Design Of All-optical Switches Research Articles

Compact and efficient PC-based directional coupler all-optical switch

Abstract Recently, the photonic crystal–based optical components and devices have attracted many researchers’ attention because of its nanoscale size which makes it suitable for the photonic integrated applications. Hence, the design of all-optical switch based on photonic crystal structure have been investigated in the past few decades to meet the requirement of ultracompact size with optimized performances such as fast response time, high extinction ratio with low insertion loss. Here, the design of directional coupler–based all-optical switch operating at the wavelength of 1550 nm is proposed with new design values. The resonant operating wavelength of the switch is identified with the help of finite element method. Then, the cross-state switching operation is analysed with the help of finite-difference time-domain method by applying a nonlinear optical Kerr effect switching mechanism. The important performance metrics of the proposed design such as insertion loss, extinction ratio, directivity and the response time are obtained as −0.008 , 26.98, 20.44 dB and 0.13ps, respectively. The total footprint of the proposed optical switch is approximately 128 µm2.

Plasmonic all-optical switching based on metamaterial/metal waveguides with local nonlinearity

We present a plasmonic all-optical switch based on Mach–Zehnder interferometer (MZI) with local nonlinearity. The design of the miniaturized all-optical switch is possible by employing surface-plasmon polaritons (SPPs) that confine the energy of electromagnetic (EM) waves at sub-wavelength scale. The coupling between sub-wavelength plasmonic waveguides in MZI and a control beam generates ‘ON’ and ‘OFF’ states at the switch and switching between ‘ON’ and ‘OFF’ states happens when the control beam is turned on or off. The waveguides cladding in the switch structure is made of lossy media including metamaterials with positive and negative EM susceptibilities and metals; the core consists of nonlinear and dielectric media. Employing materials with negative EM susceptibilities in the switch structure facilitates the propagation of both transverse electric and transverse magnetic SPPs along the waveguides. Our all-optical switch design enables multi-frequency switching with low-intensity control field. Ascertaining the capabilities of multi-frequency plasmonic all-optical switches facilities their applications in miniaturized photonic circuits and in biosensors.

In brief

PAGE 192 Researchers in the USA propose a two-dimensional pixelating technique for actuating liquid metal. Continuous electrowetting is used to move the liquid metal between reservoirs, which resulted in ON and OFF switching of adjacent pixels. This method removes the need for a physical switch to be employed in pixelated antennas. PAGE 227 An indoor positioning method based on a single LED and camera is given in work from China. By simultaneously measuring both the strength and the angle of arrival of the LED light, ‘fingerprint’ signals of the receiver position are identified. This work is proposed as an optimum solution for indoor positioning systems using optical communication. Liquid metal actuation between pixels using continuous electrowetting. PAGE 229 Work from Iran presents a low power, all-optical switch consisting of a microfibre loop resonator in one arm of a microfibre Mach–Zehnder interferometer. The design is numerically predicted to offer easy configuration, small dimensions, low threshold power and fast switching times in optical signal processing and communications applications. A single camera and LED are used to determine receiver positions indoors. PAGE 194 Researchers in Egypt are developing an accumulated grey level image (AGLI) method for lung cancer detection. The method works by classifying genetic mutations in DNA sequences of effective genes in lung cancer, using a combination of principal component analysis and AGLI. The reported computational approach could be used as a diagnostic aid to classify genetic mutations associated with lung cancer. Numerical predictions propose an efficient all-optical switch design for optical communication applications. PAGE 187 A simple polarisation reconfigurable printed monopole antenna is presented by researchers in China. The antenna structure consists of a printed monopole, two switching circuits, and a reflector, and is shown to have four operational states that are accessed by controlling the ON/OFF states of the switching circuits. The antenna is a candidate for use in multi-frequency and multi-polarisation systems. A computational diagnostic approach for identifying genetic mutations associated with lung cancer. Four operational states reported for a simple polarisation reconfigurable printed monopole antenna.

