缓冲质子源LiNbO3波导折射率计算及实验

为实现铌酸锂退火质子交换(APE)波导折射率分布的准确计算,选择含苯甲酸锂的苯甲酸缓冲液作为质子交换质子源,高温退火制作了波导样本.针对该工艺过程建立退火质子交换波导模型,包括非线性扩散模块和光学数值仿真模块,分别计算APE波导折射率及其模式有效折射率.以测得的样本波导模式有效折射率和计算的有效折射率差的均方根构建评价函数(FOM),结合遗传算法提取该工艺条件下质子扩散参数,实现了不同交换深度和退火时间波导折射率分布及其光学特性的一体化计算.实验表明:FOM小于0.001,计算折射率分布同IWKB方法测得结果吻合较好,最大偏差约0.002.     

不同切型质子交换弯曲波导的弯曲损耗研究

退火质子交换铌酸锂光波导是一类重要的光波导。对2种不同切型的3种常用S形弯曲质子交换光波导,利用宽角有限差分光束传播法进行了分析。结果表明,3种弯曲波导的弯曲损耗,随波导结构参数的变化基本上是相同的,而在相同的波导结构参数下,X切型的质子交换光波导的弯曲损耗总体上都要小于Z切型的质子交换光波导。数值计算结果为相应波导器件的设计和制备提供了一定的参考。     

高速硅基单端推挽驱动狭缝脊波导调制器

针对硅基单端推挽驱动调制器的脊波导pn结部分结电容较大,限制了调制器带宽进一步提高的问题,提出了一种狭缝脊波导pn结结构。通过将脊波导pn结蚀刻一定尺寸的狭缝,降低了pn结电容,实现了带宽的提升。对两种pn结进行了仿真对比,结果表明,在相同电极结构与掺杂条件下,狭缝脊波导调制器比脊波导调制器的电光带宽提升了约8.3 GHz。基于优化的单端推挽驱动狭缝脊波导调制器,仿真实现了90 Gbit/s的OOK信号调制,眼图消光比为14.69 dB。     

铌酸锂退火质子交换光波导的有限元法分析

本文用有限元(Ｆｉｎｉｔｅ Ｅｌｅｍｅｎｔ Ｍｅｔｈｏｄｓ－ＦＥＭ)的数值计算方法分析了铌酸锂晶体中的退火质子交换(Ａｎｎｅａｌｅｄ Ｐｒｏｔｏｎ Ｅｘｃｈａｎｇｅｄ－ＡＰＥ)光波导,并给出了对应于不同退火时间的铌酸锂光波导的有限元精确数值分析结果．     

聚合物电光波导调制器中微带电极的几何参数对重叠积分的影响

本文对有机聚合物导调制器的重叠积分进行了详细计算，着重讨论了器件的几何参数对重叠积分的影响。     

High-speed shielded velocity-matched Ti:LiNbO3 opticalmodulator

A shielded velocity-matched Ti:LiNbO₃ optical modulator is investigated, focusing on the characteristics of the traveling-wave (TW) electrode and the optical waveguide. The optical waveguide is analyzed and its parameters are determined using the newly developed modified-step-segment method (MSSM). The TW electrode is analyzed using the second-order triangular element quasi-TEM finite element method (FEM). By taking the thickness of the coplanar waveguide (CPW) traveling-wave (TW) electrode into consideration, it is confirmed that there is an optimum overlaid layer thickness for a given electrode thickness. It is also shown that very wide modulation bandwidth can be attained by using the optimum CPW TW electrode thickness and overlaid layer thickness     

倒相结构波导电光器件中微带电极的比较和优化

对共平面波导电极（ＣｏＰｌａｎａｒＷａｖｅｇｕｉｄｅｅｌｅｃｔｒｏｄｅ，简称ＣＰＷ）和非对称微带电极（ＡｓｙｍｍｅｔｒｉｃＳｔｒｉｐＬｉｎｅｅｌｅｃｔｒｏｄｅ，简称ＡＳＬ）用于行波型例相电极结构电光波导器件的调制特性进行了分析，并给出电极特征参数和频率响应数值计算结果，比较表明将ＡＳＬ电极用于倒相结构的器件对在高频波段实现有效的光调制仍十分有效。     

聚合物波导电光调制器

尽管直接调制激光二级管控制光波是一种简单是一种简单且重要的调制方式，但光波导结构的调制器将使器件性能得到惊人的改善，本文简略介绍了聚合物波导电光调制器，并给出了制备该器件的聚合物材料及制备过程。     

