Simulation and optimization of a polymer directional coupler electro-optic switch with push-pull electrodes

Structural model and design technique are proposed for a polymer directional coupler electro-optic switch with rib waveguides and push-pull electrodes, of which the electric field distribution is analyzed by the conformal transforming method and image method. In order to get the minimum mode loss and the minimum switching voltage, the parameters of the waveguide and electrode are optimized, such as the core with, core thickness, buffer layer between the core and the electrode, coupling gap between the waveguides, electrode thickness, electrode width and electrode gap. Switching Characteristics are analyzed, which include the output power, insertion loss, and crosstalk. To realize normal switching function, the fabrication error, spectrum shift, and coupling loss between a single mode fiber (SMF) and the waveguide are discussed. Simulation results show that the coupling length is 3082 μm, push-pull switching voltage is 2.14 V, insertion loss is less than 1.17 dB, and crosstalk is less than −30 dB for the designed device.     

Optimal design and analysis of a high-speed, low-voltage polymer Mach-Zehnder interferometer electro-optic switch

Detailed model, analysis and design technique are presented for simulating a high-speed polymer Mach-Zehnder interferometer (MZI) electro-optic switch with push-pull dual driving electrodes and rib waveguides. The novel formulas of the time-domain response are derived. Thorough optimization and simulation for the designed device are performed. The total length of the basic function unit of the switch is about 5049 μm, the push-pull switching voltage is 2.23 V, the switching time is 18.1 ps, and the insertion loss and crosstalk are less than 2.64 and −30 dB, respectively, within the range of the operation wavelength from 1534 to 1566 nm. These results are in good agreement with those obtained from the beam propagation method (BPM).     

Theory of 2×2 switch based on electro-optic and piezoelectric effects in photorefractive LiNbO3 crystal

Based on the electro-optic and piezoelectric effects, the principle of a 2×2 bypass-exchange switch in photorefractive LiNbO₃ crystal is discussed. In photorefractive volume grating, the Bragg condition can be changed by applying a field during readout. That is, by applying a specific field E_s or zero, the diffraction efficiency will be 0 or 1, respectively and this property can be used to realize the bypass or exchange operation of the switch. In this paper, considering both the piezoelectric and electro-optic effects caused by the applied electric field, we analyzed relations of both the specific field and the incident intensity ratio with respect to the writing angles and polarizations of writing beams.     

Analysis of polymer electro-optic microring resonator switches

The structure and the principle for the polymer electro-optic microring resonator (MRR) switch are proposed as well as the transfer functions. The structural parameters are optimized; the transmission characteristics are analyzed including the output power, switching time, switching voltage, insertion loss, and crosstalk. When the operation voltage is 0 V, the insertion loss and crosstalk are ∼1.2 and −20.2 dB, respectively; when the operation voltage is 10.0 V, those are ∼0.35 and −20.0 dB, respectively. Furthermore, a novel method is presented for analyzing time-domain response of the device and the switching time is determined to be ∼10.71 ps. These results indicate the favorable switching functions of the designed device.     

Skin-effect analysis of a shielded polymer Y-fed coupler electro-optic modulator over a wide bandwidth of 94 GHz

A novel technique and related formulations are proposed for analyzing the influences of the skin-effect on the performances of a polymer Y-fed coupler electro-optic modulator with shielded push-pull micro-strip electrodes. Using the extended point-matching method, coupled mode theory and electro-optic modulation theory, thorough design and optimization are performed. By introducing the effective applied voltage, formulas of the high-frequency response under skin-effect are deduced, and characteristics under skin-effect are analyzed. Under the central wavelength of 1550 nm, the half-wave voltage is as low as 1.097 V for the device with an active region length about 8.884 mm. Considering the influences of the skin-effect, the 3-dB modulating bandwidth of the microwave signal is up to 94 GHz. A high extinction ratio of more than 20 dB and a low insertion loss of less than 4.18 dB are achieved when the microwave frequency is below 68 GHz under skin-effect. This design technique is proven to be accurate by the comparison with the beam propagation method (BPM).     

Design of wide-spectrum polymer Mach-Zehnder interferometer electro-optic switches using two symmetric N-th order phase-generating couplers

To enlarge the output spectrum, a novel reasonable structure of one kind of Mach-Zehnder interferometer (MZI) electro-optic (EO) switches containing two symmetric N-th order phase generating couplers (PGCs) is presented, and thorough model, analysis and design technique are proposed. A non-linear least square method is investigated for optimizing the PGC structure to eliminate the phase difference error caused by the wavelength variation. Under the central wavelength of 1550 nm, optimization and simulation are performed on three MZI EO switches using two first, second and third order PGCs, respectively. The switches exhibit a low switching voltage of 1.156 V with an active region length of 4 mm. The output spectrums covering the whole S-C-L bands are as wide as 320, 390 and more than 435 nm, respectively, the insertion loss are less than 5.57, 5.98 and 7.90 dB, respectively, and the crosstalk is less than −30 dB over the wide wavelength ranges, for the three designed switches. The design technique is supported to be feasible by the comparison with beam propagation method (BPM).     

