A comparison of optically and electronically controlled optical switches

Electronically and optically controlled optical switches are compared with respect to switch energy requirements. Only switches based on optical phase change are treated, since these have the largest flexibility. Further, only switches that preserve input wavelength at the output are considered, due to cascadeability requirements. It is argued that as long as ‘all-optical’ switches need electronically controlled switches for information transfer to the optical signals controlling the all-optical switch, this will compromise any other advantages that the all-optical switch and the corresponding systems might have. A further application for all-optical switches, which currently are orders of magnitude faster than electronically controlled ones, would be in banks of electronically controlled slower all-optical switches which are all-optically multiplexed to drive all-optical switches to data rates not currently achievable by electronically controlled switches. It is argued that such systems will be complex, requiring sophisticated electronic synchronization and being inferior to corresponding wavelength division multiplexing systems. Power dissipation and switch energy are analyzed for two different physical mechanisms for controllably changing the refractive index in the all-optical and electronically controlled optical switches: Pockels and Kerr effects as well as the plasma or free carrier effect and the relative merits of electronically and optically controlled optical switches using these are discussed. It is shown that, in the former case, (Pockels and Kerr effects) using representative data, electronically controlled switches are generally more power efficient than the all-optical counterparts.     

Optically and thermally induced molecular switching processes at metal surfaces

Using light to control the switching of functional properties of surface-bound species is an attractive strategy for the development of new technologies with possible applications in molecular electronics and functional surfaces and interfaces. Molecular switches are promising systems for such a route, since they possess the ability to undergo reversible changes between different molecular states and accordingly molecular properties by excitation with light or other external stimuli. In this review, recent experiments on photo- and thermally induced molecular switching processes at noble metal surfaces utilizing two-photon photoemission and surface vibrational spectroscopies are reported. The investigated molecular switches can either undergo a trans-cis?isomerization or a ring opening-closure reaction. Two approaches concerning the connection of the switches to the surface are applied: physisorbed switches, i.e.?molecules in direct contact with the substrate, and surface-decoupled switches incorporated in self-assembled monolayers. Elementary processes in molecular switches at surfaces, such as excitation mechanisms in photoisomerization and kinetic parameters for thermally driven reactions, which are essential for a microscopic understanding of molecular switching at surfaces, are presented. This in turn is needed for designing an appropriate adsorbate-substrate system with the desired switchable functionality controlled by external stimuli.     

Concepts for Optical Control of Diffuse Discharge Opening Switches

Optical control of diffuse discharges is discussed as opening mechanism for rep-rated switches. Diffuse discharges can be sustained or terminated by making use of optogalvanic effects, that means resonant interaction of laser radiation with diffuse plasma. Independent of control mechanisms, the performance of diffuse discharge opening switches is strongly affected by such fill gas properties as attachment and electron mobility.     

Torsional control by intense pulses

We generalize the concepts of alignment and 3D alignment by moderately intense laser pulses to control both the overall rotations and the torsional motions of polyatomic molecules. Torsional control is applied to manipulate charge transfer events, hence introducing a potential route to light controlled molecular switches. Potential applications in areas such as molecular assembly, molecular spectroscopies, energy transfer, and molecule-based junctions are envisioned.     

Conductivity of carbon-based molecular junctions from ab-initio methods

Carbon nanomaterials (CNMs) are prompting candidates for next generational electronics. In this review we provide a mini overview of recent results on the conductivity of carbon-based molecular junctions obtained from ab-initio methods. CNMs used as nanoelectrodes and molecular materials in molecular junctions are discussed. The functionalities that include the nanomechanically controlled molecular conductance switches, negative differential resistance devices, and electronic rectifiers realized by using CNMs have been demonstrated.     

Mach–Zehnder interferometers in photonic crystals

Photonic crystal technology allows the creation of optical waveguides with low sharp-bending losses as well as ultra-low group velocity. This last property is particularly interesting to develop highly-compact optical devices based on the controlled modification of the optical phase of the signals traveling through the waveguides. Among these devices, the Mach–Zehnder interferometer acquires fundamental importance because it can be used as a building block of more complex optical devices and functionalities such as optical filters, wavelength demultiplexers, channels interleavers, intensity modulators, switches and optical gates. In this paper, the performance of a Mach–Zehnder interferometer consisting of two coupled-cavity waveguides with different lengths created in a two-dimensional photonic crystal is theoretically analyzed. We also provide simulation results using a finite-difference time-domain code that confirm the theoretical analysis. The main limitations in the performance of the structure are addressed and discussed.     

