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.     

All-Optical Switching Based on Azo Polymer Material

Conventional all-optical switches based on azo polymer films and the all-optical switches based on the attenuated total reflection （ATR） geometry are investigated. A conventional switch system, including a pump beam of 532 nm and a probe beam of 650 nm, is based on the photoinduced birefringence effect of azo polymer. An ATR switch in a prism-multilayer configuration is achieved by changing the reflectance of the probe beam with an external pump beam. The ATR method provides the substantial improvement of the speed and the efficiency of the modulation over the conventional method. Although the azo polymer response still remains relatively slow, an enhanced nonlinear refractive index of the azo polymer film can effectively increase the modulation.     

Omnidirectional and controllable switching behavior in a multiple photonic quantum well system with single-negative material heterostructure

We propose and demonstrate theoretically omnidirectional and controllable switching behavior by combining the advantages of the controllable properties of a photonic quantum well system and the omnidirectional resonant defect modes of single-negative material heterostructures. Our numerical results reveal that the frequency positions of strong localized states are different for odd numbers and even numbers of wells, which can be used to design an all-optical switch by adding or reducing one well. Furthermore, the frequency position can be adjusted by modifying the width of the wells. Compared to conventional all-optical switches, the frequency position of the proposed switch is not only adjustable, but it is also insensitive to the incidence angle of light. The proposed method thus provides a simple way of designing an omnidirectional and controllable all-optical switch.     

纳米光子学全光开关研究进展

全光开关是全光网络和数字光信息处理的基本器件,该器件主要基于非线性光学原理．自激光发明以来,对该器件的研究已历时半个世纪．虽然全光开关的基础研究十分活跃,研究成果丰硕,但是至今尚未做出实用器件．文章分析了全光开关面临的困难,指出只有在极小的时空条件下,也就是采用飞秒激光驱动的纳米尺寸器件,才有可能研制出低开关功率、高开关速度、低插入损耗的实用的全光开关器件．文章简要介绍了近10年来纳米全光开关的研究成果,包括纳米尺寸干涉仪开关（空间开关）、量子限制光双稳触发器（时间开关）、半导体光放大器的波长转换器（波长开关）、光子晶体带隙移动开关和表面等离子体激元开关（强度开关）等5类16种典型的纳米全光开关器件．     

Ultrafast all-optical signal processing with Symmetric Mach–Zehnder type all-optical switches

We present Symmetric Mach–Zehnder (SMZ) type all-optical switches: an SMZ all-optical switch, a polarization-discriminating SMZ (PD-SMZ) all-optical switch, and a delayed interference signal wavelength converter (DISC). These switches are capable of ultrafast, low control power, and low chirp switching, which is not restricted by slow relaxation of highly efficient nonlinearities. High repetition operation unrestricted by slow relaxation is also possible for these switches. This is because of a push–pull modulation scheme or sometimes called a differential phase modulation scheme. These three devices are similar, but different in some important aspects, thus a comparison is made among the three. Then semiconductor optical amplifiers (SOAs) are discussed as a nonlinear phase shifter for these devices. Then, ultrafast all-optical signal processing using SOA based SMZs is demonstrated. Error-free demultiplexing from 168 to 10.5 Gbit/s is presented, in which a hybrid-integrated SMZ (HI-SMZ) is used as a demultiplexer. In pulse regeneration experiment, the signal pulses at 84 Gbit/s are regenerated by the PD-SMZ and the regenerated pulses are demultiplexed to 10.5 Gbit/s by the HI-SMZ to verify error-free operation. The retiming capability of this scheme is quantitatively demonstrated. Also presented is error-free all-optical wavelength conversion at 168 Gbit/s using the DISC. These results represent the fastest error-free operations reported to date in each category.     

光梯度力驱动的纳米硅基光开关

通过一道光改变另一道光的传输路线是光子集成网络中重要而长远的目标, 然而, 由于硅材料的光学非线性较弱, 在硅材料上实现开关的全光控制难以实现. 因此本文提出了一种由光梯度力驱动的纳米硅基光开关, 实现了硅基光开关的全光控制. 该光开关由一个部分悬空的微环谐振器和一个交叉波导结构构成, 当通入一道控制光时, 悬空的微环谐振器在光梯度力的作用下发生弯曲, 微环谐振器的谐振波长随之发生变化, 从而实现光信号的传输路线发生改变. 该光开关利用纳米光子制造技术在标准绝缘体上硅晶圆上制造, 实验数据得出其最小消光比为10.67 dB, 最大串扰为 -11.01 dB, 开关时间分别为180 ns和170 ns. 该光开关具有尺寸小, 响应速度快, 低损耗和可拓展等优点, 在片上集成光路、高速信号处理以及下一代光纤通信网络中具有潜在应用.     