量子密钥分发系统中的相位调制器特性分析

在量子密钥分发系统(QKD)中,LiNbO3波导相位调制器是构成单光子干涉仪的关键器件。文章阐述了LiNbO3相位调制器的相位调制特性、偏振特性及其对量子密钥分发系统的影响,介绍了退火质子交换工艺制备的线性单偏振LiNbO3相位调制器与采用钛内扩散工艺制备的低偏振相关损耗(PDL)LiNbO3相位调制器的性能指标。     

SOA-Assisted Data-Polarization-Insensitive Wavelength Conversion in a PPLN Waveguide

We demonstrate a novel method of wavelength conversion in a periodically poled lithium niobate (PPLN) waveguide using polarization modulation and amplitude modulation of its pump. Polarization-insensitive, all-optical, intensity-to-polarization conversion in a semiconductor optical amplifier (SOA) is used to reduce the waveguide's polarization sensitivity from >30 dB to <1 dB. We demonstrate BER measurements of the converted signal at 2.5 Gb/s. We also demonstrate polarization modulation of the PPLN waveguide pump using cross-polarization modulation in highly nonlinear fiber (HNLF) at 10 Gb/s.     

硅包层质子交换条形光波导的频率响应

退火质子交换工艺已成为一种制备低损耗铌酸锂光波导的重要技术.但目前对该类光波导传输特性的研究还不多.利用半矢量光束传播法,对硅包层X切退火质子交换铌酸锂条形光波导的频率响应特性进行了数值分析.给出了几种波导结构参数下的计算结果.结果表明,波导传输模式的衰减特性与波长相关.波导的衰减特性,可以通过调整波导表面中心处折射率增量,硅包层厚度,及缓冲层的折射率和厚度来控制.硅包层光波导可以用来制作光频滤波器.     

High-Speed X-Cut Thin-Sheet LiNbO3 Optical Modulator With Folded Structure

We propose a small-footprint X-cut thin-sheet lithium niobate optical modulator with high-speed and low-driving-voltage characteristics. Since an optical waveguide is folded by a mirror placed at one edge of the modulation chip, the chip can be shortened by about half. In addition, a wide modulation bandwidth can be achieved, because the path-length difference between the optical waveguide and the coplanar-waveguide (CPW) electrode is decreased to as short as possible by placing the CPW electrode as far as possible along the optical waveguide in the folded portion, and the microwave effective index is set to realize effective velocity matching between the lightwave and the microwave. A small footprint of 1.78 times 29 mm, a low half-wave voltage of 2.0 V at dc, and a 3-dBe modulation bandwidth of 20 GHz were obtained.     

Microphony in Waveguide

This paper describes the mechanism of phase modulation by waveguide in the presence of a high intensity acoustic field. X-band rectangular was studied to determine the following: a) Resonant frequency in a transverse vibrational mode. b) Means of minimizing phase modulation.     

Hybrid Electrodes Used in Polymer Electro-Optic Modulator with Ultra-Broadband

Hybrid electrode combined coplanar waveguide (CPW) and microstrip lines in ultra-broadband electro-optic modulators. The characteristics of the modulators with hybrid electrode is like that of the modulator with the microstrip lines, in which the microstrip electrode is loaded above only one arm of Mach-Zehnder (M-Z) optical waveguide, besides the problem of microstrip line to coaxial transition and corona polarization in polymer modulators have been best solved at the same time. By using finite element method (FEM), the characteristic parameters such as half-wave voltage, modulation bandwidth characteristic impedance, effective microwave refractive index of polymer modulators with microstrip line and hybrid electrode are analysed and compared in this paper. The results present that velocity match, impendence match and lower microwave propagating loss is easily realized in modulators with hybrid electrode.     

Characterization of annealed proton exchanged LiNbO3waveguides for nonlinear frequency conversion

A thorough and detailed characterization of annealed proton-exchanged (APE) waveguides in Z-cut LiNbO₃ is described. The mode index measurements in planar waveguides as a function of wavelength and annealing time are reported, including useful analytical relations for the refractive index change, its dispersion, and the depth profile as a function of annealing parameters. Analytical expressions for the mode propagation characteristics are presented and experimentally verified with reasonable accuracy. It is shown that the planar waveguide characterization results can be used to model the channel waveguide characteristics accurately. The model provides closed-form expressions for the mode index and the mode field profile, and the theoretical results are in excellent agreement with the measured data. The technique is used to accurately predict the phase mismatch between the fundamental and second harmonic modes in frequency-doubling experiments using APE channel waveguides. An optimum waveguide geometry for which the phase mismatch is relatively insensitive to the waveguide nonuniformity was predicted and verified experimentally     

