具有双电光分子的聚合物型太赫兹波探测器件

与传统的无机晶体材料相比,电光聚合物材料具有更高的电光系数,并且没有声子吸收问题,由此构成的太赫兹波探测器件具有更高的效率和带宽。但是侧基型和主客体型的电光聚合物具有电光系数偏低和相分离问题,这些缺点限制了这类材料的应用。具有双电光分子的聚合物材料可以克服上述问题,利用这种材料构成共面插指结构的太赫兹波探测器件效率可提高80%,带宽可扩展到9THz,并且器件具有良好的稳定性。     

一种新型VLSI电路外部电光探测器北大核心CSCD

采用极化聚合物电光材料,设计制作出一种结构新颖的亚微米VLSI电路正面入射式外部电光探测器。通过在探测器中引入参考电极,实现了电压的标定测量;利用1μm线宽指状电极的电场分布,验证了触立式极化聚合物电光探测器对电场具有较高的空间分辨率。实验证明,该新型外部电光探测器的空间分辨率可达0.5μm,完全满足亚微米电路无损探测的要求。     

一种新型VLSI电路外部电光探测器

采用极化聚合物电光材料,设计制作出一种结构新颖的亚微米VLSI电路正面入射式外部电光探测器.通过在探测器中引入参考电极,实现了电压的标定测量;利用1 μm线宽指状电极的电场分布,验证了触立式极化聚合物电光探测器对电场具有较高的空间分辨率.实验证明,该新型外部电光探测器的空间分辨率可达0.5 μm,完全满足亚微米电路无损...     

电光聚合物波导的设计制作及其在光集成中的应用探索

相对于无机材料和半导体而言,极化电光聚合物具有无法比拟的优点响应速度快、介电常数低、调制带宽大、透光波段宽、制备简单、易于集成、成本低廉等.基于电光聚合物的波导器件因其在全光网中的关键作用而越来越引起人们的重视.本文从分析电光聚合物的特性开始,讨论利用高电光系数的聚合物材料设计和制作电光聚合物波导及在工艺中应注意的一些关键问题,介绍了电光聚合物波导器件的应用,其性能和成本优势使其在全光网中具有广阔的应用前景.     

实现光强精细调制的共轭聚合物波导电光调制器

提出了一种新型的聚合物波导电光调制器,同时利用了聚合物材料的Pockels效应和Kerr效应,在不增加调制电压的情况下,通过引入直流偏压增加了调制器的调制度,调制深度随着直流偏压的增加而增加。采用峰-峰值9.9V的调制电压、100V的直流偏压,利用pockels电光系数γ33仅为4.052×10-14 m/V和二次电光系数S33为6.889×10-21 m2/V2的聚合物材料制备了波导电光调制器,实现了7.54%的调制度。如果采用具有更高的分子极化率及电光系数的非线性共轭聚合物材料,可期待在更低的直流偏压和工作电压情况下,得到更高的调制深度。调制器的工作面积大,可以实现大面积光斑的调制。本文的聚合物波导电光调制器适用于激光脉冲喷丸强化与成形技术,通过调整调制器的直流工作偏压,能够实现激光光斑能量的精细调节。     

聚合物偶极子天线型光纤电场传感器

设计并初步成功制作了聚合物光纤电场传感器.假设聚合物材料的电光系数r13=10 pm/V,设计的两种电场传感器的半波电场Eπ=36.2和15.8 kV/m.用自制的二阶非线性光学聚合物BPAN-NT作为聚合物光纤电场传感器的芯层材料,制作了电光调制器.用反应离子刻蚀的方法制作脊形光波导,通过电晕极化使芯层具有电光效应,...     

聚合物光波导器件的最新进展

由于有机聚合物材料具有介电常数小、电光和热光系数大、热损耗小、易于加工及可垂直集成等优点,聚合物波导器件成为近几年研究的热点。本文在介绍光学聚合物材料优点和一些新型聚合物的基础上,重点讨论了聚合物波导器件的最新进展。     

基于π型结构的光电探测器功率合成阵列北大核心

针对ROF(光载无线通信)基站需要高功率大带宽光电探测器的问题,提出π型光电探测器阵列功率合成电路。通过将探测器嵌入在用电感互连的人工传输线上,即按照阵列式结构将单个π型光电探测器电路组合起来构成所需电路,实现功率合成,从而得到高功率大带宽的信号。电路首尾支路级联两个二极管来降低等效结电容以达到电路的最佳阻抗匹配。仿真结果表明,π型光电探测器阵列能在保持大带宽的同时对各级光电二极管功率进行有效地合成,相比于同级的行波探测阵列合成效率更高。     

