Polymeric digital optical modulator based on asymmetric branch

A digital optical modulator based on an asymmetric Y-branch waveguide is proposed and fabricated by using an electro-optic polymer. The operating point is initially shifted to the off-state utilising the asymmetry in the branch to provide an initial zero-state with no electrical bias. It has been confirmed that the high extinction ratio can be obtained with a low drive voltage. An extinction ratio of 25 dB is demonstrated for a drive voltage of 20V using a polymer PMMA-DR1 with r_ss of 5 pm/V at 1.3 μm     

非对称马赫-曾德尔干涉型低串扰聚合物光开关

针对对称马赫-曾德尔干涉(MZI)型光开关工艺制备中形成的光栅结构所引起的导模与辐射模耦合是恶化光开关串扰特性的一个重要因素,提出一种采用非对称的MZI结构来抑止光栅导模和辐射模间耦合的新型聚合物电光开关设计方案。研究结果表明,光开关的串扰可以从-20dB改善到-50dB以上;同时,器件的开关电压也从传统MZI型结构开关电压的1.5Vπ减小到了1.0Vπ。     

全光纤粗锥MZ级联PCF-FP结构双参数特性研究

为了在测量NaCl溶液浓度的同时实现对温度的监测,提出了一种基于马赫-曾德干涉仪（Mach-Zehnder Interferometer,MZI）级联法布里-珀罗干涉仪（Fabry-Perot Interferometer,FPI）的干涉型传感器。在单模光纤上通过熔融放电制作出一对腰锥直径155 m、间隔1.5 cm的MZI,其对比度为10 dB、周期29.85 nm;在MZI尾纤的一端与光子晶体光纤（Photonic Crystal Fiber,PCF）相对熔接并在距熔接点176 m处将PCF切平,形成对比度为8 dB、周期为5.71 nm的FPI。实验选取1 535~1 555 nm波段MZI和FPI的干涉波谷特征波长,在0~150℃的温度和0%~24%的NaCl溶液浓度变化范围内测得MZI的温度和折射率灵敏度分别为50 pm/℃和9.97 nm/RIU,线性度均大于0.97;而FPI的波谷特征波长对折射率不敏感,温度灵敏度约为8.3 pm/℃,线性度为0.98。最后,通过构建温度-浓度函数关系矩阵得出了对温度和NaCl溶液浓度的灵敏度矩阵。该干涉型传感器对温度和NaCl溶液浓度表现出良好的灵敏度和线性度,可实现上述双参数的同时测量。     

High-input-power saturation properties of apolarization-insensitive semiconductor Mach-Zehnder interferometer gateswitch for WDM applications

We propose that a polarization-insensitive Mach-Zehnder interferometer (MZI) switch is useful for optical gate elements, especially if multiwavelength signals are input. This device has high-input-power saturation properties, which shows that both the operating voltage and the extinction ratio do not change when the optical input power reaches at least +18 dBm. A high extinction ratio of 30 dB was achieved in the wide-wavelength range of 20 nm. Moreover, the extinction ratio can be improved by up to 45 dB by using a cascaded configuration to decrease crosstalk. These results indicate the MZI gate switch is well suited to wavelength-division multiplexing (WDM) network components     

A research on the characteristics of an interleaver with a symmetrical resonator

In order to improve the transmission performance of the conventional Mach-Zehnder interferometer (MZI), a novel interleaver combining an "8"form ring resonator with a planar 3×3 single fiber coupler is proposed. Based on the phase modulation provided by the ring resonator, a flat filtering response is obtained by optimizing the coupling angle of resonator. The output expression is derived and numerical simulation is performed. The simulation indicates that the 0.5 dB passband and 25 dB stopband of the proposed interleaver are simultaneously improved remarkably, which are much wider than those of the single-stage MZI and the two-stage MZI interleavers, and the filtering performance of the proposed interleaver, which achieves a nearly square spectrum response, is also much better. Compared with the interleaver based on an asymmetrical MZI with a resonator in one arm, there is no difference between the intensities of two coherent beams in the condition of considering the influence of the propagation loss. Theoretical analysis shows that the influence of the propagation loss on extinction ratio can be effectively reduced.     

