一种基于导模共振的电光调制器研究

实验研究了基于导模共振的反射型电光调制器采用的棱镜耦合方式,在棱镜上面镀有4层膜,依次为银膜下电极-极化聚合物-缓冲层-金膜上电极。对这种衰减全反射（ATR）型的聚合物波导电光调制器进行了视频调制实验,采用静态偏置电压稳定模式同步角方法,结合对入射激光束进行监测,解决了视频调制中激光器噪声对模拟信号调制影响的问题,提高了工作稳定性。实验结果表明：该电光调制器具有良好的线性和较高的灵敏度。     

热交联型聚氨酯集成双通道电光调制器的制备及其性质的研究

研究了交联型聚氨酯材料集成衰减全反射型双通道聚合物波导电光调制器的制备和性能。这种电光调制器的制备技术非常简单,只要用两个分立的下电极代替单通道调制器中的下电极即可。通过测量器件的调制特性,在832 nm波长下,获得了最大电光系数为24.2 Pm/V,调制带宽约为500 MHz、插入损耗低于1.5 dB。由于器件上下电极的垂直距离为微米级、而通道之间的水平距离为毫米量级的设计,使各通道之间的场不会引起相互交迭,因而未测到各通道间的串扰。另外,热交联型聚合物材料的采用提高了整个器件的热稳定性,在100℃经过800 h后,电光系数仍然保持初值的88%。     

利用超高阶导模测量PMN-PT透明陶瓷二次电光系数

以亚毫米尺度的铌镁酸铅-钛酸铅(PMN-PT)透明陶瓷片为导波层制备了对称金属包覆波导,并利用自由空间耦合技术激发了波导中的超高阶导模.根据衰减全反射(ATR)峰的移动,得到了在波导两侧所施加电压与光强反射率的关系,从而计算了PMN-PT透明陶瓷片的二次电光系数.     

介质光栅导模共振耦合波分析

导模共振是由于光栅介质内高级次子波耦合进光栅所支持的泄漏模中,导致传播波能量重新分布的结果.采用严格的耦合波方法,通过分析波导的导波模式,正确估计出弱调制介质光栅导模共振的位置.并对导模共振与光栅厚度、基底厚度以及入射角的关系作了讨论.通过采用抗反射设计,获得了具有对称、低旁带特点的窄带共振峰 关键词： 导模共振 耦合波     

瑞利布里渊光时域分析系统中电光调制器的理论模型与实验研究

瑞利布里渊光时域分析系统能够以非破坏性方式实现单光源、单端工作,利用强度型电光调制器同时调制脉冲基底和脉冲信号是获得该系统所需连续光和脉冲光的关键技术.本文理论分析、仿真和实验研究了一种将脉冲信号输入到电光调制器偏置端、微波信号输入到电光调制器射频端同时调制脉冲基底和脉冲信号的新调制方法,探讨了电光调制器用于瑞利布里渊光时域分析系统时的最佳工作点问题.结果表明,当调制脉冲基底和脉冲时分别将电光调制器偏置在传输曲线的谷点和峰点,并根据实际系统的组成和性能指标要求选择合适的微波调制信号幅度,可获得满足瑞利布里渊光时域分析系统要求的连续光和脉冲光.本文的研究结果为瑞利布里渊光时域分析系统的最佳化设计提供了理论依据.     

瑞利布里渊光时域分析系统中电光调制器的理论模型与实验研究

瑞利布里渊光时域分析系统能够以非破坏性方式实现单光源、单端工作,利用强度型电光调制器同时调制脉冲基底和脉冲信号是获得该系统所需连续光和脉冲光的关键技术.本文理论分析、仿真和实验研究了一种将脉冲信号输入到电光调制器偏置端、微波信号输入到电光调制器射频端同时调制脉冲基底和脉冲信号的新调制方法,探讨了电光调制器用于瑞利布里渊光时域分析系统时的最佳工作点问题.结果表明,当调制脉冲基底和脉冲时分别将电光调制器偏置在传输曲线的谷点和峰点,并根据实际系统的组成和性能指标要求选择合适的微波调制信号幅度,可获得满足瑞利布里渊光时域分析系统要求的连续光和脉冲光.本文的研究结果为瑞利布里渊光时域分析系统的最佳化设计提供了理论依据.     

