Dispersion modified slot optical waveguides

Advent of slot waveguide structures had opened a new era where light can be confined in low index slot guarded by high index slabs. Already in use SOI slot waveguides (contrast ratio is 2.42) have two distinct properties over the conventional waveguides, i.e. high E-field amplitude, optical power, optical intensity in low index materials, and strong E-field confinement localized to nanometer-size low index regions. We hereby propose a low refractive index contrast ratio slot waveguide structure (ratio is 1.18) comprising of commercially available glass material. Novelty lies in showing high E-field amplitude, optical power, optical intensity, and strong E-field confinement in low index slot regions despite of lowest ever reported contrast ratio. A systematic numerical study on the higher order dispersion characteristics of the widely studied SOI-based slot structure and of our proposed low refractive index contrast slot structure is carried out. It has been demonstrated that low refractive index contrast ratio slot optical waveguide GVD properties are quite different than SOI slot optical waveguide. The less normal dispersion existing in this kind of waveguide could have an impact on their applications in various nonlinear or linear applications.     

平面环形谐振腔微光学陀螺结构设计与优化

提出具有高群有效折射率的双环级联作为核心元件的谐振式平面光波导陀螺结构, 基于光学Sagnac原理得到了双微环耦合谐振式光学陀螺理论灵敏度与群有效折射率的一般表达式和双环与单环陀螺系统的灵敏度关系, 并由耦合模理论方法得到了双环系统耦合器的两个透射系数对应的群有效折射率变化情况. 在环腔半径R₁=R₂=100 μm、环腔传输损耗系数t₁=t₂=0.95的情况下, 针对环与环之间耦合器和环与波导之间耦合器透射系数对群有效折射率的不同影响, 得到了最大群有效折射率的产生条件. 采用文中参数(R=100 μm, t=0.95)计算的单环谐振式陀螺灵敏度为(10⁴-10⁵)°/h, 而双环级联谐振系统理论灵敏度能够达到10 °/h. 该研究对微环耦合谐振腔在角速度检测上的应用有重要的意义.     

亮孤子在宇称时间对称波导中的传输和控制

基于光波在宇称-时间(PT)对称波导中传输的理论模型, 数值研究了亮孤子在呈高斯分布的PT对称克尔非线性平板波导中的传输和控制. PT对称波导, 要求波导的折射率分布呈偶对称, 而增益/损耗分布呈奇对称. 结果表明: 当波导的折射率分布强度为正时, PT对称波导的中心折射率最大, 即使没有自聚焦克尔非线性效应, PT对称波导也可以束缚光波, 形成波浪形光束且长距离传输; 当折射率分布强度为负时, PT对称波导的中心折射率最小, 光波的传输方向发生偏移. 而增益/损耗分布可控制光波的偏移方向: 增益/损耗分布强度为正, 光波向左偏移; 强度为负, 光波向右偏移; 强度为零时, 光波被分为两束. 且当折射率分布强度为负时, 可以很好地抑制相邻亮孤子间的相互作用. 该研究结果可为未来PT对称波导在全光控制方面的应用提供一定的理论依据.     

全电极脊形波导光传输特性

给出一种较为简便的全电极脊形波导的分析方法,即采用有效折射率方法把此金属包层脊形波导化成一个二维等效平板波导,然后利用微分法得到模的有效折射率满足的方程和吸收损耗系数的解析表达式.作为一个特例,用这种方法对SiO2全电极脊形波导光传输特性如光传播常数和损耗进行了计算, 并得到一些有益的结论.     

γ辐射对光纤波导电磁场分布的影响

开展了光纤波导中的电磁场传输理论分析,得到了光纤折射率变化对波导中电磁场分布的影响规律,建立了块状融石英材料及光纤光栅在60Co 辐射作用下折射率变化的测量系统,开展了折射率随辐射剂量变化及光纤模场测量实验。结果表明:光纤的折射率随辐射剂量的增加而增大,折射率的变化会引起波导中传输模式的场强分布变化,从而导致光纤的辐射感生波导损耗;在一定的辐射剂量范围（0～2000 Gy）内,光纤仍满足弱导边界条件,能够维持对传输模式的约束能力。     

Intersubband optical absorption coefficient changes and refractive index changes in a two-dimensional quantum pseudodot system

The optical absorption coefficient changes and refractive index changes associated with intersubband transitions in a two-dimensional quantum pseudodot system under the influence of a uniform magnetic field are theoretically investigated. In this regard, the electronic structure of the pseudodot system is studied using the one-band effective mass theory, and by means of the compact density matrix approach linear and nonlinear optical absorption coefficient and refractive index changes are calculated. The effects of an external magnetic field and the geometrical size of the pseudodot system on the optical absorption coefficient and refractive index changes are investigated. It is found that the absorption coefficient and refractive index changes are strongly affected not only by an external magnetic field but also by the geometrical size of the pseudodot system.     

