Gold Coated VO2 Nanogratings Based Plasmonic Switches

This paper presents 2 dimensional (2D) and 1 dimensional (1D) gold (Au) coated VO2 (Vanadium Dioxide) nanogratings based tunable plasmonic switch. VO2 is a phase changing material and hence exhibits phase transition from semiconductor to metallic phase approximately at 67 ºC or 340 K (critical temperature) which can be achieved by exposure to IR radiation, application of voltage, heating, etc. and there is a huge contrast between optical properties of its metallic and insulating phases and hence that can be utilized to implement VO2 based optical switches. These VO2 based gratings couple the incident optical radiation to plasmonic waveguide modes which in turn leads to high electromagnetic field enhancement in the gaps between the nanogratings. The proposed Au coated VO2 nanogratings can be fabricated by using current state of art fabrication techniques and provides switchability of the order of femtoseconds. Hence the optical switching explained in our paper can be used fast switching applications. For an optimum switch our aim is to maximize its differential reflectance spectra between the 2 states of VO2, i.e., metallic and semiconductor phases. Rigorous Coupled Wave Analysis (RCWA) reveals that wavelengths for maximum differential reflectance can be optimized over a large spectral regime by varying various parameters of nanogratings for example groove height (h), width (w), gap (g) between the gratings, and thickness (t) of Au coating over VO2 by simulation using RCWA for maximum differential reflectance between VO2 metal and semiconductor phase, i.e., the switching wavelengths can be tuned by varying grating parameters and thus we can have optimum optical switch.

Perpendicular-Spin-Transfer-Torque Magnetic-Tunnel-Junction Neuron for Spiking Neural Networks Depending on the Nanoscale Grain Size of the MgO Tunnelling Barrier

Unlike conventional neuromorphic chips fabricated with C-MOSFETs and capacitors, those utilizing p-STT MTJ neuron devices can achieve fast switching (on the order of several tens of nanoseconds) and extremely low...

Performance analysis of all optical 2 × 1 multiplexer in 2D photonic crystal structure

In optical processing systems, multiplexer is used to design optical devices such as arithmetic logic unit (ALU) and shift register (SR). Through this paper, we investigate the application of nonlinear photonic crystal ring resonator (PhCRR) based on nonlinear Kerr effect for realizing an all optical 2 × 1 multiplexer. The structure consists of two PhCRRs and five optical waveguides using hexagonal lattice silicon (Si) rods with a background of air. Performance of all optical 2 × 1 multiplexer is replicated with the help of finite difference time domain (FDTD) procedure at a wavelength of 1571 nm, and simulations presented an ultra-compact optical structure with ultra-fast switching speed.

Nanocavity-Mediated Fast Magnetic Vortex Core In-Situ Switching by Local Magnetic Field

Fast in situ switching of magnetic vortex core in a ferromagnetic nanodisk assisted by a nanocavity, with diameter comparable to the dimension of a vortex core, is systematically investigated by changing the strength as well as the diameter of the effective circular region of the applied magnetic field. By applying a local magnetic field within a small area at the nanodisk center, fast switching time of about 35 ps is achieved with relatively low field strength (70 mT) which is beneficial for fast data reading and writing. The reason for this phenomenon is that the magnetic spins around the nanocavity is aligned along the cavity wall due to the shape anisotropy when the perpendicular field is applied, which deepens the dip around the vortex core, and thus facilitates the vortex core switching.

Tuning the switching pressure in square lattice coordination networks by metal cation substitution

Coordination networks that undergo guest-induced switching between “closed” nonporous and “open” porous phases are of increasing interest as the resulting stepped sorption isotherms can offer exceptional working capacities for gas storage applications. For practical utility, the gate ad/desorption pressures (Pga/Pgd) must lie between the storage (Pst) and delivery (Pde) pressures and there must be fast switching kinetics. Herein we study the effect of metal cation substitution on the switching pressure of a family of square lattice coordination networks [M(4,4’-bipyridine)2(NCS)]n (sql-1-M-NCS, M = Fe, Co and Ni) with respect to CO2 sorption. The Clausius-Clapeyron equation was used to correlate Pga/Pgd and temperature. At 298 K, Pga/Pgd values were found to vary from 31.6/26.7 bar (M = Fe) to 26.7/20.9 bar (M = Co) and 18.5/14.6 bar (M = Ni). The switching event occurs within 10 minutes as verified by dynamic CO2 sorption tests. In addition, in situ synchrotron PXRD and molecular simulations provided structural insight into the observed switching event, which we attribute to layer expansion of sql-1-M-NCS via intercalation and inclusion of CO2 molecules. This study could pave the way for rational control over Pga/Pgd in switching adsorbent layered materials and enhance their potential utility in gas storage applications.

All-optical frequency-encoded Toffoli gate

The construction of an all-optical frequency-encoded Toffoli gate employing a reflecting semiconductor optical amplifier (RSOA) is proposed in this article. By establishing fields such as quantum computing, optical quantum computing, quantum-dot cellular automata, and superconducting flux logic family, quantum gates have been proved to perform reliably in the present day. A nonzero-mass electron, on the other hand, moves far slower than a quantum particle with zero rest mass, such as a photon. Photons can also be utilized to store data while being sent. These photon qualities have motivated researchers to create quantum gates in the all-optical domain based on them. The RSOA-based implementation of the Toffoli gate gives a significant improvement in the case of high speed, low power, and fast switching time. MATLAB Simulink (R2018a) software is used to simulate the devised design. The theoretical prediction is satisfied by the simulation results.

Phase Diagram and Order Reconstruction Modeling for Nematics in Asymmetric π-Cells

Intense electric fields applied to an asymmetric π-cell containing a nematic liquid crystal subjected to strong mechanical stresses induce distortions that are relaxed through a fast-switching mechanism: the order reconstruction transition. Topologically different nematic textures are connected by such a mechanism that is spatially driven by the intensity of the applied electric fields and by the anchoring angles of the nematic molecules on the confining plates of the cell. Using the finite element method, we implemented the moving mesh partial differential equation numerical technique, and we simulated the nematic evolution inside the cell in the context of the Landau–de Gennes order tensor theory. The order dynamics have been well captured, putting in evidence the possible existence of a metastable biaxial state, and a phase diagram of the nematic texture has been built, therefore confirming the appropriateness of the used technique for the study of this type of problem.