Waveguide devices based on active metallic photonic crystals

We present a detailed analysis of waveguide devices patterned in two- and three-dimensional metallic photonic crystals. Tuning of guiding properties of electromagnetic waves is induced by a reflectivity modulation of waveguide walls by means of active electronic devices inserted in the 2D lattice. Such an active waveguide acts as a phase shifter in monomode operation as a consequence of the tunable capacitive coupling afforded by the 3D lattice. On this basis, various operating modes of multiport waveguide devices are investigated: (i) a switching operation in a T-shaped structure, (ii) highly directional lateral transfers in a multimode branch line coupler.     

Analysis and Demonstration of Mach–Zehnder Polymer Modulators Using In-Plane Coplanar Waveguide Structure

Analysis, design, and experimental demonstration of polymer Mach-Zehnder (MZ) modulators with a newly proposed in-plane coplanar waveguide (CPW) electrode are presented in this paper. Compared to the conventional CPW electrode, the new in-plane CPW configuration significantly enhances the overlap factor between microwave and optical wave by 40% from the theoretical calculations. Different from polymer modulators using the traditional microstrip electrodes, this structure can suppress dc bias voltage drift and widen modulation bandwidth. Using CLD1/APC and AJL8/APC electrooptic polymers, MZ modulators using the in-plane CPW are fabricated and tested. The measured Vpi's of the MZ with 15-mum gap spacing and 2 cm electrode length are 5.4 and 9.5 V at 1.55 mum for the AJL8/APC and CLD1/APC devices, respectively. The evaluated Upsi₃₃'s are 46 pm/V for the AJL8/APC and 26 pm/V for the CLD1/APC MZ. The dc bias stability is tested and compared for both the microstrip and the in-plane CPW electrode modulators. Experimental results show that the in-plane CPW modulator greatly improves the bias stability. From the microwave measurement, the microwave signal loss of the modulator using the in-plane CPW is much reduced to 0.2 dB/cmradicGHz, while 0.7 dB/cmradicGHz using the microstrip.     

Y波导调制器残余强度调制的测量

为了便于分析Y波导调制器残余强度调制的产生机理,提出一种Y波导调制器残余强度调制的测试方法.系统采用Spartan-6系列的FPGA作为主控芯片,控制模数转换芯片ADS5560对经光电转换后的调制光信号进行采集,将采集到的数据打包后通过UART通信模式发送至PC机,获取Y波导调制器残余强度调制大小及波形信息.根据残余强度调制大小和波形信息分析模场改变引起的线性和杂散光与输出光的干涉两种机理产生的残余强度调制所占比例.测试结果表明,系统稳定性良好,对于Y波导调制器的开发有重要意义.     

光纤聚合物电光调制器电极对波导特性的影响

有机聚合物高速电光调制器是全光纤器件,插入损耗低,集成度高,能极大地降低模式失配和调制电压,提高调制效率,是未来超长距离超大容量高速光通信系统中的关键器件之一。将一种基于长周期光纤光栅的光纤聚合物电光调制器看作5层均匀圆光波导,考虑两层电极及其复折射率的实际情况,利用紧致的超格子方法,在复数域分析这种光纤聚合物电光调制器的波导特性。从模式折射率的实部和虚部、模场分布等角度对数值计算结果进行分析表明,只忽略外电极对调制器的波导特性影响很小,考虑电极时长周期光栅的谐振波长比不考虑电极时大,从而影响调制特性。     

High-Speed Coplanar Waveguide Based Submount for 40 Gbit/s Electroabsorption Modulator

A high-speed submount has been designed and fabricated for 40 Gb/s electroabsorption (EA) modulators. The submount contains a coplanar waveguide (CPW) for microwave signal feeding and a Ta₂N thin-film resistor for impedance matching. The CPW transmission line is designed to ensure low microwave loss and reflection, and Ti/Cu/Ni/Au metal is adopted for electrode fabrication to guarantee good contact with the Ta₂N thin-film. The typical reflection coefficient of fabricated submount is estimated to be lower than?21 dB up to 40 GHz. As a demonstration, a high-speed EA modulator was chip-level packaged using the high-speed submount, and the measured small-signal modulation bandwidth was over 40 GHz.