一种反射率、带宽、波长可调的微环反射腔镜

基于SOI的光学微环谐振腔具备低功耗、高集成 、高灵敏等特点而被广泛应用于光互连、光通信和光信息传输 等很多方面,本文利用耦合模理论,微环谐振理论和热光调制理论,提出了一种可以同时达 到反射率可调、带宽可调和 波长可调的微环反射腔镜,波长选择在1550 nm 附近 ,微环半径设置为10 μm,硅波导尺寸选择220 nm的条波导,波导 宽度为450 nm。利用转移矩阵方法和matlab仿真软件计算并仿真讨论 了输出光谱与耦合系数k等参数的变化关系。仿真 结果证明,该器件反射率变化为15%(在 无损耗的情况下),带宽调谐范围为0.25 nm～0.95 nm,通过在微环上加热 电极可以实现一个FSR(自由光谱范围)范围波长的调谐。该器件在高速光网络传输、光增 益谱均衡和信道选择方面有着重要应用。     

支撑光网络发展的Si基光子集成器件的研究进展

本文报道了可用于光网络系统终端OADM和OXC的Si基长波长量子阱窄带响应光电接收器、MOEMS和F-P TO宽频域光学滤波器、M-Z型 TO光开关和MMI多路分束器以及可变光强衰减器.用应变层SiGe/Si MQW研制的RCE光电接收器响应谱半宽FWHM<6nm,外量子效率η>4.2%;采用表面微机械加工的桥式光学滤波器,当外加电压0→50V,连续可调谐范围达90nm;彩全平面工艺研制的F-P腔TO滤波器,当外加电流0→57mA时,连续可调谐范围达23nm,FWHM<0.5nm.在SOI Si基片上研制的M-Z TO波导光开关,开关时间<30μs,功耗～100mW.开关消光比为-13dB和-10dB,1×4MMI多路分束器输出光声的不均衡性<0.36dB,总插入损耗为6.9dB.用背向对接的MMI构成的M-Z干涉仪实现了光强的可变调最大衰减量26dB,响应时间为100μs,插入损耗为4.8～7dB.     

支撑光网络发展的Si基光子集成器件的研究进展

本文报道了可用于光网络系统终端OADM和OXC的Si基长波长量子阱窄带响应光电接收器、MOEMS和F-P TO宽频域光学滤波器、M-Z型 TO光开关和MMI多路分束器以及可变光强衰减器.用应变层SiGe/Si MQW研制的RCE光电接收器响应谱半宽FWHM<6nm,外量子效率η>4.2%;采用表面微机械加工的桥式光学滤波器,当外加电压0→50V,连续可调谐范围达90nm;彩全平面工艺研制的F-P腔TO滤波器,当外加电流0→57mA时,连续可调谐范围达23nm,FWHM<0.5nm.在SOI Si基片上研制的M-Z TO波导光开关,开关时间<30μs,功耗～100mW.开关消光比为-13dB和-10dB,1×4MMI多路分束器输出光声的不均衡性<0.36dB,总插入损耗为6.9dB.用背向对接的MMI构成的M-Z干涉仪实现了光强的可变调最大衰减量26dB,响应时间为100μs,插入损耗为4.8～7dB.     

采用单环微谐振器的光滤波器特性及其局限性

对采用单环微谐振器的光滤波器的特性进行了分析。在给出的传递函数和相关特性公式基础上，分析了出／入环光耦合系数与通带带宽和通带消光比间的关系，指出了它们之间、以及与自由谱范围间存在的相互约束；分析并给出了单环光滤波器的通带带宽比例，带宽比例值不依赖于任何器件结构参数，是限制单环微谐振器作为实用光滤波器的主要因素；分析了存在于微环中光的损耗对单环光滤波器输出的影响，小的光损耗即会导致滤波响应的巨大衰减，大的光损耗则更是会导致带宽的展宽和带宽比例值的增大。     

共路外差干涉测量液晶空间光调制器相位特性

为了对液晶空间光调制器进行高精度的校准, 使其满足线性相位调制的应用需求, 采用共路外差干涉法测量了液晶空间光调制器的相位调制特性, 分析了实验系统的测量原理, 取得了液晶空间光调制器相位调制量随输入灰度值变化的实验数据, 并进行了线性校准。结果表明, 实验中所用的液晶空间光调制器的最大相位调制量为2.55π, 利用反插值法对20~240灰度范围内的相位调制曲线进行线性校正后的理论相位调制曲线非常接近理想线性曲线, 相位调制曲线与理想线性调制曲线的相关系数可达0.9996;该测量方法可克服传统测量方法对图像处理的依赖性, 具有较高的测量精度, 相位调制量直接通过锁相放大器就可获得。该研究为基于液晶空间光调制器的高精度波前校正和精密测量提供了参考。     

