix description of the four-port, the circuit theory representation and full-wave analysis, we show that for the central frequency 14.52 THz the parameters of the developed device are as follows: the Q-factor due to use of resonant structure is (6 divided by 8), the matching in the pass-band with return loss of - 17 dB and low insertion loss of about 1.0 dB. The component provides a tunability of the central frequency and the power ratio between the three output ports can be projected in a wide range. In the OFF regime, the transmission coefficients to output ports are lower than - 42 dB.
Ganeev, R. A.Shuklov, I. A.Zvyagin, A. I.Mardini, A....
8页
查看更多>>摘要：We synthesized the colloidal mercury telluride quantum dots (QDs) and analyzed their low-order nonlinear optical properties using 1064 nm and 532 nm, 10 ns pulses. HgTe QDs colloidal suspension showed the strong saturable absorption and negative nonlinear refraction (saturation intensity I-SA = 5 x10(8)W cm(-2), nonlinear absorption coefficients attributed to saturable absorption and reverse saturable absorption beta(SA) =-4 x10(-9)cm W-1 and beta(RSA) = 1 x10-8 cm W-1, nonlinear refractive index gamma =-6 x10(-13) cm(2) W-1) while using the 532 nm probe pulses. The nonlinear optical parameters of this suspension at 1064 nm were smaller (nonlinear absorption coefficient attributed to the two-photon absorption beta(2PA) = 6 x10(-10) cm W-1, gamma =-5 x10(-14) cm(2) W-1). The negative nonlinear refraction of HgTe QDs was attributed to the thermal and Kerr effects in the case of 532 nm and 1064 nm probe pulses, respectively.
查看更多>>摘要：Here we report on a large-scale fabrication and application of triphenylphosphine oxide (Ph3PO) thin films for catalytic nucleophilic substitution of alcohols under modified Appel conditions. We found a relationship between the fabrication conditions and the optical and catalytic properties of the resulting films. An increase in the fabrication temperature along with a decrease in the film thickness makes it possible to obtain both an optically high-quality surface and the most efficient structure for catalysis allowing to achieve 93% yield. The key features of the fabrication method proposed are an operationally simplicity, low catalyst loading up to 10 mol%, medium reaction times, mild conditions, and large-scale application.
Morozov, Mikhail Yu.Popov, Vyacheslav V.Fateev, Denis, V
5页
查看更多>>摘要：Electrical tuning the radiative damping of "nonradiative" (weak) terahertz plasmon mode in a periodic dual grating-gate graphene structure is studied theoretically. Tuning the dc voltage value applied to one of the gate subgratings can change the radiative damping of the weak plasmon mode from zero to the dissipative damping of the plasmons in high-quality graphene allowing for maximum energy conversion from the incident wave to "nonradiative" plasmon mode. Radiative damping increases due to the increase of the dipole moment of this mode by virtue of its asymmetrical gating. Using the weak plasmon modes is important for effective excitation of the plasmon resonances in high-quality graphene as well as for realizing the concept of low-threshold terahertz lasers based on graphene plasmonic structures.Data availability: Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
查看更多>>摘要：As a member of ferromagnetic insulators (FIs), Cr2Ge2Te6 (CGT) was successfully manufactured as an excellent saturable absorber (SA) for demonstrating passively Q-switched erbium-doped fiber laser (EDFL), for the first time. The saturation intensity and modulation depth of CGT SA was 24.98 MW/cm(2) and 14.10%, respectively. The Q-switched operation was stable over the pump power range of 168.2-529.3 mW and its central wavelength was located at 1530.7 nm. The experimental results suggested that the new 2D material CGT was an effective SA for demonstrating passively Q-switched operation.
NSTL
Elsevier