单脉冲电光开关击穿时间延迟及抖动的减小方法

减小单脉冲等离子体电极普克尔盒电光开关击穿时间延迟与抖动问题是提高大口径电光开关性能的关键。利用紫外线照射在阴极上的外光电效应,使阴极产生次级电子发射,形成稳定的初始电子流,在高压脉冲作用下普克尔盒内的初始电子产生快速繁流放电,使盒内氦气击穿。实验证明该方法可以减小开关的击穿时间延迟及抖动,使击穿时间延迟平均下降了36%,平均抖动时间下降88%。     

Design of a polymer directional coupler electro-optic switch using two-section reversed electrodes

By using the coupled mode theory, electro-optic modulation theory, conformal transforming method and image method, the structure is designed, the parameters are optimized, and the characteristics are analyzed for a polymer directional coupler electro-optic switch with two-section reversed electrodes. Simulation shows that the designed device exhibits excellent switching functions. Under the operation wavelength of 1550 nm, the electro-optic coupling region length is 4751 μm, the cross-state and bar-state voltages are about 1.22 and 2.65 V, and the insertion loss and crosstalk are less than 2.21 and −30 dB, respectively. By slightly adjusting the state voltages, the blight of the fabrication errors on the switching characteristics can be easily eliminated. The calculation results of the presented technique are in good agreement with those of the beam propagation method (BPM).     

Enhanced electro-optic response of a poled polymer in a reflective microcavity

We investigated the electro-optic (EO) response of a reflective planar microcavity with a poled polymer spacer using reflection ellipsometry. We designed and fabricated the microcavity to have an enhanced local field in the EO polymer spacer and evaluated the resulting enhancement in the voltage-induced phase difference between the s- and p-polarized components. The phase difference obtained was 56 times larger than that for the EO polymer alone. This enhancement is attributed to the polarization-dependent local field effect for oblique incidence.     

一种多组电极的高功率多脉冲气体开关

 设计了一个有3组电极的开关，给出了开关的结构，分析了多组电极共存的可行性和开关内的电场，利用通用电路模拟软件对通过开关的电流进行了计算。此开关在单组电极导通时，耐电压约为50kV，电流100kA以上，电流脉宽约20μs；在间隔1ms，脉宽为μs级的预触发脉冲触发下，开关能在电感负载中产生间隔为1ms的3个电脉冲，实验测得平均峰值电压约38kV，电流约100kA，脉宽约20μs。     

圆柱电极激光触发开关击穿前的模拟计算

在加入SF6气体与电子的碰撞反应截面后,利用基于PIC-MCC方法的XOOPIC程序,对天光Ⅰ号激光装置预放大器上的圆柱电极激光触发开关进行击穿前流柱形成过程的模拟计算。详述了模拟条件的选择及激光触发条件的等效,并给出了模拟结果。模拟结果表明,在弧道初始半径约为250 μm的条件下,经过0.15 ns后正离子到达阴极,开关导通。因此验证了通过PIC-MCC方法模拟,可以为开关弧道的电阻的动态变化的电路模拟给出初始条件,使之能够更为准确的预测开关的导通行为,为开关设计提供了一个新的工具。     

Design and optimization of novel ultra-compact SOI multimode interference optical switch

In this paper, an ultra-compact 3 × 3 SOI multimode interference optical switch is presented. There is only one hyperbolic multimode waveguide in the switch. By changing the refractive index of one or two parts within the hyperbolic multimode waveguide, the switch can realize on and off functions between any pair of input and output ports. The various states of the switch were simulated and analyzed using the finite difference beam propagation method (FD-BPM), the structure parameters of the switch were also designed and optimized. The optimized switch has excellent properties and the whole size of the switch is less than 4 mm.     

圆柱电极激光触发开关击穿前的模拟计算

在加入SF6气体与电子的碰撞反应截面后,利用基于PIC-MCC方法的XOOPIC程序,对天光Ⅰ号激光装置预放大器上的圆柱电极激光触发开关进行击穿前流柱形成过程的模拟计算。详述了模拟条件的选择及激光触发条件的等效,并给出了模拟结果。模拟结果表明,在弧道初始半径约为250μm的条件下,经过0.15 ns后正离子到达阴极,开关导通。因此验证了通过PIC-MCC方法模拟,可以为开关弧道的电阻的动态变化的电路模拟给出初始条件,使之能够更为准确的预测开关的导通行为,为开关设计提供了一个新的工具。     

1×|N 信道聚合物微环谐振器电光开关阵列的开关特性

利用耦合模理论、电光调制理论和微环谐振理论,提出了一个完善合理的聚合物微环谐振器电光开关阵列模型.该器件由1条水平信道、N条竖直信道和N个微环构成,在微环上施加不同方式的驱动电压,可以实现N＋1条信道的开关功能.以1×8信道结构为例,在1 550 nm谐振波长下对该器件进行了优化设计和模拟分析.其结果是：微环波导芯的截面尺寸为1.7×1.7 μm2,波导芯与电极间的缓冲层厚度为2.5 μm,电极厚度为0.2 μm,微环半径为13.76 μm,微环与信道间的耦合间距为0.14 μm,输出光谱的3 dB带宽约为0.05 nm,开关电压约为12.6 V,插入损耗约为0.67~1.26 dB,串扰小于－20 dB,开关时间约为11.35 ps.     