A scheme for high-quality nonlinear all-optical switches

The weak material nonlinearity and the high precision requirement for high-quality resonances are the two most critical hurdles in the design of all-optical switches. It is shown that, when the guided-mode has a very small wave vector component normal to the guiding layer, the guided-mode resonance (GMR) is robust against the structure parameters. Meanwhile, the corresponding GMR is very sensitive to the modulations of both the incident wavelength and the permittivity of the guiding layer. The GMR then features easy-control, high-quality and permittivity-sensitive. Based on such configuration, low-threshold all-optical switches working between zero- and total-transmission are realized.

Light Switched Off by Weaker Beam

An all-optical switch design uses an asymmetric waveguide that reduces the beam power requirements, which is essential for making such devices practical.

Intensity–intensity and intensity–amplitude correlation of microwave photons from a superconducting artificial atom

We investigate the dynamics of the microwave-frequency nonclassical correlations in a three-level -configuration artificial atom, which is realized by superconducting quantum circuits. The intensity–intensity correlation and intensity field are strongly dependent on the relative phase of the driven fields. It is found that two interference loops are formed in the dressed state picture at or π, which are responsible for the generation of nonclassical microwave photons. When the phase is changed into or , the temporal correlation functions exhibit different oscillating behaviors. The phase-sensitive nonclassical correlations of fluorescence photons may find practical application in the design of all-optical switches and quantum information processing.

V-shaped dark solitons in inhomogeneous optical fibers

Soliton control offers novel conceptual opportunities for all-optical shaping, switching and routing of optical signals encoded in soliton formats. In this paper, V-shaped dark solitons propagation in inhomogeneous optical fibers are investigated to carry out soliton control. Analytic dark soliton solutions for the variable coefficient nonlinear Schrödinger equation are obtained with the Hirota method. The group velocity dispersion coefficient of inhomogeneous optical fibers is chosen to be the tanh function, and the influences of corresponding parameters are analyzed. Results might be of potential applications in the design of all optical switches and pulse signal converters in ultra-fast optics.

An optimization procedure for the design of all-optical switches based on metal-dielectric nanocomposites.

We present a procedure to optimize the performance of all-optical switches based on metal-dielectric nanocomposites. The management of constructive and destructive interference between the third-, fifth- and seventh-order susceptibilities allowed characterization of optimal conditions for ultrafast switching with reduced losses. Proof-of-principle experiments with metal-colloids are reported to validate the method.

Enhanced Cross-Phase Modulation via Phase Control in a Quantum dot Nanostructure

A four-level quantum dot (QD) nanostructure interacting with four fields (two weak near-infrared (NIR) pulses and two control fields) forms the well-known double-cascade configuration. We investigate the cross-phase modulation (XPM) between the two NIR pulses. The results show, in such a closed-loop scheme, that the XPM can be greatly enhanced, while the linear absorption and two-photon absorption (gain) can be efficiently depressed by tuning the relative phase among the applied fields. This protocol may have potential applications in NIR all-optical switch design and quantum information processing with the solid-state materials.

Ultrafast all-optical switching based on cross modulation utilizing intersubband transitions in InGaAs/AlAs/AlAsSb coupled quantum wells with DFB grating waveguides

A distributed feedback Bragg grating waveguide all-optical switch design relying on the ultrafast cross modulation effect of the intersubband transitions in InGaAs/AlAs/AlAsSb coupled double quantum wells is demonstrated. The pump-induced phase modulation to the signal light is converted to intensity modulation efficiently on chip with the help of the grating structures. To our best knowledge, the switching dynamic characteristics of such design are reported for the first time. With a 400 μm long grating waveguide, 3 dB modulation depth with switching energy of 5.5 pJ and recovery time of 4.5 ps is obtained for the switch-off operation.