Calculation of the absorption coefficients of optical materials by measuring the transmissivities and refractive indices

In this paper, a formula for accurate calculation of the absorption coefficient of optical material is deduced by the relationship of its transmissivity, refractive index and absorption coefficient. Because the values of transmissivity and refractive index of the optical material with a higher accuracy can be determined by the instruments or obtained directly from the references, the calculated results of the absorption coefficients with a higher accuracy is certified. The absorption coefficients of some optical materials are calculated with it, and the results are discussed.     

基于Optiwave的脊形SiGe OI光波导结构设计

利用有效折射率的数值解法,计算出了SiGe OI脊形光波导的有效折射率.通过对SiGe OI光波导结构参量的理论分析和计算,得到了SiGe OI脊形光波导传输单模光波时内外脊高H,h及脊宽W的尺寸.通过Optiwave软件对SiGe OI脊形光波导进行建模仿真,验证了理论分析和计算的正确性.     

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。     

基于SM-NCF反射光谱辨识的液体折射率监测方法

针对分子生物学与环境监测领域高灵敏度特异性检测需求,提出一种基于反射光谱特征辨识的单端反射式光纤折射率传感器模型,并给出了这种基于多模干涉原理的单模光纤-无芯光纤(Single mode fiber-No core fiber, SM-NCF)串接结构传感机理及其理论模型。无芯光纤实质上是一种结构特殊的多模光纤,在实际应用中无芯光纤结构本身作为纤芯,外界环境介质当作包层,构成光波导结构。这与普通多模光纤相比,不需要采用氢氟酸对多模光纤的包层进行化学腐蚀,不会降低光纤的机械性能,也不会破坏芯模传输条件,可以更好的实现对周围环境折射率的传感监测。当无芯光纤所处外界环境折射率发生改变时,其波导结构和包层有效折射率均会发生改变,从而引起传输光信号的纵向传播常数和模场分布也会随之发生改变,最终导致不同波长对应传输光功率的变化。上述效应反映在反射光谱上,即干涉波谷对应的谐振波长、波谷峰值强度以及半波宽度发生相应变化,通过辨识该反射光谱特征就可实现对外界环境折射率的测量。借助光束传播法(BPM),数值模拟得到无芯光纤长度分别为自映像距离和非自映像距离时的SM-NCF内部光场能量分布规律,并制作了无芯光纤长度分别为自映像距离和非自映像距离的SM-NCF光纤折射率传感探头,将作为传感区域的无芯光纤一端与标准单模光纤熔接,采用磁控溅射技术在无芯光纤另一端面镀上金膜,用以提升反射光谱强度。在此基础上,搭建了基于SM-NCF终端反射型的光纤折射率试验系统,并开展了相关实验研究。研究结果表明,当无芯光纤长度是15 mm(自映像距离)时,随着液体折射率从1.331 5依次增大至1.390 2,SM-NCF反射光谱逐渐向长波方向偏移,其反射峰谐振波长对应的折射率灵敏度约为197.57 nm·RIU-1,相关系数为0.93;反射峰值强度也呈现逐渐降低趋势,其折射率灵敏度约为-62.80 dB·RIU-1。当无芯光纤长度是20 mm(非自映像距离)时,随着液体折射率依次增大,SM-NCF反射光谱呈现明显双峰现象,且均逐渐向长波方向偏移,dip2谐振峰波长折射率灵敏度约为133 nm·RIU-1,相关系数为0.96;反射峰值强度也呈现逐渐降低趋势,其折射率灵敏度约为-31.66 dB·RIU-1。对比分析可知,不论是从反射峰谐振波长偏移的角度,还是从反射峰值强度的角度,自映像距离长度对应的 SM-NCF终端反射型光纤传感器均具有较高灵敏度。对于相同折射率液体环境,非自映像距离长度对应的SM-NCF反射光谱半波宽度与自映像距离长度相比,呈现显著变窄趋势。相对于SMS透射型传感结构,当传感区域长度相同时,SM-NCF反射型结构能够实现对光波信号的往返两次调节。这种终端反射型SM-NCF传感器改进了传统透射型折射率传感器不便与待测液体相接触的缺点,具有结构简单、易于制作、抗电磁干扰能力强以及便于远程遥测等优点,能够为后续生化与环保监测领域研究应用提供有益支持。     

从薄膜波导传播衰减的角度研究光学薄膜的损耗:(Ⅰ)理论分析

本文从理论上分析了光学薄膜中的三种基本缺陷:折射率消光系数、表面粗糙度以及折射率不均匀性对薄膜内导波传播衰减的影响.基于这些缺陷对光学薄膜内不同导模传播衰减作用的不同,提出了一种区分薄膜中的吸收与散射损耗的方法.     

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.     

Intersubband optical absorption coefficients and refractive index changes in a parabolic cylinder quantum dot

Optical absorption coefficients and refractive index changes associated with intersubband transition in a parabolic cylinder quantum dot are theoretically investigated. In this regard, the electronic structure of the dot is studied using the one band effective mass theory, and by means of the compact-density matrix approach the linear and nonlinear optical absorption coefficients and refractive index changes are calculated. The effects of the size of the dot, optical intensity and electromagnetic field polarization on the optical absorption coefficient and refractive index changes are investigated. It is found that absorption and refractive index changes are strongly affected not only by the size of the dot but also by optical intensity and the electromagnetic field polarization.     