高效集成电光调制器和开关的电极与光波导的优化设计

集成电光调制与开关的效率取决于光波导中电光重叠因子Γ的大小，直接影响此因子的有电极宽度、电极间距、光模场尺寸、以及电极与光波导的相对位置等参量。本文利用集成电光调制器电极电场的分布规律，研究了各种结构中影响电光重叠因子的诸参量之间的关系；根据实际工艺条件，应用系统优化方法尽可能对各种参量进行优化计算，得到了实现高效调制和开关的全部参量的优化设计结果。     

波状PIN电光调制结构

PIN是电光调制器中常见的一种调制结构,该结构工作时产生的热光效应直接影响着电光调制器的性能。为了缓解这种热光效应对调制器的影响,从PIN调制原理出发,在绝缘体上硅薄膜(SOI)材料的基础上提出了一种波状PIN调制结构,并将该结构与普通PIN调制结构进行对比,定量分析了波状PIN结构对温度、折射率以及调制区载流子浓度的影响,通过仿真得出2V调制电压下,波状PIN结构的温度降低了11.6%,抑制热光效应使得折射率漂移减小了28%,调制区注入载流子浓度提高了26.7%。通过实验,分别制作了波状PIN结构和普通PIN结构的微环电光调制器,经过测试发现波状PIN结构具有更大的谐振峰蓝移值,该结构有效抑制了热光效应的影响,证明了该新型结构的优越性及理论分析的正确性。     

对称金属包覆波导受温度影响的特性分析

基于对称金属包覆波导,研究了温度对金属层介电常量及导波层折射率的影响.通过改变金属介电常量和导波层折射率,共振角和衰减全反射吸收峰受到影响.理论和仿真表明:在入射光波长为760nm,覆盖层银膜厚度为35nm,衬底银膜厚度为300nm,导波层为纯水的条件下,温度由10℃升高到70℃时,衰减全反射吸收峰反射率随温度的升高而降低,吸收率提高;共振角随温度的升高,先增加后减小.当金属介电常量对整体的影响大于纯水时,共振角增加,反之,共振角减小.因此,对称金属包覆波导受温度的影响是不可忽略的.     

包含左手材料的四层平板波导中的光导模

研究一个芯子层是左手材料,其他三层由传统材料构成的四层平板光波导系统,利用图解法对各种TE偏振的导波模式的解进行详细分析.研究表明,四层左手材料光波导既能支持振荡导模,也能支持表面导模,与三层左手材料光波导相比较,此四层波导的导波模式呈现一些新的特性.对于中间传统材料层存在振荡场的情形:芯子层支持振荡导模的光波导中存在基模,并且高阶振荡导模出现模式缺失的性质;芯子层支持表面导模的光波导可以支持基模和多个高阶模式,并且存在模式兼并的性质.对于中间传统材料层存在衰减场的情形,此四层波导结构可等效为三层左手材料光波导.这些新的光波导传输性质对各种光波导器件的制作有潜在的应用价值.     

Dynamic trapping of light in modulated waveguide lattices

A discrete analogue of the dynamic (Kapitza) trapping effect, known for classical and quantum particles in rapidly oscillating potentials, is proposed for light waves in modulated graded-index waveguide lattices. In particular, it is shown that, while a graded-index potential in a nonmodulated waveguide lattice can confine light at either normal or Bragg angle incidence, periodic modulation of the potential in the longitudinal direction enables one to trap optical beams at both normal and Bragg incidence angles.     

Electrically controlled waveguide mode in LC layer for fiber optic applications

A new electrically controlled waveguide mode for optical beams propagating in the plane of a liquid crystal (LC) layer is described. The mode is based on the total internal reflection of light beams from two parallel boundaries, which separates the regions of a liquid crystal cell with different director orientations and refractive indices. In experiments electric field was applied to the initially planar layer to produce the channel with a homeotropic orientation surrounded by the planar regions. It results in focusing and waveguide propagation of a light beam emitted by an optical fiber inserted in a liquid crystal cell. Scattering of light by thermal LC director fluctuations is used to visualize light beams propagation. The obtained waveguide mode can be used for an elaboration of electrically controlled LC switches with low operating voltages. The prototype of such device made with usage of a photolithography and a photo alignment technique is described. The possible ways of optimization of LC-switch are considered.     