SOA-assisted Sagnac switch and investigation of its roadmap from 10 to 40 GHz

Future broadband optical communications networks will rely on all-optical switches to perform a set of processing functions exclusively in the optical domain. Interferometric optical switches using semiconductor optical amplifier (SOA) nonlinearities can perform efficient optical switching with few tens of fJ control energies and short fiber lengths allowing for monolithic integration. In this paper we present work performed with a three terminal SOA-assisted Sagnac interferometer. We review all-optical Boolean AND and XOR logic results at 10 GHz and 10 Gb/s for full duty cycle and pseudo-random data pattern operation, respectively, achieved with adequate contrast ratios, remarkably low switching energies and low pattern dependence. The ability of the device to be cascaded was proved up to 10 GHz by recirculating stably for hours arbitrary pattern profiles. Finally, and in view of the extension of photonic networks single channel data rates beyond 40 Gb/s, the performance of the switch was simulated in terms of its critical parameters. The obtained results showed that full switching operation at 40 GHz or higher is feasible either by deploying gain recovery reduction techniques in bulk and quantum well SOAs or alternatively other technologically advanced optical devices, such as quantum dot SOAs.     

一种新型全光开关

提出了一种用指数型变耦合系数定向耦合器同高斯型变耦合系数定向耦合器级联所构成的新型全光开关。理论分析及数值模拟均表明,它同用常系数定向耦合器级联所得的器件相比,具有一个很大的优点,即可以消除开关曲线在过开关区中的振荡,因而具有更好的开关特性;同时,它同用高斯型变耦合系数定向耦合器级联所得的器件相比,具有陡峭的动态开关区(即功率透过率从0逐渐升至1的区域)。综上所述,该级联耦合器更加适合于做全光开关,且在满足一定的开关曲线的要求下,可以通过改变各级联耦合器的参量以改变单元耦合器的数目。     

Optically bistable nonlinear interference filters for use with near-infrared laser diodes

ZnSe nonlinear interference filters, configured as optothermal bistable etalons with absorbed transmission (BEAT) devices, have been operated as all-optical switches using 830 nm diode laser illumination and fibre-optic coupling. Stable switching at powers down to 3 mW have been demonstrated for spot diameters of 10 μm. An observed increase in switch power when using large numerical-aperture illumination is analysed in terms of a reduction in effective cavity finesse.     

Au/MXene based ultrafast all-optical switching

All-optical switches have arisen great attention due to their ultrafast speed as compared with electric switches. However, the excellent optical properties and strong interaction of two-dimensional (2D) material MXene show great potentials in next-generation all-optical switching. As a solution, we propose all-optical switching used Au/MXene with switching full width at half maximum (FWHM) operating at 290 fs. Compared with pure MXene, the Au/MXene behaves outstanding performances due to local surface plasmon resonance (LSPR), including broadband differential transmission, strong near-infrared on/off ratio enhancement. Remarkably, this study enhances understanding of Au/MXene based ultrafast all-optical switching red-shifted about 34 nm in comparison to MXene, validating all optical properties of Au/MXene opening the way to the implementation of optical interconnection and optical switching.     

Interferometric ultrafast SOA-based optical switches: From devices to applications

All-optical switches are fundamental building blocks for future, high-speed optical networks that utilize optical time division multiplexing (OTDM) techniques to achieve single channel data rates exceeding 100 Gb/s. Interferometric optical switches using semiconductor optical amplifier (SOA) non-linearities perform efficient optical switching with < 500 fJ of control energy and are approaching optical sampling bandwidths of nearly 1 THz. In this paper, we review work underway at Princeton University to characterize and demonstrate these optical switches as processing elements in practical networks and systems. Three interferometric optical switch geometries are presented and characterized. We discuss limitations on the minimum temporal width of the switching window and prospects for integrating the devices. Using these optical switches as demultiplexers, we demonstrate two 100-Gb/s testbeds for photonic packet switching. In addition to the optical networking applications, we have explored simultaneous wavelength conversion and pulse width management. We have also designed high bandwidth sampling systems using SOA-based optical switches as analog optical sampling gates capable of analyzing optical waveforms with bandwidths exceeding 100 GHz. We believe these devices represent a versatile approach to all-optical processing as a variety of applications can be performed without significantly changing the device architecture.     

All-optical switch and limiter based on nonlinear polarization in Mach-Zehnder interferometer coupled with a polarization-maintaining fiber-ring resonator

A novel all-optical switch based on nonlinear polarization mechanism using polarization-maintaining fiber ring with a polarization rotator is proposed. Optical switching with low threshold of mW order and optical limiting with broader limiting range, less fluctuation, higher damage threshold and response speed are demonstrated numerically. The deterioration of switching and the improvement of limiting originating from losses are also studied. Considering the tradeoff between switching power and bandwidth, the way to increase bandwidth is discussed.     