Waveguide technique for measuring thin film parameters

A waveguide technique for measuring the absorption coefficient, refractive index, and thickness of thin films is suggested. It is based on taking the angular dependence of the light beam reflection coefficient in an optical scheme involving a prism coupler. Application of the technique to determining the parameters of thin-film waveguides, insulating coatings, and metal films is considered.     

电光聚合物波导中的锥形结构

提出并设计了一种基于电光聚合物的锥形波导,可用于单模光纤与电光聚合物波导器件之间的连接.锥形波导中采用了宽度锥形和折射率锥形结构.宽度锥形采用劈形形状,通过宽度和折射率的缓慢变化实现模场转换.劈形形状的宽度锥形具有较小的损耗且易于制作,折射率锥形可采用灰度掩膜光刻技术制作.研究了锥形波导的传输损耗与锥形波导的长度、波导宽度和厚度、材料吸收损耗等参数的关系及其优化,分析了锥形波导中的功率传输、模场分布与模式转换效率.结果显示锥形波导的传输损耗小于0.37 dB,光纤-波导-光纤的连接损耗优于1.62 dB,对插入损耗的改善达到8.78 dB,模场转换效率达到了83.7%.     

Factors affecting optical dispersion in borate glass systems

Series of ternary glass systems namely, Na₂O, B₂O₃, and RO (R=Ba or Mg) doped with TiO₂ are synthesized. The present glasses are dictated by requirement for a small refractive index and a small nonlinear coefficient needed for waveguide and laser fabrication requirements. The effect of MgO and BaO as alkaline earth metals on the optical properties of the glass systems is investigated. The dependence of the refractive index and extinction coefficient dispersion curves on composition is carried out over a wavelength range of 0.3-. Applying a genetic algorithm technique, the parameters of Sellmeier dispersion formula that fit index data to accuracy consistent well with the measurements are given. The zero material dispersion-wavelength (ZMDW) and group velocity are also determined using the refractive index data. The Fermi level is calculated exploiting the extinction coefficient dispersion curves. The absorption coefficient, both direct and indirect optical energy gaps, and Urbach energy are evaluated using the absorption edge calculations. The different factors that play a role for controlling the refractive indices such as coordination number, electronic polarizability, field strength of cations, bridging and nonbridging oxygen, and optical basicity are discussed in accordance with the obtained index data. IR spectroscopy is used as a structural probe of the nearest-neighbor environment in the glass network.     

Computational analysis of metamaterial–aluminum–silicon solar cell model

In this paper, the optical parameters of an improved waveguide structure for a more efficient silicon solar cell are studied. Despite its favorable electronic, physical, and chemical properties, silicon remains a poor absorber of light. The optical losses due to the reflection at the air/glass interface of the cell and the transmission at its back are other factors, which limit the cell conversion efficiency. Consequently, several mechanisms for light trapping capable to increase the collection of the incident photons as electrical current and to decrease the transmission loss, have been developed. In this context, we propose a multilayer waveguide structure in which the sunlight is guided by a metamaterial layer and the transmission loss is eliminated by an aluminum back reflector. The reflection and transmission coefficients are derived by using the Generalized Transfer Matrix Method. The application of the law of conservation of energy allowed the determination of the absorption coefficient. These optical parameters are examined for several angles of incidence for s-polarized light, p-polarized light and unpolarized light. Simulation results show a significant reduction of reflection and a complete suppression of transmission.     

Characterization of evaporated selenide semiconductor alloy on p-type substrates

The properties of chalcogenides that are most important for applications as infrared transmitting materials are reported and their mutual relationships are given. Si₅Se₈₀In₁₅ films were produced by means of thermal evaporation. The refractive index and the optical energy gap were determined by transmission measurements. Parameters considered in this study are density, molar volume, transition temperatures, electrical properties, infrared transmission, extinction coefficient and refractive index. This composition has no extrinsic and intrinsic absorption between 14 and 20 μm and the value of absorption coefficient is estimated lower than 10⁻³ cm⁻¹ at 10.6 μm. This glass is also suitable for infrared optical elements. A p-n junction is observed due to evaporated thin film of alloy on p-type Ge substrate.     

基于离子交换条波导的生物溶液浓度传感研究

提出并实施了一种实验推定离子交换单模条波导折射率分布的新方法,给出扩散系数可用常量等效的离子交换条件,导出了条波导离子交换制备过程的两维扩散方程的一般解,拟合推定了离子交换条波导的折射率分布.多波长测试的折射率色散通过引入玻璃色散关系解决,样品测试中表征导模吸收损耗的传播常量虚部由KK变换确定.在此基础上,试制了光纤-条波导-光纤一体化传感器结构,验证实测了多种不同浓度的葡萄糖溶液,最低检测限为0.1 μM,实现了低浓度微量测试,验证了条波导传感机制的有效性.