硅-有机物材料混合电光调制器的优化设计

设计了一种基于绝缘上层硅的硅-有机物材料混合马赫-曾德干涉型高速电光调制器.利用光束传播法对顶层硅为220nm的绝缘上层硅基片上的3dB分束器/合束器的结构参数进行模拟,优化后附加损耗仅为0.106dB.为提高模式转换效率,在条形波导和slot波导之间设计了模式转换器,光耦合效率高达98.8%,实现了光模式高效转化.利用时域有限差分法模拟了slot波导平板区掺杂浓度对波导内光学损耗的影响,在几乎不产生光学损耗的情况下,得到平板区轻掺杂浓度为71017/cm3,调制器设计总损耗为0.493dB.利用薄膜模式匹配法对slot波导结构进行仿真分析,考虑slot区等效电容及平板区等效电阻对带宽的影响,优化后得到slot波导结构的限制因子为0.199.采用slot波导与强非线性有机材料LXM1结合的绝缘上层硅平台实现了强普克尔效应,得到电光调制器半波电压长度积为1.544V·mm,电学响应3dB带宽为137GHz.     

基于SiO2波导的低耦合系数、窄线宽、高阶布拉格光栅特性研究

推导了布拉格光栅三维耦合系数公式,构建了一种新型的波导型布拉格光栅三维数值模型,并基于此设计制备出一种基于SiO₂平面波导结构的低耦合系数、窄线宽、高阶布拉格光栅。从理论设计和试验验证两方面系统分析了布拉格光栅刻蚀深度及占空比对光栅耦合系数和线宽的影响,并最终设计制备出了中心波长为1 554.053 nm,反射率为-8.5 dB,峰值半高宽为89 pm的SiO₂波导结构布拉格光栅器件。本文设计制备的低耦合系数高阶布拉格光栅器件工艺简单,成本低,在滤波器、传感器及外腔窄线宽激光器领域中有广阔的应用前景。     

高折射率厚平面光波导与光纤的水平耦合技术研究

光纤与平面光波导高效耦合是光波导器件互联设计中的重要环节,常用的倒锥波导已经解决了光纤与波导芯片之间的模式不匹配问题。然而,高折射率差波导与光纤耦合时通常需要较小的尖端尺寸(<180 nm),加工复杂且波导易坍塌。设计了一种宽波段(可见光和近红外波段)光纤-波导水平耦合器,通过引入聚合物SU-8锥形结构,提高了三端口分支波导的线宽,实现了850 nm波段超过300 nm的1 dB有效带宽。     

聚合物定向耦合电光开关的模拟和优化

阐述了定向耦合电光开关的基本结构及工作原理,利用耦合模理论和电光调制理论,在1 550 nm波长下,对器件的结构参量进行了优化,并对其传输光谱、开关电压、插入损耗、串扰等特性进行了分析.模拟过程中,考虑了因金属电极和聚合物材料引起的模式损耗.器件的结构参量优化值为：波导芯截面尺寸为1.7×1.7 μm2,波导芯与电极间的限制层厚度为1.5 μm、电极厚度为0.15 μm,波导间的耦合间距为2.0 μm,相应的耦合长度为2 926 μm.模拟结果表明,本文所设计的器件在开关转换电压0和17.4 V下,在1 534到1 565 nm的波长范围内,器件的插入损耗小于0.16 dB,串扰小于－20 dB,耦合区在2 734~3 120 μm范围内,器件的插入损耗小于0.22 dB,串扰小于－20 dB.     

集成光学声光可调谐光谱仪的特性分析

提出了一种以集成光学声光可调谐滤波器作为分光元件的新型光谱仪 ,并详细介绍了这种光谱仪的具体特性。通过对这种光谱仪的特征方程、点扩展函数以及色散本领的详细分析 ,指出该光谱仪的分辨本领与器件的声光作用长度成正比 ,也与它的级联级数的平方根成正比。因此增加器件的声光作用长度比增加它的级联级数能更有效地提高光谱分辨率。另外还指出 ,准共线声光耦合是抑制侧瓣、提高分辨本领的有效途径。测试表明 ,当声光相互作用长度L =2 5mm ,声波导和光波导的夹角θ=0 .4 2°时 ,在中心频率 174MHz附近可获得带宽 1.4 4nm ,一级侧瓣 - 13.2dB ,模式转换效率大于 99%的结果。     