Compact polarization-independent Mach-Zehnder space switch combining carrier depletion and the quantum confined Stark effect

We have developed an n-doped InGaAs-InAsP quantum well between InP, which is suited for a polarization-independent Mach-Zender interferometric (MZI) space switch operating at 1.55 /spl mu/m. The InAsP is compressively strained and the InGaAs is tensile strained for polarization independence and for strain balancing. The important boundary condition for the design of this structure is the waveguide loss, which we limit to 0.6 dB/cm, and the crosstalk due to imbalance in the MZI, which we limit to <-30 dB. To reduce the size of the phase shifting region, while imposing this boundary condition, we combine the quantum confined Stark effect (QCSE) effect and the carrier-depletion effect by using an n-doped quantum well. The QCSE was first optimized for an undoped InGaAs-InAsP quantum well. A polarization independent /spl Delta/n of 7.8/spl middot/10/sup -4/ at 100 kV/cm was obtained at the expense of 0.2-dB/cm excess waveguide loss and 0.1-dB/mm electroabsorption loss. The carrier-depletion effect in a 2/spl middot/10/sup 11/cm/sup -2/-doped QW increases /spl Delta/n with a factor 2.6 to 2/spl middot/10/sup -3/, at the expense of 0.4-dB/cm free-carrier absorption-induced waveguide loss. The combination of the QCSE and carrier depletion results in a phase-shifter length of 0.46 mm for an MZI in push-pull configuration.     

级联FPI-MZI复合干涉光纤传感器双参数特性研究

为了实现工业生产过程中温度和溶液质量分数的同时测量和传感检测, 提出了一种由法布里-珀罗干涉仪(FPI)和马赫-曾德尔干涉仪(MZI)级联干涉结构构成的双参数传感器。该传感器由融合在一起的单模光纤(SMF)和空芯光纤(HCF)组成。采用同时测量FPI反射光谱和MZI透射光谱的特征波长位移的方法, 获得了FPI和MZI对温度和折射率的灵敏度差, 建立了传感器温度-质量分数灵敏度矩阵, 实现了传感器双参数的测量。结果表明, 在40℃~150℃的温度范围内, FPI的温度敏感度为10pm/℃, 而MZI的对温度不敏感; 在质量分数0.05~0.40的范围内, FPI对折射率不敏感, 而MZI质量分数灵敏度是232.3nm/RIU; 该传感器可以实现温度与溶液质量分数的同时测量。该研究为石油、化工、电力、钢铁、机械等加工行业中双参数的动态测量提供了参考。     

Spreading-resistance temperature sensor on silicon-on-insulator

A spreading-resistance temperature (SRT) sensor is fabricated on silicon-on-insulator (SOI) substrate and achieves promising characteristics as compared with similar SRT sensor on bulk silicon wafers. Moreover, experimental results show that the maximum operating temperature of thin-film (1.2 μm) SOI SRT sensor can reach 450°C, much higher than 350°C of thick-film (10 μm) SOI SRT sensor under the same current level. With complete oxide isolation, this sensor structure can be potentially used in low power integrated sensors operating at temperatures as high as 450°C     

一种双微环辅助马赫 曾德尔干涉仪滤波器

为改善普通马赫-曾德尔干涉仪(MZI)滤波器的输出性能,采用将双微环谐振器与马赫-曾德尔干涉仪相结合,设计出一种新的滤波器结构.采用信号流程图理论分析得出该结构的传递函数,并对输出端口的透射谱进行数值模拟分析.仿真结果表明,与普通马赫-曾德尔干涉仪滤波器相比,当选择合适的耦合系数,双微环谐振器辅助马赫-曾德尔干涉仪滤波器的透射谱顶部平坦,形状类似于方形,自由光谱范围达到了19 nm,锐度因子为1.16,消光比为54 dB,品质因子为94.5,滤波性能得到较大改善.详细研究了耦合系数和微环半径对滤波器输出性能的影响.     