新型电光逻辑门的设计及计算机图形光谱

光逻辑门是未来全光网络中光信息处理的核心元件,它可以实现高速光包交换,全光地址识别,数据编码,奇偶校验,信号再生等功能。采用微环谐振器设计了一种新型的电光逻辑门,结构通过三个非对称微环组成,分析耦合区的传输矩阵方程得出加载电压信号的变化能够实现微环折射率的变化,利用光强的逻辑开关特性可以实现光门逻辑。计算机仿真验证了工作波长1 600 nm时,实现的高电平50.7 V定义为逻辑1,低电平0 V定义为逻辑0,通过光强变化得出了6位逻辑运算;整个系统的响应时间理论上得到了1.8 ps,运算速率可达近200 Gbit/s。逻辑的双稳态分析中得出:微环发生最大谐振值时对应的控制波长等于微环未发生形变前的谐振波长和偏移量之和;调制可以通过微环谐振波长实现控制。这一研究对于未来全光通信的实现具有一定的意义。     

1967～2033 nm波段硅基可调谐外腔半导体激光器设计与仿真

2μm波长附近可调谐半导体激光器在分子光谱学和光通信领域中有广阔的应用前景。基于绝缘体上硅（SOI）平台,对2μm波长附近可调谐半导体激光器的外腔部分进行了设计优化。分析了不同尺寸光波导的模式损耗特性、单个微环谐振腔受总线波导耦合间距的作用以及总线波导光反馈终端对外腔半导体激光器性能的影响。并提出了一种具有高工艺兼容度的多模环形光波导光反馈结构。所设计的可调谐半导体激光器硅基外腔可通过环形波导上的镍铬合金微加热器进行0.1 nm/K的高精度调谐,对单个微加热器施加3.2 V电压时,调谐范围可达66 nm(1967～2033 nm)。     

基于液晶光阀和光束分析仪的Goos-Hänchen位移的简单测量

提出一种基于液晶光阀（LCLV）和光束分析仪（LBP）直接测量Goos-Hänchen（GH）位移的新方法。在文中我们首先研究了LCLV对光偏振态调制的特性,结果发现,当控制电压发生变化时,光的偏振态也随之变化。然后利用LCLV对光偏振态的调制和LBP记录光斑的重心位置的变化,直接测量出TE和TM两种偏振态入射时棱镜单界面反射光束的GH位移差。这个探测方法简单,不需要复杂的外部处理电路,且实验结果与理论结果很吻合,这个方法也可以进一步直接测量二维位移。     

耦合系数对串联双微环谐振器滤波特性的影响

多个光波导微环谐振器的组合可扩展自由光谱范围和改善滤波特性。推导了串联双微环谐振器中两个微环与直波导的耦合系数不限定为相同时的理想耦合条件,针对无损耗情况时光从与小环耦合的直波导入射的情形,计算了理想耦合条件下主谐振峰带宽、形状因子以及伪模的峰值透射率随耦合系数变化的情况,显示了耦合系数对滤波特性影响的规律。计算分析表明,当两个微环与直波导的耦合系数不相等时,可以取得较为均衡的良好滤波特性,同时有更多的设计灵活性。     

带反馈双波导耦合微环共振器光学特性的理论研究

设计了一种带反馈的双波导微环耦合结构,利用传输矩阵法得到了透过率公式和相移公式。根据透过率公式,得到了随相移变化的非对称类Fano共振曲线。详细分析了各耦合区的透射系数对透过率曲线的影响,得知在t₁=t₂=t₃=0.2条件表现出的滤波特性比不带反馈的结构要好。在该条件下,微环和直波导的损耗系数都对透过率的影响比较敏锐,当损耗从0.8变到1时,透过率峰值几乎从0变到1。除此之外,透过峰附近的延迟系数达到29.1,所以该结构还可以用作光延迟     

Ultra-low Vpp and high-modulation-depth InP-based electro-optic microring modulator

A modulator is an essential building block in the integrated photonics,connecting the electrical with optical signals.The microring modulator gains much attention because of the small footprint,low drive voltage and high extinction ratio.An ultra-low Vpp and high-modulation-depth indium phosphide-based racetrack microring modulator is demonstrated in this pa-per.The proposed device mainly comprises one racetrack microring,incorporating a semiconductor amplifier,and coupling with a bus waveguide through a multimode interference coupler.Traveling wave electrodes are employed to supply bidirection-al bias ports,terminating with a 50-Ω impedance.The on/off extinction ratio of the microring reaches 43.3 dB due to the delic-ately tuning of the gain.An 11 mV Vpp,a maximum 42.5 dB modulation depth and a 6.6 GHz bandwidth are realized,respect-ively.This proposed microring modulator could enrich the functionalities and designability of the fundamental integrated devices.     

Linearized microring-loaded Mach-Zehnder modulator with RF gain

A linearized modulator based on the Mach-Zehnder interferometer (MZI) loaded with a second-order allpass microring resonator is proposed and analyzed. The device is shown to exhibit much smaller intermodulation distortion than standard Mach-Zehnder modulators, thus greatly enhancing the device dynamic range. Gain effect associated with the microring resonance results in a modulator transfer function with high slope efficiency and large RF gain. Moreover, combined with the use of a highly electrooptic polymer, the high slope efficiency allows for the possibility of realizing modulators with subvolt drive voltage. The detrimental effect of loss in the microring resonators on device performance is also investigated and a design approach to mitigate its effect is presented. The proposed modulator can be linearized to any arbitrary nth order by loading the MZI with a higher order allpass microring resonator.     