聚合物光波导器件的最新进展

由于有机聚合物材料具有介电常数小、电光和热光系数大、热损耗小、易于加工及可垂直集成等优点，聚合物波导器件成为近几年研究的热点．本文在介绍光学聚合物材料优点和一些新型聚合物的基础上，重点讨论了聚合物波导器件的最新进展．     

基于M-Z光纤干涉仪测量极化聚合物的电光系数

提出了采用Mach Zehnder(M Z)光纤干涉仪的电光聚合物电光系数测量方法,对其测量原理进行了分析,研究了光纤干涉仪的臂长差、样品的插入损耗对系统可见度的影响,讨论了通过合理设置耦合器的耦合系数提高系统测量性能的方法。系统具有较好的稳定性和较高的灵敏度,既适合于聚合物薄膜也适合于聚合物波导的测量,系统干涉可见度为0.86,可分辨的最小相位变化约为6×10-6 rad。该系统可以同时测量2个独立的电光系数γ13和γ33,使用该系统测得一种有机/无机杂化材料ASD/SiO2 TiO2 极化后的电光系数为γ13=0.72±0.01 pm/V和γ33=2.8±0.01 pm/V。     

Highly Efficient and Thermally Stable Electro‐Optical Dendrimers for Photonics

After a brief review on electro‐optical (EO) polymers, the recent development of EO dendrimers is summarized. Both single‐ and multiple‐dendron‐modified nonlinear optical (NLO) chromophores in the guest–host polymer systems showed a very significant enhancement of poling efficiency (up to a three‐fold increase) due to the minimization of intermolecular electrostatic interactions among large dipole moment chromophores through the dendritic effect. Moreover, multiple NLO chromophore building blocks can also be placed into a dendrimer to construct a precise molecular architecture with a predetermined chemical composition. The site‐isolation effect, through the encapsulation of NLO moieties with dendrons, can greatly enhance the performance of EO materials. A very large EO coefficient (r₃₃ = 60 pm/V at 1.55 μm) and high temporal stability (85 °C for more than 1000 h) were achieved in a NLO dendrimer (see Figure) through the double‐end functionalization of a three‐dimensional phenyl‐tetracyanobutadienyl (Ph‐TCBD)‐containing NLO chromophore with thermally crosslinkable trifluorovinylether‐containing dendrons.     

High performance electro-optic modulator based on thin-film lithium niobate

Electro-optic (EO) modulator plays a very critical role in the optical communication systems. Here, we report a stimulated thin-film lithium niobate (LN) modulator with a half-wave voltage-length product of 1.8 V.cm, which can successfully achieve modulation and demodulation of a 1 GHz sinusoidal signal with an amplitude of 5 V in experiment. The optical loss caused by metal electrodes is reduced by optimizing the waveguide structure and depositing silica onto the waveguide, and group-velocity matching and characteristic impedance matching are achieved by optimizing the buffer silica layer and the electrode structure for larger bandwidth, which simultaneously improves the modulation efficiency and bandwidth performance. Our work demonstrated here paves a foundation for integrated photonics.     

探测光波长对太赫兹波电光取样探测技术的影响

由于太赫兹波电光取样探测技术中电光晶体存在的色散关系, 探测光的波长会直接影响到电光取样的探测带宽和效率.由于该色散关系的存在, 不同的电光晶体在电光取样中响应函数不同.本文研究了两种典型的电光晶体-碲化锌和磷化镓晶体的响应函数, 发现在选取的四种探测激光波长内(600 nm、800 nm、1200 nm、1600 nm), 800 nm的探测激光更合适碲化锌晶体, 1200 nm的激光更合适磷化镓晶体.对于不同厚度的晶体, 存在一个最优化的探测激光波长, 使得该晶体的电光响应函数有最宽的带宽.     

Optical intensity modulators using diazo-dye-substituted polymerchannel waveguides

The electrooptic (EO) modulation of 1.32 μm laser light is measured in Mach-Zehnder channel waveguides fabricated with diazo-dye-substituted polymers with coplanar-waveguide (CPW) or microstrip (MS) electrodes. Two types of channel waveguide fabricated by photobleaching or O₂ reactive-ion etching (RIE) exhibit the same EO coefficients r₃₃ under the same poling condition. However, the photobleached waveguides show a lower half-wave voltage than the RIE-fabricated ones because of both the optical power concentration in a core layer and the existence of an EO active cladding layer. These tendencies are well explained by considering “effective” overlap integrals between the optical and electric fields, including the distribution of EO-active regions. The maximum r₃₃ value (26 pm/V) of the poled diazo-dye-substituted polymer is obtained with an RIE-fabricated MS-modulator     