Micromagnetic investigation of all-optical switching

This Letter investigates all-optical magnetization switching from micromagnetic perspective. The influence of circularly polarized light on a magnetic sample was considered to be both directly through the inverse Faraday effect and indirectly aided by thermal induced effects by the laser beam. Dependence of all-optical switching on pulse duration, laser intensity and the magneto-optical susceptibility strength is studied. An important aspect of this investigation is the analysis of how the cooling process influences the successive switches, especially through limiting the successive writing time.     

基于自相位调制和交叉相位调制的全光开关特性研究

提出一种优化含有掺铒光纤放大器的非线性Sagnac干涉仪全光开关的新方法,建立了基于自相位调制和交叉相位调制两种解析模型,讨论了掺铒光纤放大器的小信号增益和饱和输出功率对开关性能的影响.分析表明掺铒光纤放大器的性能参量对开关所需要的Sagnac环中光子晶体光纤长度产生限制.当采用相同长度的光子晶体光纤时,基于交叉相位调制方式的全光开关与基于自相位调制方式的全光开关相比能够显著降低开关功率.采用分布傅里叶法数值求解非线性薛定谔方程,优化了开关结构,讨论了重复频率为40 GHz脉宽为5 ps的高斯型信号脉冲在开关时沿Sagnac环的传输特性.模拟结果表明,通过合理选择高非线性光子晶体光纤长度和掺铒光纤放大器的性能参量能够实现超低开关功率（＜1 mW）的开关操作.     

掺杂浓度与溶剂对偶氮聚合物薄膜全光开关

用重复旋转涂膜法制备了乙基红(ER)偶氮染料与聚甲基丙烯酸甲酯(PMMA)掺杂聚合物薄膜和乙基橙(EO)与聚乙烯醇(PVA)掺杂聚合物薄膜.测量了两种聚合物薄膜样品全光开关特性,比较分析了薄膜样品的掺杂浓度和溶剂对全光开关效应的影响,实验结果表明:增加掺杂浓度和溶剂,极性薄膜样品的全光开关效应增强且开关的本底信号增大,但对开关的响应速度影响很小;选择合适的掺杂浓度和强极性溶剂,在室温和几个mW的弱功率控制光条件下聚合物薄膜具有毫秒级开关响应时间和40%以上的开关调制深度,最大的调制深度达72%以上.     

Study on all-optical switching characteristics of ethyl orange-doped polymer film

The all-optical switching polymer thin films with azobenzene dye ethyl orange as the guest material and polyvinyl alcohol (PVA) as the host material were prepared by adulteration and spin-coating methods. The all-optical switching characteristics of the samples were measured at different intensities and modulation frequencies of the pump beam (532 nm, CW); the influence of doping concentration on the all-optical switching effect of the films was studied. It is shown that, under room temperature conditions and with a low pump power of 6 mW, the all-optical switch has a response time of about 2 ms and a modulation depth of 45%, and the maximal modulation depth reaches 90%. In addition, it is found that samples with higher doping concentration show a stronger all-optical switching effect but a larger background signal, and good switching performance is obtained by choosing the doping concentrations from 0.8% to 2% of the sample.     

Photonic switching in GaAlAs optical strip waveguides by photo-induced electroabsorption

GaAlAs strip waveguides embedded in unbiased pn-junctions are employed for all-optical switching. The underlying physical mechanism is a combination of the photovoltaic effect and the conventional Franz-Keldysh effect, thus it is called the photo-induced Franz-Keldysh effect or photo-induced electroabsorption. Experimental as well as theoretical results are given and show good agreement. In the experiments the transmitted light power of a probe beam is switched by 3 dB due to an injected control beam at input light power levels of about 0.5 mW each. The dynamics of this all-optical switch is limited by RC time constants.     

Laser Trimming for Adjustment of Grating Offset in Phase-Shifted Fiber Grating Coupler for All-Optical Switching Application

We theoretically investigated laser trimming to adjust grating offset in phase-shifted fiber grating coupler (FGC) for all-optical switching application. It was clarified that the trimming made the extinction ratio higher in all-optical FGC switch.     

All-optical switching effect based on azodye-doped polymer thin films

A simple all-optical switch based on photoinduced birefringence effect is demonstrated in azo dye (DR1) doped polymer (PMMA) thin films. The all-optical switching effect has been studied at different control beam power and different temperatures of the sample. With a control power of 30.7 mW and at 56 ℃, the response time of the switching is less than 5 ms, and the depth of the modulation reaches 80%.     

All-optical reconfigurable logic operations with the help of terahertz optical asymmetric demultiplexer

An all-optical reconfigurable logic operation essentially constitutes a key technology for avoiding complex and speed limited optoelectronics conversions and performing various processing tasks. All-optical reconfigurable logic operations with the help of terahertz optical asymmetric demultiplexer (TOAD) is proposed and described. The paper describes the all-optical reconfigurable logic operations using a set of all-optical multiplexer and optical switches. We have tried to exploit the advantages of TOAD-based switch to design an integrated all-optical circuit which can perform the different logic operations AND, XOR, NOR and NOT. Numerical simulation confirming described methods is given in this paper.