查看更多>>摘要：Nitrogen-vacancy center in diamond based photonic structures are appealing in the field of quantum technology as they offer single photon emission with an efficient directional output beam. In this paper, we report a nano-range waveguide design which is capable of producing -70% photon collection efficiency with a NA of 1. We have utilized the pyramidal diamond structure onto a rectangular diamond substrate with the NV center positioned on top surface of this optical structure. A stable and directional emission of a far field pattern is achieved even with a wide range of dipole positions. Less power coupling inside the optimized device helps to enhance the efficiency near NV emission spectra. This optical waveguide can be employed in various applications in the NV based magnetometers and quantum devices
查看更多>>摘要：Large angle of incidence and multi-band are the goals pursued by modern multilayer diffractive optical element (MLDOE). The polychromatic integral diffraction efficiency (PIDE) is sensitive to the incident angle and refractive index of the substrate material. Therefore, we propose a new solution for selecting a set of optimal substrate materials of MLDOE to obtain the maximum PIDE in a large angle incidence. A mathematical model is established and the substrate material selection method based on comprehensive PIDE difference comparison (SMS-CPDC) for dual-band MLDOE is proposed. The three-layer DOEs in visible-NIR dual-band and the double-layer DOEs in MWIR-LWIR dual-band are designed and discussed as the examples. In visible-NIR dual-band and MWIR-LWIR dual-band, the optimal substrate material combinations are N-PK52A-PC-P-SF69 and ZNSE-ZNS, respectively. When the comprehensive PIDE decreases to 90%, the available incident angle range is +/- 51.6 degrees for N-PK52A-PC-P-SF69 MLDOE and that is +/- 10.9 degrees for ZNSE-ZNS MLDOE; When the comprehensive PIDE decreases to 85%, the available incident angle range is +/- 54.2 degrees for N-PK52A-PC-P-SF69 MLDOE and that is is +/- 12.1 degrees for ZNSE-ZNS MLDOE. The results are of great significance for the application of MLDOEs in hybrid system with a large range of incident angle and multi operating band.
查看更多>>摘要：The PANDA segmented ring-core (SERC) few-mode fiber (FMF) can further enhance its characteristic of separating the eigenmodes by dividing the RC into several ring-sectors (RSs) with variable angles and decreasing refractive indices in the azimuthal direction. The novel PANDA SERC FMF with an appropriate choice of parameters can support 10 fully separated eigenmodes, where minimum effective index differences min(Delta n(eff)) between adjacent eigenmodes can reach 3.5 x 10(-4) over the whole C + L band. Moreover, the group velocity dispersion (GVD), effective mode areas and losses of the fiber are within the range of (-42, 20) ps/nm/km, (31, 75) mu m(2) and (0.4, 0.56) dB/km over the whole C + L band. Numerical results show that the designed fiber has excellent bending resistance, while the splice losses between standard step-index fiber and PANDA SERC FMF are within the range of 0.62-1.05 dB at 1550 nm. Consequently, the proposed fiber can provide a promising way to design the fully degeneracy-lifted polarization-maintaining (PM) FMF for the mode-division multiplexing (MDM) transmission.
查看更多>>摘要：A numerical study has been performed on electric field profile features of photonic nanojet generated by a SiO2 microcylinder with a varied diameter. The study shows that a strong (44.2I(0)) nanojet with 0.7 lambda lateral width and 7.8 lambda length can be obtained, which, as a line light source, has a potential for application in fields of nanopatterning and nanolithography. Along with the study on a single-layer microcylinder, we further studied the characteristics of the nanojet generated by a two-layer microsphere consisted of an interior LiNbO3 microsphere and an exterior semiconductor layer, which have refractive indices of 2.34 and similar to 3.3 @ 500 nm, respectively. The study focuses on nanojet generation condition and the effects of refractive indices of microsphere materials and background, and working wavelength on electric field distribution characteristics of the nanojet. By immersing the two-layer microsphere into a proper liquid such as the deionized water, an ultra-long (>14 lambda), ultra-strong (>50I(0)) and narrow enough (0.56 lambda) nanojet could be created. All of the characteristics and effects are qualitatively interpreted in terms of ray optics in combination with Mie scattering theory.
查看更多>>摘要：This paper intends to investigate the modulational instability (MI) criterion of two core positive negative index coupler channel setup from the obtained analytical dispersion relation for MI gain profile. The governing equation, the modified nonlinear Schrodinger equation (MNLSE) is studied for the role of higher order dispersion (HOD) and higher order nonlinearity (HON) on instability spectra of two core positive indexed coupler (PIM) and negative indexed coupler (NIM) arrangement. The HOD comprises of the second, third, fourth and fifth order linear dispersion terms and HON is inclusive of cubic, quintic, septic, cubic-quintic-septic-self-steepening (SS), and cubic-quintic-septic-intrapulse Raman scattering (IRS). Our study reveals that it is the 6th order linear dispersion term which brings in the considerable changes of MI gain spectrum in both normal and anomalous dispersion regimes. In particular, the combined effect of septic SS and IRS in two core directional coupler with NIM channel proves to be very crucial in the generation of instability gain spectra. This study has higher prospects in generation of solitary wave in two core directional system for optical fiber communication.