等离子体电极普克尔盒电光开关单脉冲过程数值模拟

采用流体模型对等离子体电极普克尔盒(PEPC)电光开关单脉冲过程进行了数值模拟分析.模型包括带电粒子连续性方程、动量守恒方程、电子平均能量方程及空间电位泊松方程.分别采用隐式指数差分格式，超松弛迭代法(SOR)和经典四阶龙格-库塔法(R-K)对带电粒子连续性方程，泊松方程和电子平均能量方程进行数值求解.模拟分析了PEPC单脉冲过程中的带电粒子浓度、电子温度、空间电场、PEPC的放电电流、晶体两侧电压和开关效率的时间演化特性.模型得出了PEPC中气体放电等离子体的微观物理过程与PEPC宏观参量的关系，对设计 关键词： 等离子体电极普克尔盒 电光开关 数值模拟 气体放电     

Measurements of phase retardation and principal axis angle using an electro-optic modulated Mach–Zehnder interferometer

This paper presents an electro-optic modulated circular heterodyne modified Mach–Zehnder interferometer and a convenient two-phase signal-processing algorithm for the measurement of variations in the magnitude of phase retardation and the angle of principal axis in optical materials. The developed method solves the problems of normalized intensity jump and limited phase retardation measurement range associated with the circular heterodyne interferometer proposed previously. The present method uses a saw-tooth wave signal to drive an electro-optic (EO) modulator, and employs a lock-in amplifier to demodulate the principal axis angle and the phase retardation. Specifically, this paper considers two main sources of measurement errors, namely the misorientation of the EO modulator and the reflection phase retardation of the beam splitter. Furthermore, the study develops calibration procedures and identifies a means to minimize measurement errors induced by the reflection phase retardation of the beam splitter.     

Fourier analysis of a polymer directional coupler electro-optic switch with two-section cosine-transitive CPWG electrodes: A new theoretical view

By using two-section cosine-transitive coplanar waveguide grounded (CPWG) electrodes, a polymer directional coupler (DC) electro-optic (EO) switch is optimally designed with both relaxed fabrication tolerance under cross-state and high switching speed over 100 GHz. As a new theoretical view, based on Fourier transformation, a Fourier analysis technique and related formulas are presented with respect to the time- and frequency-domain responses under high-speed modulating and switching operations. Under 1550 nm, the bar- and cross-state voltages are 0 and 2.669 V, respectively, for the switch with a total length of 8378 μm. The insertion loss and crosstalk are less than 3.887 and ? 30 dB, respectively. The 3-dB modulating bandwidth and cutoff switching frequency are about 110 and 131.6 GHz, respectively, and the 10–90% rise time and fall time are both about 3.80 ps. Owning to this configuration, its cutoff switching frequency is enhanced to 9 times of that of our previously reported EO switch with two-section separated reversed electrodes, which expands the ultra-high speed and large capacity applications for such switches. The proposed Fourier analysis method can also be adopted to evaluate the responses under the operation of any other form driving signals with Fourier transformation.     

A 1 × 2 optical switch using one multimode interference region

A 1 × 2 optical switch using only one multimode interference (MMI) region is designed and demonstrated in GaAs/AlGaAs. This design makes a single MMI region works as MMI coupler using paired interference at “off” state and symmetric interference at “on” state. By injecting a current of 110 mA, the measured on/off ratio and crosstalk are 23 dB and 33 dB, respectively in the demonstrated device with GaAs/GaAlAs.     

Measurement of the electro-optic coefficient of polymer thin films with better spatial resolution

A method for measuring the electro-optic coefficient of polymer films on the basis of an asymmetry Fabry–Perot cavity is introduced. The sample layer is located between two aluminium layers, which are deposited on glass substrates by thermal evaporation. This layer structure is objected to a laser beam, and a variable voltage is applied to the aluminium films resulting in a modulation of the transmitted laser power. The electro-optic coefficient γ₁₃ of the poled polymer film can be calculated by evaluating the Fabry–Perot equation. The spatial resolution is tested with a polymer film that was poled by a needle corona discharge in air through a metal grating with a period of 120 μm. By scanning the sample plate in the direction perpendicular to the grating lines, the spatial resolution is also demonstrated according to the spacing of the poled structure.     

Investigation of the linear electro-optic effect for the guest–host polymer DR13/PEK-c thin films

The polyetherketone (PEK-c) guest–host polymer thin films doped with disperse red 13 were prepared by spin-coating method. The corona poling condition was optimized by the poling profiles. The polymer films were poled by corona-onset poling at elevated temperature, and the corona poling setup includes a grid voltage making the surface-charge distribution uniform. The linear electro-optic coefficients of the poled polymer films have been determined at λ=632.8 nm by using a new simple interferometric technique, which is based on compensating the change of the optical length due to the electro-optic effect of the poled polymer film by the anti-piezoelectric effect of a quartz crystal.