Polarization qubit phase gate between two far-infrared pulses in three-coupled quantum wells

The cross-Kerr nonlinearity arising between two far-infrared (FIR) pulses is investigated in a three-coupled-quantum-well (TCQW) structure based on intersubband transitions. The results show that the giant Kerr nonlinearity with a relatively large cross-phase-modulation phase shift can be used for realizing polarization quantum phase gate in this TCQW structure. Such a semiconductor system is much more practical than its atomic counterpart because of its flexible design and the wide tunable parameters. This protocol may have potential applications in FIR all-optical switch design and quantum information processing with solid-state materials.

All-optical switch based on photonic crystal microcavity with multi-resonant modes

We present a design of all-optical switches based on one-dimensional photonic crystals (1D PhC) doped with nonlinear optical materials. The 1D PhC switch structure is composed of a PhC cavity sandwiched by two accessional PhC microcavities. The center PhC cavity has two resonant frequencies with nearly the same quality factors ( Q), while the accessional PhC cavities have the same resonant frequency, which is equal to one of the resonant frequencies of the center cavity. The two accessional PhC cavities cause reduction of Q value in this resonant frequency and result in different Q values of two modes. We realize all-optical switch effect by selecting pump light wavelength at the low Q mode and probe light wavelength at the other mode. The theoretical simulations by using the finite difference time domain method show that the pump light intensity required to realize optical switch effect in the designed switch is 50 times smaller than that in one-dimensional photonic crystals cavity with only one resonant mode.

Nonlinear Optical Switch Utilizing Long-Range Surface Plasmon Polaritons

We present a detailed study of the directional couplers (DCs) based on nanometer-thin and micrometer-wide Ag stripes embedded in nonlinear material. A novel design of all-optical switch based on nonlinear plasma waveguide couplers is proposed. The critical optical power Pc of nonlinear optical switch is low, and the switch effect is easy to be observed. The LR-SPP optical switch has been investigated at λ = 0.633 μm, 1 μm, 1.55 μm, demonstrating the feasibility of LR-SPP-based all-optical switches for operation in the very broad wavelength range. All the simulations in this paper were performed by using rigorous numerical schemes based on the full-vector finite-element method.

Design of all-optical switches based on carrier injection in Si/SiO/sub 2/ split-ridge waveguides (SRWs)

All-optical switches based on optical carrier injection in high-index-contrast Si/SiO/sub 2/ split-ridge-waveguide (SRW) couplers are analyzed. The waveguide devices are suitable for the construction of low-loss optical switch matrices as well as fast optical switching. These devices exhibit robustness against fabrication tolerances, improved heat sinking, good carrier confinement, and high uniformity in transmission over the entire C-band of optical communications, in contrast to comparable devices based on buried or ridge waveguides. Reasonably low electrical switching power of 1-10 mW is predicted for switching frequencies of 1 MHz to 1 GHz. Carrier recombination measurements in thin Si layers passivated with different oxide layers confirm the feasibility of the designed switches and modulators.

Interferometric all-optical switches for ultrafast signal processing

All-optical switches find applications in ultrahigh-speed network-user interfaces and in specialized high-speed processors, such as data regenerators and encryptors and microwave signal generators. We describe a semiconductor optical-amplifier-based single-arm interferometric switch called the ultrafast nonlinear interferometer. We discuss how the gain and the refractive-index nonlinearities in semiconductor optical amplifiers have an impact on the all-optical switch design, and we review experimental results obtained with the ultrafast nonlinear interferometer.

Effective non-linear coefficients of optical waveguides

Using the weakly guiding approximation, and with the assumption that the non-linearities are sufficiently weak so as not to change the transverse mode profile, perturbation theory is used to derive simple expressions for evaluating the modal, or effective, non-linear coefficients of optical waveguide structures based on the non-linear coefficients of the constituent materials. In particular, the third-order and fifth-order optical non-linearities of refraction and absorption are discussed. The expressions are used to estimate the effective modal non-linear refraction coefficients for various types of slab waveguides, focusing primarily on femtosecond refractive non-linearities in semiconductor amplifiers, including quantum-well structures. The results are of particular relevance to the design of all-optical switches based on these effects.