金属异质波导阵列中的表面等离激元传播特性

提出了一种新的一维金属异质波导阵列的设计方案,即波导芯区周期调制的金属波导阵列.数值模拟的结果表明,金属波导芯区的周期调制引起波导中传播的表面等离激元有效折射率的周期调制,从而可在特定的波段打开一个表面等离激元带隙(如1550nm附近).通过引入合适的缺陷波导单元,可获得特定波长的高品质因子(Q=556)的表面电磁模共振.这一结果可用于设计亚波长的布拉格反射器、光发射器、滤波器等,有可能被用于未来的集成光路.     

4pi聚焦系统中振幅和相位调制的径向偏振涡旋光束聚焦特性的研究

基于Richards-Wolf矢量衍射积分公式, 研究了径向偏振涡旋光束在振幅和相位调制下的4pi聚焦特性.振幅调制是通过振幅滤波实现, 即改变入射光束起始积分值达到调节,相位调制是通过添加相位延迟角δ 的液晶相位延迟器来改变入射光束的偏振态.模拟结果显示,随着振幅的减小, 4pi聚焦系统焦点附近的光轴上呈现出多光球结构; 而相位调制对焦点附近的光强分布产生拉伸作用, 即调节入射光束的拓扑核m和相位延迟器的延迟角δ,可以得到特殊的光强分布. 随着相位δ增大, m=0产生的多光球结构慢慢向光链结构转变,最终变成暗通道;而m=1产生的光链结构慢慢变成光球结构; m=2产生的暗通道变成光球和光链叠加的结构, 这种特殊聚焦光束在光学微操纵领域具有潜在的应用价值. 关键词： 物理光学 偏振 光链 4pi聚焦系统     

Harmonic and intermodulation performance of active integrated-optic waveguides

An empirical formula is developed for the static input/output optical characteristic of the active integrated-optic waveguide. Using this formula, closed-form analytical expressions, in terms of the ordinary Bessel functions, are obtained for the output optical components resulting from a modulated multisinusoidal optical input. Using these expressions the effect of the wavelength of the light input, the guide width, the modulation depth and the optical power for transperancy on the harmonic and intermodulation performance of the active integrated-optic waveguide can be studied.     

亚波长介质光栅导模共振研究

从平板波导的本征值方程出发,导出弱调制介质光栅共振位置的表达式,其预测结果与利用严格的耦合波理论所得值一致.对正入射时导模共振产生双反射峰现象进行解释,并就导模共振对入射角和光栅周期敏感性的成因进行了探讨.从薄膜的特征矩阵方程出发,在理论上分析了利用导模共振获得性能良好的反射滤光片的途径.     

Generation of millimeter wave Gaussian beams and their propagation in a dielectric waveguide

Linearly polarized fundamental mode Gaussian beams were generated and coupled to a hollow circular oversized dielectric waveguide by placing the waist of the beam at the guide entrance. The transmission properties of the waveguide were characterized as a function of frequency for a variety of coupling conditions. These conditions included changes in the input beam waist radius, angle of incidence, and displacement perpendicular and parallel to the guide axis. It has been found that: 1.) power transmission is maximized when the waist of the input beam is centered at the guide input, injected normally, and has a radius of 0.43 times the waveguide radius, 2.) power transmission decreases rapidly with increasing angle of incidence and the rate of that loss increases with frequency, 3.) the waveguide preserves the linear polarization of the input beam, 4.) power transmission in the fundamental waveguide mode is not greatly affected by moderate displacements in the input beam position, and 5.) upon exit from the waveguide the launched EH₁₁ mode propagates as a fundamental mode Gaussian beam in the quasi-far field. The results compare favorably to the transmission theory of Belland and Crenn and approximately to the near and far field mode pattern theory of Degnan.     

Multi-channel light modulation based on the attenuation total reflection

Multi-channel light modulation, which is based on the attenuated total reflection (ATR) configuration, is proposed in this paper. The device consists of a prism and a polymer optical waveguide. Guided modes which give rise to the resonance dips in the ATR spectrum are employed to act as the modulation channels. Double channel's modulation with the same modulation signal has been demonstrated in the proposed device.     

Grating coupled interferometry for optical sensing

An interferometric sensor based on gratings on a planar waveguide is introduced. The device combines the advantages of known interference-based waveguide sensors with the simplicity of grating couplers. In the presented configuration, two parallel and coherent light beams, laterally separated in the direction of mode propagation, are coupled into a planar waveguide through a grating. One of the coupled beams is phase modulated using a periodically relaxing liquid crystal modulator, resulting in a time varying intensity signal at the end face of the waveguide. Refractive index changes within the waveguide section between the two coupling regions are monitored by observing characteristic changes in the intensity signal.