Mode theory of three-layer cylindrical waveguides and its application to aurum(Au)/polystyrene(PS)-coated terahertz hollow waveguides

In this paper, we present a generic mode theory for the three-layer cylindrical waveguides consisting of three arbitrary material mediums. Based on derived eigenvalue equations of the TE, TM, and hybrid modes, the mode conditions of metal/dielectric-coated terahertz hollow waveguides are extracted. In addition, we quantitatively describe both the effective refractive indexes and the loss characteristics of the aurum/polystyrene-coated terahertz hollow waveguides operating at the TE₀₁, TM₀₁, and HE₁₁ modes. It is indicated that the loss coefficient of the TE₀₁ mode can be much lower than that of the TM₀₁, and HE₁₁ modes, and, especially, can tend to that of the terahertz wave in air. So the TE₀₁ mode is very significant for the hollow waveguides in term of low loss propagating of the terahertz wave. We expect these results to enable a variety of new long-distance THz applications in sensing, detecting and communicating.     

F8BT：P3HT共混薄膜的放大自发辐射

研究了聚合物poly（9,9-dioctylfluorene-co-benzothiadiazole）（F8BT）和poly （3-hexylthiophene）（P3HT）共混薄膜的放大自发辐射（ASE）现象,对影响其阈值的两个因素--增益和损耗进行了详细的研究。结果显示,共混聚合物的发光效率随着P3HT所占比例的增加有所降低。当P3HT比例低于20%时,发光效率降低不多,而其损耗则随着P3HT的增加显著减小。F8BT和P3HT混合后,光损耗系数从7.8 cm^-1下降到4 cm^-1左右。这表明F8BT：P3HT共混聚合物光波导的ASE阈值降低主要是由于其损耗的降低而导致的。ASE阈值的降低预示该材料体系容易实现电泵浦激光。     

气相沉积法制备聚酰亚胺微球的均匀性及性能

为满足惯性约束聚变(ICF)对聚酰亚胺(PI)靶丸的要求,研究了气相沉积过程单体加热温度对PI薄膜厚度的影响并测试其均匀性,测试了脉冲敲击模式下复合微球的表面质量。研究了薄膜热环化过程中的结构变化,并对所得PI薄膜进行了热稳定性分析。研究结果表明:脉冲敲击下制备所得复合微球表面粗糙度均方根值波动在29~45nm之间,在相同时间内其薄膜厚度随单体加热温度的增加而增加,通过调节不同单体加热温度,可将薄膜厚度控制在一定范围;薄膜厚度测试发现其较为均匀,横向和纵向各点厚度相差不足1μm;热环化后聚酰胺酸转化为PI,CONH与COOH结合形成C-N键;热重分析数据显示PI薄膜热稳定性较好,600℃左右才开始大量分解。     

Contra-directional coupling between two-dimensional photonic crystal waveguides

The contra-directional coupling between two photonic crystal (PC) waveguides is studied, using the finite-difference time-domain (FDTD) method. A design of contra-directional coupler is presented and its transmission properties are investigated. The device can be used as an add/drop filter. It is also shown that the coupled mode theory is suitable to study the photonic crystal waveguide coupler.     

Few-photon routing via chiral light-matter couplings

A quantum router is one of the essential elements in the quantum network. Conventional routers only direct a single photon from one quantum channel into another. Here, we propose a few-photon router. The active element of the router is a single qubit chirally coupled to two independent waveguides simultaneously, where each waveguide mode provides a quantum channel. By introducing the operators of the scatter-free space and the controllable space, the output state of the one-photon and two-photon scattering are derived analytically. It is found that the qubit can direct one and two photons from one port of the incident waveguide to an arbitrarily selected port of the other waveguide with unity, respectively. However, two photons cannot be simultaneously routed to the same port due to the anti-bunch effect.     

制备多模聚硅氧烷光波导关键技术的改进

本文利用浇铸法,使用M&N胶和OE6450两种聚硅氧烷制备光波导.通过改进制备光波导的多个关键技术, 解决了波导制备过程中的气泡问题、脱模问题、芯层不固化问题、芯层和覆盖层产生化学反应等难题,提出了 比较完备和科学的聚硅氧烷波导制备工艺流程,从而使得波导的制备成品率从原来低于40%提高到高于80%, 波导的最大长度从原来的21 cm增加到22.5 cm,波导的损耗(截断法测量结果)从最初的0.3dB/cm(850 nm)降低到了 0.21dB/cm(850nm).本文在波导制备技术方面具有重要的实际意义和价值.     

低损耗低非线性高负色散光子晶体光纤的优化设计

设计了一种同轴双芯六角点阵光子晶体光纤, 该光纤中心缺失一根空气柱形成内纤芯, 通过减小第4环空气孔的直径形成外纤芯. 采用全矢量有限元法并结合各向异性完美匹配层边界条件, 对其色散、非线性、约束损耗和模场等特性进行了数值模拟. 结果发现, 该光纤呈现高负色散可调效应和较强的模场约束能力, 约束损耗接近10^-2 dB· m^-1. 调整光纤结构参数(即空气孔间隔Λ, 小孔直径d₁和相对孔间隔比f), 可以控制其高负色散工作波长. 若调整光纤结构参数Λ=1.2 μ, f=0.917, d₁=0.515 μm时, 该光纤在低损耗通信窗口C波段呈现负色散和负色散斜率, 其色散斜率在-1----6 ps· km^-1nm^-2范围内波动, 在波长1.55 μm处负色散值为-3400 ps· km^-1nm^-1, 模场面积高达43 μm², 非线性系数仅有3.6 km^-1W^-1. 该光纤在C波段呈现的低损耗低非线性高负色散特性, 具有很好的色散补偿能力, 将在长距离大容量 高功率高速光通信系统中获得很好的应用.     

光子晶体表面光波导的特性研究

采用平面波展开法和时域有限差分法,研究了光子晶体表面光波导的色散及光传输特性。研究结果表明,表面模的出现及其色散特性与表面介质柱的半径相关,色散曲线的斜率保持单调变化,并在最低或最高频率附近展现低群速度频率区。由于光子带隙和全内反射的共同影响,光场将沿晶体表面高效率地传输。研究结果为探索在光子晶体外部控制光传输具有重要的理论意义。     

Patterned Deposition of Sol-Gel Thin Films Using an Airbrush

ABSTRACT

In this article, we present a method to pattern glass substrates with sol-gel derived thin films. This method is based on the aerosol deposition of sol-gel precursor solutions using an inexpensive, commercially available airbrush. The technique was demonstrated using Cy5-doped sol-gel thin films for the creation of wavelength conversion devices. The films deposited were mechanically and chemically rigid, and patterns could be achieved with a resolution limit of approximately 250 μm. Constructing channel waveguides was also attempted using both zirconium- and titanium-based sol-gel thin films. Deposited thin films of these materials showed graininess that limited the ability to couple light into the films and increased the observed scatter. However, light was successfully coupled into the titanium-based sol-gel film using small lens-like structures created on the glass surface.