Memristive operations demonstrated by gap-type atomic switches

We demonstrate memristive operations using gap-type Ag₂S atomic switches, in which the growth and shrinkage of an Ag protrusion are controlled by using solid-electrochemical reactions. In addition to conventional memristive operations such as those proposed and demonstrated by resistive random-access memories (ReRAMs) using metal oxide compounds, gap-type Ag₂S atomic switches also show new types of memristive operations by storing information from input signals without changing their output until a sufficient number of signals are inputted. The new types of memristive operations resemble the learning process seen in neuroplasticity, where changes occur in the organization of the human brain as a result of experience.     

微机电光开关

对微机械光开关的特点和应用作了简要的论述 ,并对近年国外几种典型微机械光开关的结构、原理和研制方法作了简要的介绍和评述。这类新型的开关器件的主要优点是串话小 ,插入损耗小 ,消光比高 ,对波长和偏振不敏感 ,且体积小 ,造价低等 ,在光纤通信和光纤测试系统中具有广阔的应用前景     

Finite element analysis of optically controlled non-linear directional coupler switches

Optically controlled two-way optical switches are useful for high-speed photonic switches and rapidly reconfigurable optical interconnection networks. A directional coupler forms such a switch because the field can be switched from one waveguide to the other by altering the optical length of the waveguide. Nonlinear materials are incorporated in the waveguide so that the optical path length may be altered by using an optical control beam to vary the intensity of light. A finite element method is described that enables the modelling of the non-linear dual waveguide structure for arbitrary waveguide shapes. Spurious modes are avoided in the transverse magnetic field method and non-linearity is handled by iteration and assuming an equivalent non-linear relative permittivity.     

Fano resonance and spectral compression in a ring resonator drop filter with feedback

We propose a ring resonator drop filter with feedback loop which can form the other ring cavity to produce an asymmetric Fano-resonance line shape and mode compression. By properly adjusting the feedback loop, the asymmetric line shapes of the transmission spectra can be controlled and selectively mode compression of the circuiting intensity in the feedback loop is achieved. Such characteristics are useful for applications in ring resonator-based photonic devices such as all-optical switches, sensors and intracavity frequency selection single-mode laser.     

Evolution and stability of spatial solitons in a photorefractive two-wave mixing system

The dynamical evolution and stability of bright dissipative holographic solitons in biased photorefractive materials in which the self-trapping beam obtains a gain from the pump beam via two-wave mixing has been investigated numerically. Results show that these solitons are stable relative to small perturbations. Adjusting some system parameters, such as the bias field and the angle between beams, can easily control the generation of such solitons. Potential applications in optical switches or repeaters are discussed.     

Phase sensitivity of directional couplers

Directional couplers of various design have been treated widely, both theoretically and experimentally. However, in most cases directional couplers are designed as 1 to 2 port circuits. If both input ports are used, the phase of the guided waves has to be taken into account. The influence of the phase term on the switching behaviour of Δβ-reversal couplers is discussed as an example. It is shown that the phase difference of two waves coupled to both coupler input ports will not affect crossover and straight-through states, but all states in between. Therefore electrical controlled 2 to 2 port switches will become very sensitive, if low crosstalk is required. This effect can be used to design an all optical working switch or optical logic.     

Controlling self-Kerr nonlinearity with an external magnetic field in a degenerate two-level inhomogeneously broadened medium

The magnitude and sign of self-Kerr nonlinear coefficient in a degenerate two-level inhomogeneously broadened medium are simply controlled by an external magnetic field. By changing the external magnetic field we can switch a negative peak of Kerr nonlinear coefficient into a positive peak and vice versa, and transform a zero value of Kerr nonlinear coefficient into a positive or negative peak in resonant region. Such a controllable Kerr nonlinear coefficient can be used to manipulate the working characteristics of photonic devices such as optical switches and bistable elements.     

Synchronization by irregular inactivation

Many natural and technological systems have on/off switches. For instance, mitosis can be halted by biochemical switches which act through the phosphorylation state of a complex called mitosis promoting factor. If switching between the on and off states is periodic, chaos is observed over a substantial portion of the on/off time parameter plane. However, we have discovered that the chaotic state is fragile with respect to random fluctuations in the on time. In the presence of such fluctuations, two uncoupled copies of the system (e.g., two cells) controlled by the same switch rapidly synchronize.     

高效率微带线光导开关非线性特性的实验研究

本文报道了高效率微带线光导开关非线性输出特性的实验研究,给出了输出波形,并与普通微带线电路光导开关的输出进行了比较,指出了这种微带线电路光导开关非线性输出的高效率特性、双极特性及利用非线性光导开关研制新型高效率、高压、高功率超短电脉冲产生器的可能性.     