低损耗有机无机混合溶胶凝胶波导的实验研究

利用有机无机混合的溶胶凝胶方法在硅基底上制备波导薄膜.采用正硅酸四乙酯和苯基三乙氧基硅烷作为反应先驱物,利用旋涂的方法成膜,对其折射率,传输损耗以及条形波导的光刻、刻蚀特性进行了研究.测量了波导薄膜折射率随成分变化的关系.实验表明,该方法工艺简单,可以获得具有较低损耗的波导薄膜.测试得到632.8 nm波段的损耗系数为0.23 dB/cm.采用ICP刻蚀工艺获得了较为平整的条形波导.     

偏振无关的双折射多波长滤波器的Z域设计

基于双折射铌酸锂晶体的电光效应,设计了一种偏振无关的二端口波导型多波长可调谐滤波器.在非对称干涉仪的上下分支波导上,耦合电极与相移电极周期性交叉级联实现模式的偏振转换.利用琼斯矩阵的Z域分析,求解驱动电压模拟实现多个波长的同时选择.仿真实现了自由光谱范围内分布任意的窄带多波长输出.波长中心处传输率为100%;旁瓣大小受到所选波长个数的影响,三个波长同时滤波的旁瓣可达12 dB.同时得到了梳状滤波输出谱,其通带顶部平坦,旁瓣可达15 dB以上.     

一种基于金刚石多层波导结构微环谐振器的仿真分析

提出了一种以金刚石新型材料为芯层的单微环谐振器模型.谐振器的纵切面采用五层脊形波导结构,中间一层设定为金刚石,上下两侧分别是SiO_2和As_2S_3,即As_2S_3-SiO_2-金刚石-SiO_2-As_2S_3.设置操作波长为1550 nm,依据耦合膜理论和微环谐振理论,利用Comsol软件仿真模拟了单直波导纵切面、直波导和环形波导耦合区的纵切面以及微环在谐振波长为1543 nm时的场强分布,及直波导和环形波导耦合区间距改变时微环的场强分布和传输特性.在此基础上,依据传输矩阵法讨论了微环的品质因数、耦合系数变化对输出光谱的影响,并对微环损耗进行了讨论.结果表明:以金刚石为芯层的微环谐振器具有良好的光学特性,本结构在谐振波长为1543 nm时谐振峰值达到了-12 dB以上,品质因数达到了1.54×10~5,在耦合系数为0.01时,自由光谱范围约为40 nm.     

新型杂萘联苯型聚芳醚砜硐聚合物光子材料成膜和光学特性

对新型聚合物光子材料杂萘联苯型聚芳醚砜硐(PPESK)波导薄膜的成膜工艺进行了系统的研究。分析了溶剂吸水性对成膜质量的影响,并通过氮气保护的方法获得了具有良好均一性的波导薄膜,其厚度一致性可优于1%,折射率一致性优于0.03%。采用棱镜耦合技术测量分析了PPESK波导薄膜的折射率、双折射、热光系数等光学特性,测量得到该材料在1310 nm波长处的损耗小于0.24 dB/cm,在1550 nm波长处的损耗小于0.52 dB/cm,表明该材料是一类性能良好的聚合物光子材料。     

两级串联声光可调谐滤波器旁瓣抑制的研究

阐述了偏振依赖的共线型和偏振无关的准共线型声光可调谐滤波器的滤波原理,进而导出了两级滤波的转换特性表达式;通过理论计算说明了两级声光可调谐滤波器能够有效地抑制旁瓣;最后,将两个单级的声光可调谐滤波器级联成两级滤波器,进行了旁瓣抑制的实验.实验结果表明,旁瓣被抑制到-19 dB,并且3 dB带宽也得到一定程度的压窄. 关键词： 集成光学 声光可调谐滤波器 旁瓣抑制     

All-fiber narrowband polarization controller based on coherent acousto-optic mode coupling in single-mode fiber

An all-fiber, narrowband, tunable polarization controller is proposed and demonstrated. The device is based on coherent acousto-optic mode coupling induced by two orthogonal acoustic waves on a dispersion-compensating fiber. The cooperative coupling between the two polarizations of the core mode and the TE01 cladding mode through the two gratings permits indirect coupling between the two polarizations of the core mode with nearly 100% efficiency, which makes the polarization-controlling function possible. Experimental results verify the operation of the polarization controller with an insertion loss of <1 dB.     