A High Dynamic Range CMOS Image Sensor With Inpixel Light-to-Frequency Conversion

A high dynamic range CMOS image sensor with inpixel light-to-frequency conversion has been designed. The prototype chip was fabricated in a standard 0.18-mum single-poly six-metal CMOS technology. The experimental results show that, operating at 1.2 V, the sensor can achieve a linear dynamic range of over 115 dB and an overall dynamic range of over 130 dB     

Integrated optical Mach-Zehnder biosensor

We present measurements on biomolecular surface multilayers using an integrated optical sensor based on the Mach-Zehnder interferometer (MZI). The sensor design is unique in that it incorporates a three-waveguide coupler structure at the interferometer output which gives advantages in terms of signal referencing and in establishing and maintaining a sensitive operating point. The sensor performance is characterized with respect to bulk superstrate index and by the formation of multiple protein adlayers using a biotin-avidin-based biochemical system. The detection limit for protein loading is estimated as 5 pg/mm²     

Single-mode operation of 1.55 ?m semiconductor lasers using a volume holographic grating

A volume holographic grating in iron-doped lithium niobate has been demonstrated as a novel infra-red selective filter to produce stable single-mode output from a semiconductor laser operating at 1.55 ?m. Preliminary results show that a ~16 dB adjacent-mode rejection ratio can be obtained.     

High tolerances for a low-voltage, high-contrast, low-insertion-loss asymmetric Fabry-Perot modulator

The authors report on the reduction of the operating voltage of a GaAs/AlGaAs multiple-quantum-well asymmetric Fabry-Perot modulator to approximately 4.2 V for a high-contrast ( approximately 15 dB), low-insertion-loss ( approximately 3 dB) device. This improvement on modulator performance makes the device suitable for a practical system and has been accomplished by an increase of the front reflectivity to approximately 43%. The authors discuss general design issues and show that the higher finesse cavity does not have to lead to low fabrication and environmental tolerances. On the contrary, this device's tolerance to fabrication and environmental factors is expected to have been improved.<>     

Linear and quadratic electrooptic effects in symmetric andasymmetric quantum-well structures

In the first part of the paper, the changes in the complex index of refraction of quantum-well structures proportional to the applied dc electric field (F) and its square are obtained from stationary perturbation theory. Expressions are obtained for the linear and quadratic changes in index and absorption coefficients of asymmetric and symmetric quantum well structures. The triple resonance term does not contribute to the quadratic Kerr effect for a symmetrical well in an expansion about F=0. In the second part of the paper, these results are applied to several types of modulators. First we consider two kinds of silicon/silicon-germanium high-barrier asymmetric quantum well structures at 1.55 μm. For the step well, the dominant triple resonant term of the quadratic Kerr effect adds to the linear electrooptic effect (LEG) to yield an intensity extinction ratio of 15 dB in switching from F=+8 V/μm to -8 V/μm and a very small insertion loss of 0.04 dB, for a modulator length of 200 pm and for narrow linewidths (FWHM=7.6 meV). For the case of asymmetric barriers confining silicon wells, a comparable insertion loss is obtained but with an extinction ratio of 44 dB for FWHM=20 meV, a clearly superior performance. For symmetrical silicon-based wells, the double-resonance modulation, though small at λ=1.55 μm, is appreciable at λ=10.6 μm. For the Kerr effect in symmetrical gallium arsenide wells at λ=10.6 μm reported by Sa'ar et al., we show that it is the double-resonance term which yields the six order-of-magnitude enhancement with respect to bulk and that an even larger enhancement of the Kerr effect can be obtained in an asymmetric GaAs structure together with the LEO     

Active magnetic field sensor for measurements of transients

An active magnetic field sensor consisting of an electrically small loop, two ferrite core transformers, and a balanced amplifier with a low input impedance is suitable for measurements of fields, in a broad range of frequencies, and transients. The sensor provides a flat transfer function from approximately 600 Hz to 200 MHz (3 dB roll-off frequencies) and high-fidelity reproduction of pulses with a risetime of 2 ns. The sensor can be used to measure fields from less than 0.2 mA/m to approximately 0.2 A/m. The sensor has a minimal response to the electric field (at least -20 dB). The sensor's dimensions are 6 cm×6 cm, and the electronic circuitry is contained in a box of approximately 5 cm×8 cm×3 cm     

Monolithically integrated InGaAs-AlGaInAs Mach-Zehnder Interferometer optical switch using quantum-well intermixing