A Y-fed directional coupler modulator with a highly linear transfer curve

We demonstrated a linearized Y-fed directional coupler modulator in Z-cut LiNbO/sub 3/. The proof-of-concept device employed two electrode sections of opposite polarity whose lengths were chosen based on the results of our previous theoretical modeling. A highly linear modulation characteristic and improved tolerance to fabrication errors were achieved with a simple design, in excellent agreement with the theory. The linearity exceeded 90% over a wavelength range of 45 nm, centered around 1530 nm, with a maximum linearity of 97% at 1510 nm and a maximum modulation depth of 98%. By comparison, the linearity of conventional modulators is typically around 70%. Thus the device was proven to have a high linearity with a wide usable spectral range and relaxed fabrication tolerances.     

An electrooptic intensity modulator with improved linearity

A highly linear electrooptic modulator has been designed, fabricated, and evaluated. The design of this modulator consists of only a simple modification to the directional coupler. Two-tone testing has demonstrated that, for an optical modulation depth of 30% per channel, the third-order intermodulation distortion is more than 30 dB lower than that of the conventional directional coupler or Mach-Zehnder modulators. This improvement was not observed to be accompanied by any increase in second harmonic distortion. Also included are results of two-tone computer simulations which predict the improvement in linearity of this device for a range of modulation depths.<>     

基于石墨烯的光控太赫兹调制器

研究了锗基单层石墨烯结构宽带光控太赫兹调制器。利用实验室搭建的太赫兹时域光谱系统,实验证明了在1 550 nm飞秒光泵浦下,该太赫兹调制器工作带宽为0.2~1.5 THz。当泵浦光功率从0增加到250 mW时,该太赫兹波调制器的平均透过率从40%下降到22%,平均吸收系数从19 cm-1增加到44 cm-1,在0.2~0.7 THz,调制深度均高于50%,最大调制深度为62%（0.38 THz）。实验结果表明,相比于纯锗基太赫兹调制器,单层石墨烯的引入能增强对太赫兹波的调制效果。     

In search of a linear electrooptic amplitude modulator

An electrooptic modulator which offers high linearity and low intermodulation distortion (IMD) is proposed. The modulation characteristics, harmonic and intermodulation distortions, are calculated. In the two-tone test with an optical modulation depth of 16% for each channel, the third-order IMD is expected to be as low as -95 dB. Such a linearized electrooptic modulator used in conjunction with diode-pumped solid-state lasers can be expected to outperform directly modulated injection lasers for CATV transmission systems.<>     

Laser beam modulation using corner reflector and deep diffraction grating

A new scheme of the power modulator of laser beam is based on a corner-reflector unit with a relief diffraction grating that is placed on a plane of the unit and has a relief depth of several wavelengths of the laser radiation. It is shown that angular oscillations of the unit make it possible to implement modulation of the zero-order diffraction beam at a modulation depth of almost 100% and a relatively high linearity of the modulation characteristic that is reached at modulation depths of greater than 50%.     

Linearized Ring-Assisted Electrooptical Modulator for Coherent Optical OFDM Links

We present a design for a ring-assisted optical amplitude modulator based on a Mach-Zehnder interferometer with microring resonators coupled to each arm and characterized by improved linearity and dynamic range. We analyze the performance of the proposed device in a coherent optical orthogonal frequency-division-multiplexing system and show that it reduces the bit-error rate compared to conventional modulators.     

An analysis and a dynamic testing method of microwave QPSK modulation

Using the clockwise or anticlockwise stepping pulse code signal, the characteristics of general quaternary phase shift keying (QPSK) modulation are analysed. This paper gives the spectrums in several operational conditions and the admittance formulas of related two modulation circuits. Several typical examples of QPSK modulation are calculated. The modulation effect and the phase error can be decided and the QPSK modulator under the dynamic test may be adjusted by using above results. The experimental results are in agreement with the theoretical calculations. An X-band QPSK modulator is also presented. The maximum phase error is less than 4°, the phase accuracy near ±0.1°, the insertion loss less than 4 dB and the data (transfer) rate up to 68 Mb/s.     

Ultra-high-speed multiple-quantum-well electro-absorption opticalmodulators with integrated waveguides

Integrating the input and output waveguides with a multiple-quantum-well (MQW) electro-absorption (EA) optical modulator is shown to achieve ultra-high-speed modulation while keeping the total device length long enough for easy fabrication and packaging. Testing with fabricated modulators showed that a shorter modulation region results in a larger modulation bandwidth. The additional loss due to the waveguide integration was less than 1 dB. An optimized modulator showed a large modulation bandwidth of 50 GHz, a low driving voltage of less than 3 V, and a low insertion loss of 8 dB. A prototype module of this modulator had a bandwidth of greater than 40 GHz. Optimizing the MQW structure makes the modulator insensitive to polarization. These results demonstrate that MQW-EA modulators with integrated waveguides are advantageous in terms of fabrication, packaging, and ultra-high-speed modulation