Compact acousto-optic filter with beam expanders constituted by photonic crystal rows of airholes

A compact acousto-optic (AO) filter with multireflector (MR) beam expanders constituted by 32 photonic crystal rows of airholes in LiNbO(3) waveguide has been proposed and numerically studied by the two-dimensional finite-difference-time-domain method. The diameter and position of every row of holes are gradually varied along MR beam expanders in order to provide high efficiency and good sidelobe suppression. Device sizes are 70 μm × 150 μm, with an FWHM bandwidth of 4.4 nm, a tuning range of 110 nm, internal loss of -3 dB, and sidelobes of -20 dB, thus providing a unique value of 0.6 μm(2) for the product FWHM bandwidth by an AO length. It is intended for use in fiber optics telecommunications and sensing.     

Coherent acousto-optic mode coupling in dispersion-compensating fiber by two acoustic gratings with orthogonal vibration directions

The acousto-optic mode coupling from core to LP11(cl) mode of a dispersion-compensating fiber excited by two acoustic waves with orthogonal perturbations is studied by use of a novel composite piezoelectric transducer. Highly polarization-dependent mode-selective spectra are observed that are due to coherent acousto-optic coupling between the core and various constituent cladding modes. Potential applications for implementing an all-fiber wavelength-tunable polarization analyzer are also discussed.     

Apodization of elliptical-core two-mode fiber acousto-optic filter based on acoustic polarization control

We propose and demonstrate a novel apodization technique for an elliptical-core two-mode fiber acousto-optic filter by twisting the fiber and adjusting the acoustic polarization. The sidelobe suppression in the filter spectrum was improved from -9.7 to -15.5 dB. A theoretical analysis that includes acoustic birefringence explains the experimental results with good agreement.     

All-fiber acousto-optic tunable notch filter with a fiber winding driven by a cuneal acoustic transducer

We report a type of all-fiber acousto-optic tunable notch filter consisting of a cuneal acoustic transducer and a fiber winding of four unjacketed single-mode fibers. With -32 dB peak rejection efficiency and 178 nm tunable range of the central wavelength, all of the tunable characteristics of the all-fiber acousto-optic tunable filter are kept. In addition, the structure is versatile and convenient for use in building other complicated filters. As an example, a coarse comblike filter has been built by adjusting the axial strains of the unjacketed fibers.     

Two-dimensional multi-channel acousto-optic diffraction

In this paper, we have investigated the interaction between acoustic waves generated by an incident light beam propagating through two-dimensional transducers. A set of coupled mode equations for two-dimensional multi-channel acousto-optic inter-modulation are derived, and the solutions are obtained. A new type of two-dimensional multi-channel Bragg acousto-optic modulator is designed by analyzing two-dimensional multi-channel acousto-optic inter-modulation based on the coupled mode theory, and its performance has also been experimentally characterized. The experimental results are in accordance with our theoretical analysis.     

Nonresonant cascaded acousto-optic mode coupling

Nonresonant cascaded acousto-optic mode coupling under an overall phase-matching condition is presented, where phase matching is not satisfied for each of the coupling stages but the sum of the two acoustic momenta matches the optical phase detuning between the source mode and the destination mode. As a special nonresonant cascaded case, conversion from LP(01) to LP(21) and LP(02) driven by a single acoustic frequency is predicted theoretically and demonstrated experimentally.     

The Experimental Study on Wide-band Tunable All-fiber Acousto-optic Filter Based on Null Coupler

The fiber acousto-optic filter is fabricated successfully for the first time in China. The mode conversion is realized by the acoustic-wave induced perturbation. Excess loss of 0.1 dB and continuous tuning range between 1470 nm and 1580 nm are obtained. The polarization dependence of the filter is studied experimentally.