Low-Noise and High-Frequency Resolution Electrooptic Sensing of RF Near-Fields Using an External Optical Modulator

We developed an electrooptic (EO) sensing system using an external optical intensity modulator for radio frequency (RF) electric near-field measurements. This low-noise, high-frequency resolution system is based on the photonic heterodyning technique in which a RF near-field signal is mixed with modulated light by an EO crystal and downconverted to the difference frequency. Because the optical modulator has a bandwidth extending from DC to several gigahertz, the frequency resolution of this system is determined by that of the RF synthesizer it uses. The intensity noise of the modulated light is quite low, and the noise level of the EO signal can be reduced to almost the shot-noise level by using a balanced detection scheme.     

Integrated optics components and devices using periodic structures

The selected research activities on integrated optics components and devices using periodic structures are reviewed, with emphasis on the authors' works employing the electron-beam writing technique. The periodic structures include static gratings and dynamic ones produced through acoustooptic (AO) and electrooptic (EO) effects. They provide a variety of passive functions and effective means for guided-wave control. The review is made from the integration point of view, including the most recent results. First, the theoretical fundamentals are outlined and the electron-beam writing techniques, including the writing system, are discussed. Next, passive components (grating deflectors, filters, lenses, couplers, etc.) and elements for guided-wave controlling and detecting (AO and EO grating elements and photodetectors) are described. Then, integrated optic devices, i.e., wavelength demultiplexers, RF spectrum analyzers, optical disk pickup, etc., are presented. Finally, the possibility of future applications is discussed.     

Electro-optic polymer-based modulator design and performance for 40 Gb/s system applications

We investigate the potential performance of polymer-based electro-optic (EO) modulators for high-speed systems at 40 Gb/s and beyond. General strategies and specific designs are presented to reduce the modulator half-wave drive voltage while maintaining a broadband response. In addition, we consider practical system requirements that may allow the relaxation of certain modulator design parameters to further improve performance. Designs are presented that may enable a 3-dB electrical bandwidth of 30 GHz with a single-ended half-wave drive voltage of /spl sim/1.6 V for 1.3-/spl mu/m light assuming an effective EO coefficient of 30 pm/V in the waveguide core.     

Environmental Stress Testing of Electro–Optic Polymer Modulators

Low $V_{pi}$ electro–optic (EO) polymer modulators were environmental stress tested at both the chip and packaged device level. Different top clad materials showed different results for high-temperature and temperature cycle testing, which is related mostly to coefficient of thermal expansion (CTE) mismatches and/or adhesion properties of the clads related to other materials in the devices stack and to the substrate and electrode materials. With thoroughly compatible cladding, devices that are thermally stable for over 5000 h at 85 $^{circ}$C have been achieved. High optical power ( 500 mW @ 1550 nm) tests showed the photochemical stability of the EO polymer material in hermetically sealed packages. The results demonstrate that clad polymers and interactions between devices layers are of concern for achieving environmentally stable EO polymers modulators.      

Optimal design of a high-speed polymer Mach-Zehnder interferometer electro-optic switch over 260 GHz

By using the proposed 3-D mode propagation analysis method and point-matching method, a polymer multimode interference (MMI) Mach-Zehnder interferometer (MZI) electro-optic (EO) switch is designed and optimized for enhancing the EO modulating efficiency and matching the impedance and the velocity. The designed switch possesses low driving voltages of ±1.375 V with a short EO active region length of 5 mm under 1550 nm wavelength, and the estimated cutoff switching frequency is up to 263 GHz due to the less mismatch between the lightwave velocity and microwave velocity. The 3-dB lightwave bandwidth is 60 nm, and within the wavelength range of 1520–1580 nm, the insertion loss and crosstalk are less than 6.71 and −30 dB, respectively.     

Generalized Greedy Broadcasting for Efficient Media-on-Demand Transmissions

To reduce the bandwidth of media-on-demand transmissions, different broadcasting techniques have been developed over the last years. For highly demanded media, proactive schemes have a lower bandwidth requirement compared to reactive ones. While some of the proactive schemes try to obtain an efficiency near to the theoretical limit, others have been developed to lower the bandwidth by partial preloading, additional playout delay, the use of breaks within the transmission or by exploiting bandwidth variations of variable-bit-rate media. In this article we describe how one of the most efficient proactive transmission schemes can further be improved and generalized so it supports all these additional enhancements and outperforms its predecessor and the specialized schemes.