脉冲功率电源辐射电磁场测量与分析

 对采用三电极气体间隙放电开关的脉冲功率电源和采用可控硅开关的脉冲功率电源进行了辐射电磁场测量与分析。所研究的脉冲功率电源的脉冲持续时间为ms量级,电流峰值为几十到几百kA。使用多组微分式磁场探头和高采样率、高存储深度的数字示波器进行了磁场测量;通过探头校对实验,对探头系数进行了校验。通过对微分测量结果的校正与积分运算,得到了磁场的时域波形。分析了低频段按照探头系数的计算方法和积分处理方法的关系,总结了时域波形重构的一些方法。得到了两种电源的电磁场特性：三电极气体间隙放电开关产生的磁场频谱范围可达10 MHz,而可控硅开关产生的磁场在1 MHz以内;其辐射电场微弱。     

Quantum dynamics of tight-binding networks coherently controlled by external fields

With some reviews on the investigations on the schemes for quantum state transfer based on spin systems, we discuss the quantum dynamics of magnetically-controlled networks for Bloch electrons. The networks are constructed by connecting several tight-binding chains with uniform nearest-neighbor hopping integrals. The external magnetic field and the connecting hopping integrals can be used to control the intrinsic properties of the networks. For several typical networks, rigorous results are shown for some specific values of external magnetic field and the connecting hopping integrals: a complicated network can be reduced into a virtual network, which is a direct sum of some independent chains with uniform nearest-neighbor hopping integrals. These reductions are due to the fermionic statistics and the Aharonov-Bohm effects. In application, we study the quantum dynamics of wave packet motion of Bloch electrons in such networks. For various geometrical configurations, these networks can function as some optical devices, such as beam splitters, switches and interferometers. When the Bloch electrons as Gaussian wave packets input these devices, various quantum coherence phenomena can be observed, e.g., the perfect quantum state transfer without reflection in a Y-shaped beam, the multi-mode entanglers of electron wave by star-shaped network, magnetically controlled switches, and Bloch electron interferometer with the lattice Aharonov-Bohm effects. With these quantum coherent features, the networks are expected to be used as quantum information processors for the fermion system based on the possible engineered solid state systems, such as the array of quantum dots that can be implemented experimentally.      

Nanoelectronic Devices Based on Carbon Nanotubes

We review the state-of-the-art in the carbon nanotube (CNT) electronics. The emphasis is made on actually created devices. The history of discovery of fullerenes is outlined and their properties are considered. Experimental discovery of nanotubes and nanotube synthesis technologies are reviewed. The CNT conductivity dependence on the geometrical structure of nanotubes is discussed. Various nanoelectronic CNT devices, such as nanowires, heterojunctions, diodes, and field-effect transistors are presented. Quantum properties of CNTs at low temperatures are discussed. CNT-based mechanical devices, memory elements, and switches are considered. Field emission properties of CNTs are analyzed. The data on the developed CNT-based light-emitting elements and the manufactured pre-production models of CNT flat-panel displays are given.     

High-contrast interferometry based on anti-Stokes stimulated Raman scattering with broadband and narrow-band quasi-continuous-wave laser light

Two versions of an anti-Stokes stimulated Raman scattering (SRS) experiment are presented, one with narrow-band light, the other with broadband light. The interferograms exhibit, at optical periods, alternation between complete signal extinction and high signal intensity with much higher contrast than seen in ordinary linear interferometry. Furthermore, for broadband excitation, the envelope of the high-contrast SRS interferogram is limited to an ultrashort time period. Possible applications of such signals for use as switches or logic gates are discussed.     

Method of state code matrixes in the realization of optical switching using Perfect Shuffle

Based on the Left Perfect Shuffle (LPS) optical communication network constructed by cascade multi-stage LPS interconnection, using Looping algorithm, any arbitrary sequence of the input signals can be realized. However, instead of obtaining the simultaneous state codes of the same level node switches through mathematical analytical expressions directly, only routing tags of each channel can be obtained through mathematical analytical expressions so as to draw out topological chart of the network to obtain the state codes implied in the chart. Thus, the states of the switches cannot be directly programmed and controlled by computer in practical application. In this paper, based on the Looping algorithm, a method of stage code matrixes is presented to resolve this problem. By using the method, the simultaneous state codes of the same level’s four node switches can be directly obtained, which is convenient for the computer to provide controlled signals needed to finish the permutation for each node switch. The method of stage code matrixes provides further theoretical basis for the realization of optical switching by integration of Perfect Shuffle and high-speed optical switches.