查看更多>>摘要：Isopropyl alcohol (IPA) is commonly used for process cleaning. Expensive chemical filters are installed in cleanrooms to remove high concentrations of IPA contamination. We firstly use organic acid to modify coal-based activated carbon (AC) as a starting point for preparation of filtration media for IPA removal. AC was characterized before and after this modification using BET, SEM, thermogravimetric analysis (TGA), FTIR, and temperature programmed decomposition (TPD), comparing results with those obtained from the same tests applied to commercial coconut AC. These tests found that the specific surface area of coal-based AC, modified by the oxalic acid, was not as large as that of commercial AC, but there was a significant increase in surface area following surface modification. As can be seen from the SEM images, following modification, the surface roughness of the AC increases, with additional precipitation of oxalic acid particles. Be-sides the deposition of oxalic acid functional groups on the AC surface, modification also reduces the presence of basic groups and increases the number of acidic groups, as quantified by TPD with TGA. The adsorption isotherms of IPA adsorption are well fitted by both Langmuir and Freundlich isotherm models. Breakthrough times of 590, 413, and 380 days were observed for modified coal-based AC at 1 ppb initial IPA concentration and 0.3, 0.4, and 0.5 m s(-1) face velocity, respectively. The adsorption kinetics are best described by a Pseudo-Second order kinetics model and also could be predicted by the intraparticle diffusion and membrane diffusion models.
查看更多>>摘要：The presented work deals with the investigation of Biswas-Arshed model which has great importance in the theory of solitons. The proficient approach, namely, modified auxiliary equation (MAE) method is practiced. This method provides results in the form of hyperbolic, trigonometric and rational functions. The dynamical behavior of obtained results is observed through graphs by assigning particular values to free parameters.
查看更多>>摘要：We propose a compact multilayer thin film color pixel and a method for efficient transmissive color in the visible regime. When the angle of incidence (AOI) varies between 0 and 60, there is almost no change of the transmitted color. Meanwhile, additional dielectric layers at the top and bottom of the hybrid structure work as anti-reflection (AR) layers, which greatly improve the transmission efficiency. The performance can be switched by adjusting the thickness of the film, as well as controlling the charge carrier concentration in a doped indium-gallium-zinc-oxide (IGZO). Besides their simple, large scale compatible, and electron beam lithography (EBL) free fabrication route, the designed structure provides relatively high efficiency, high color purity, and low crosstalk, which may provide some new insights for structural color applications.
查看更多>>摘要：We have manufactured an optical ridge waveguide in ZnSe crystal utilizing techniques of C5+ ion irradiation and precise diamond blade dicing. From near-infrared to mid-infrared band, the waveguide supports single-mode transmission and the propagation losses have been reduced as low as 0.8 dB/cm (lambda = 1.064 mu m), 0.6 dB/cm (lambda = 2.2 mu m) and 0.4 dB/cm (lambda = 4 mu m) after a series of annealing treatments. The refractive index profile of the waveguide is reconstructed and the simulated near-field modal profile fits well with the experiment. The Raman spectrum of the waveguide and substrate indicates there is no large lattice damage after C5+ ion irradiation.
查看更多>>摘要：In order to enhance the strength of steel / aluminum welded joints, the alloying effect of Cu and Ni on the Fe / Al interface was studied by establishing the Fe/Al interface model by using the first principle method of density functional theory. The energy, heat of formation, density of states, electron population and fracture energy of the system were calculated. On this basis, the experiments of steel/aluminum laser welding with preset Cu and Ni foil were carried out. The results show that Cu and Ni preferentially replace the Fe atoms in the Fe/Al interface, and the stability of the alloy system increases. Alloying improves the bonding electron number and electron transfer number of the Fe/Al interface system, enhances the bonding effect of the Fe/Al interface, and improves the bonding strength of the Fe/Al interface. Among them, nickel can significantly increase the bonding strength of Fe/Al interface. At the same time, the tensile test shows that the average tensile strength of steel/aluminum welded joint is 39 MPa and the elongation is 0.81%. After adding copper foil, the average tensile strength and elongation of welded joints increased by 38.5% and 113.58%. After adding nickel foil, the average tensile strength and elongation of welded joints increased by 100% and 179%. The alloying effect of Ni greatly improves the strength and toughness of steel/aluminum welded joints. It provides practical reference and theoretical guidance for steel/aluminum welding.
NSTL
Elsevier