A highly efficient monolithically integrated Mach-Zehnder interferometer (MZI) optical switch based on a 1.5-/spl mu/m InGaAs-AlGaInAs multiple-quantum-well structure is reported. The device was fabricated by integrating phase shifter sections with bandgap-shifted low-loss waveguides obtained by a single step sputtered SiO/sub 2/-annealing quantum-well intermixing technique. Evaluation of the refractive index change induced by current injection (plasma, band-filling, band-shrinkage effects) and applied electric field (quantum confined Stark effect) based on the MZI was investigated. A device with an active length of 400 /spl mu/m in one of the MZI arms had an extinction ratio /spl ges/20 dB with a half-wavelength current (I/sub /spl pi//) and half-wavelength voltage V/sub /spl pi// as low as 3.2 mA and 3.5 V (1.9 V in push-pull configuration), respectively.     

基于标准CMOS工艺的光敏传感单元结构的研究

基于0.6μm标准N阱CM O S工艺,研究了光敏管的结深及其侧墙结构对有源感光单元的感光面积百分比、光电响应信号幅值、感光灵敏度以及感光动态范围等参数的影响。研究了包括传统N+/P衬底的光敏管结构,以及网格状N+/P衬底,N阱/P衬底,网格状N阱/P衬底,P+/N阱/P衬底的光敏管结构。测试结果表明,不同深结深的光敏管结构,可以将器件感光灵敏度提高8~16.5 dB;网格状光敏管结构可以增加光敏管的侧墙面积,改善器件感光灵敏度;非网格状光敏管结构具有较低的暗电流和较大的感光动态范围,其中P+/N阱/P衬底光敏管结构的传感单元在变频两次扫描的工作方式下的感光动态范围可达139.8 dB。     

一种高线性度非对称单刀双掷开关的设计

介绍了一种用于射频收发系统的16 GHz、低损耗、高隔离度、高线性度的非对称型单刀双掷开关。针对串联和并联晶体管尺寸对插入损耗及隔离度的影响、对称型和非对称型两种结构各自的特点,以及选择非对称结构的原因进行了分析。采用90 nm CMOS工艺实现,设计中采用深N阱MOS管,并在必要的节点加入交流悬浮偏置,提高开关整体性能。测试表明,Rx模式下,插损为0.77 dB,隔离度为22.9 dB,输入1 dB压缩点为9 dBm;Tx模式下,插损为2.14 dB,隔离度为20.2 dB,输入1 dB压缩点大于15 dBm。     

用于SiGe HBT LNA的新型双有源偏置电路的设计

偏置工作点是影响低噪声放大器(LNA)线性度的因素之一.为了保证LNA能够更好地对信号进行线性放大,稳定的偏置工作点对于放大器来说显得尤为重要.提出了一种新型有源偏置技术,通过同时采用两个电流源为LNA提供直流偏置,以达到稳定放大器偏置工作点的目的.基于JAZZ 0.35 μm SiGe工艺,采用该新型双有源偏置技术,设计了一款LNA.在1.8～2.2 GHz频带时,放大器的增益为22.03±0.46 dB,噪声系数小于3.7dB,2.0 GHz时的输入3阶交调点(IIP3)为5 dBm,相对于传统无源偏置的LNA提高了10 dBm.仿真验证了该新型有源偏置技术对提高LNA线性度的有效性.     

Tunable fiber laser based on a cascaded structure consisting of in-line MZI and traditional MZI

A tunable erbium-doped fiber (EDF) laser with a cascaded structure consisting of in-line Mach-Zehnder interferometer (MZI) and traditional MZI is proposed. The transmission spectrum of the in-line MZI is modulated by the traditional MZI, which determines the period of the cascaded structure, while the in-line MZI’s transmission spectrum is the outer envelope curve of the cascaded structure’s transmission spectrum. A stable single-wavelength lasing operation is obtained at 1 527.14 nm. The linewidth is less than 0.07 nm with a side-mode suppression ratio (SMSR) over 48 dB. Fixing the in-line MZI structure on a furnace, when the temperature changes from 30 °C to 230 °C, the central wavelength can be tuned within the range of 12.4 nm.