All-Optical Universal Logic Gates at Nano-scale Dimensions

Though photonics displays an attractive solution to the speed limitation of electronics, decreasing the size of photonic devices is one of the major problems with implementing photonic integrated circuits that are regarded the challenges to produce all-optical computers. Plasmonic can solve these problems, it be a potential solution to fill the gaps in the electronics (large bandwidth and ultra-high speed) and photonics (diffraction limit due to miniaturization size). In this paper, Nano-rings Insulator-Metal-Insulator (IMI) plasmonic waveguides has been used to propose, design, simulate, and perform all-optical universal logic gates (NOR and NAND gates). By using Finite Element Method (FEM), the structure of the proposed plasmonic universal logic gates are designed and numerically simulated by two dimensions (2-D) structure. Silver and Glass materials were chosen to construct proposed structure. The function of the proposed plasmonic NOR and NAND logic gates was achieved by destructive and constructive interferences principle. The performance of the proposed device is measured by three criteria; the transmission, extension ratio, and modulation depth. Numerical simulations show that a transmission threshold (0.3) which allows achieving the proposed plasmonic universal logic gates in one structure at 1550 nm operating wavelength. The properties of this devise was as follows: The transmission exceeds 100% in one state of NAND gate, medium values of Extension Ratio, very high MD values, and very small foot print. In the future, this device will be the access to the nanophotonic integrated circuits and it has regarded fundamental building blocks for all-optical computers.

AlGaN-Based 1.55 µm Phototransistor as a Crucial Building Block for Optical Computers

An optically activated, enhancement mode heterostructure field effect transistor is proposed and analytically studied. A particular feature of this device is its gate region, which is made of a photovoltaic GaN/AlN-based superlattice detector for a wavelength of 1.55 µm. Since the inter-subband transition in this superlattice does normally not interact with TE-polarized (or vertically incoming) radiation, a metallic second-order diffraction grating on the transistor gate results in a re-orientation of the light into the horizontal direction—thus providing the desired TM-polarization. Upon illumination of this gate, efficient inter-subband absorption lifts electrons from the ground to the first excited quantized state. Due to partial screening of the strong internal polarization fields between GaN quantum wells and AlN barriers, this slightly diagonal transition generates an optical rectification voltage. Added to a constant electrical bias, this optically produced gate voltage leads to a noticeable increase of the transistor’s source-drain current. The magnitude of the bias voltage is chosen to result in maximal transconductance. Since such a phototransistor based on high-bandgap material is a device involving only fast majority carriers, very low dark and leakage currents are expected. The most important advantage of such a device, however, is the expected switching speed and, hence, its predicted use as an optical logic gate for photonic computing. In the absence of a p-n-junction and thus of both a carrier-induced space charge region, and the parasitic capacitances resulting thereof, operation frequencies of appropriately designed, sufficiently small phototransistors reaching 100 GHz are envisaged.

Optical Computing: An Introduction

Optical computing is the use of optical systems to perform numerical computations or process information. It is the science of making computing work better using optics and related technologies. Optical computers are computers of the future that use of light particles called photons. They come as a solution of miniaturizing problem. They are the most feasible devices that can replace electronic computers with impressive speeds. This paper provides a brief introduction to optical computing.

Quantum Computing in Four Spatial Dimensions

Relationships among near set theory, shape maps and recent accounts of the Quantum Hall effect pave the way to quantum computations performed in higher dimensions.  We illustrate the operational procedure to build a quantum computer able to detect, assess and quantify a fourth spatial dimension.  We show how, starting from two-dimensional shapes embedded in a 2D topological charge pump, it is feasible to achieve the corresponding four-dimensional shapes, which encompass a larger amount of information.  This novel, relatively straightforward architecture not only permits to increase the amount of available qbits in a fixed volume, but also converges towards a solution to the problem of optical computers, that are not allowed to tackle quantum entanglement through their canonical superposition of electromagnetic waves.