亚波长尺度下混合等离子泄漏模式激光

由于光存在衍射极限,因此传统方法不能实现亚波长尺度下的激光激射。为了打破这一衍射极限,本文设计了金属-介电层-半导体堆叠结构来实现深亚波长尺度下的激光激射,并讨论了相关结构对模式传播的影响。结构设计上,采用低介电常数金属银作为衬底、10 nm厚的LiF作为介电层、具有六边形截面的半导体纳米线ZnO作为高介电常数层,采用有限差分本征模和时域有限差分方法对所设计的结构进行光学仿真模拟。首先,通过改变ZnO纳米线的直径,使用有限本征模方法分析介电层中的光学模式,得到4种模式分布。然后,通过这4种光学模式在不同纳米线直径下的有效折射率和损耗计算了对应的波导传输距离以及激射阈值增益。最后,采用三维时域有限差分方法仿真分析纳米线稳态激光发射过程中各模式的电场分布。结果表明:在纳米线和金属衬底之间的介电层上存在混合等离子体模式和混合电模式,对于直径低于75 nm的ZnO纳米线,没有有效的物理光学模式,即混合等离子体模式和混合电模式都被切断,当ZnO纳米线的直径大于75 nm时,混合等离子体模式可以有效存在,而混合电模式在ZnO纳米线的直径达到120 nm之后才出现。虽然混合等离子体模式可以更好地限制在介电层中,但是它们的模式损耗太大,传播距离相对较小。此外,与混合等离子体模式相比,混合电模式的传播距离更长。在给定微米线的直径(D=240μm)下,混合电模式传播距离超过50μm。综上可知,在深亚波长尺度下利用混合泄漏模式可以打破光学衍射极限并实现激光激射。     

Selective area rare-earth doping of planar glass samples for monolithic integration of optically passive and active waveguides

Successful demonstration of selective area doping of planar glass samples for monolithic integration of optically passive and active devices on a single chip is presented. Salt solution of erbium was delivered onto pre-sintered germano-silicate samples via a syringe. The samples were then consolidated to form dense glass layers containing regions doped with rare earth. Erbium tri-chloride solution, 0.1 M, was used during the solution doping phase, with the resulting erbium atomic percentage ranging from more than 0.1-0.4%, increasing linearly with the number of drips applied.     

Analysis for Transmission Characteristics of Closed Trapezoidal-Groove Waveguide with Boundary Element Method

In this paper, the cut-off and dispersion characteristics of a new kind of closed trapezoidal-groove waveguide that has more advantages than open groove waveguides are analyzed with the help of the boundary element method, the relationship between cut-off wavelengths and variations of guide's relative sizes is discussed in detail. The calculated results are in good agreement with those in the relevant reference. So, the obtained conclusions are very important in theoretical studies and actual applications of closed trapezoidal-groove waveguides for millimeter and submillimeter waves.     

Elastic Organic Crystals Based on Barbituric Derivative: Multi-faceted Bending and Flexible Optical Waveguide

Elastic organic single crystals with light-emitting and multi-faceted bending properties are extremely rare. They have potential application in optical materials and have attracted the extensive attention of researchers. In this paper, we reported a structurally simple barbituric derivative DBDT , which was easily crystallized and gained long needle-like crystals (centimeter-scale) in DCM/CH₃OH (v/v=2/8). Upon applying or removing the mechanical force, both the (100) and (040) faces of the needle-like crystal showed reversible bending behaviour, showing the nature of multi-faceted bending. The average hardness (H) and elastic modulus (E) were 0.28±0.01 GPa and 4.56±0.03 GPa for the (040) plane, respectively. Through the analysis of the single crystal data, it could be seen that the van der waals (C−H⋅⋅⋅π and C−H⋅⋅⋅C), H-bond (C−H⋅⋅⋅O) and π⋅⋅⋅π interactions between molecules were responsible for the generation of the crystal elasticity. Interestingly, elastic crystals exhibited optical waveguide characteristics in straight or bent state. The optical loss coefficients measured at 627 nm were 0.7 dBmm⁻¹ (straight state) and 0.9 dBmm⁻¹ (bent state), while the optical loss coefficient (α) were 1.5 dBmm⁻¹ (straight state) and 1.8 dBmm⁻¹ (bent state) at 567 nm. Notably, the elastic organic molecular crystal based on barbituric derivative could be used as the candidate for flexible optical devices.     

半波长超导共面波导谐振腔传输及温度特性研究

超导共面波导谐振腔主要包括四分之一波长型和半波长型.本文对半波长超导共面波导谐振腔使用并联RLC电路进行等效分析,使用sonnet软件进行仿真其传输特性,通过电子束蒸发和激光直写等工艺制备出样品,在低温超导状态下使用矢量网络分析仪对其传输特性进行测量,以及通过持续降温方式研究其传输特性受温度的影响.实验表明:测得的谐振频率和外部品质因数与设计值吻合;谐振频率受动态电感的影响随温度降低而升高;外部品质因数随温度降低而保持基本不变;内部品质因先受导体损耗的影响随温度降低而急剧升高,当温度降低至一定温度后内部品质因数受介电损耗的影响随温度降低而保持基本不变;总品质因数在温度较高时主要来自于导体损耗,在温度较低时主要来自于介电损耗和外部品质因数,随温度的变化趋势和内部品质因数一致.     

1,3-二苯基-2-吡唑啉纳米带的制备及其光波导性质

以1,3-二苯基-2-吡唑啉(DP)为目标化合物, 利用再沉淀方法, 以混合溶剂作为不良溶剂, 制备了形貌均一、宽度约2 μm、厚度200 nm和长度数十微米的一维纳米带状结构. 选区电子衍射结果证实, DP分子在纳米带中因为强的分子间π-π相互作用而沿着晶体[100]方向优势生长. 稳态光谱结果表明, DP纳米带具有不同于分子和体相材料的介观特性. 由于J-聚体在DP纳米带中优势形成, 其480 nm的发射峰与分子和体相材料相比分别红移了30和20 nm. 利用扫描近场光学显微镜进一步发现, 一维DP纳米带类似于天然的亚波长尺度谐振腔, 紫外激发DP分子发射的荧光被限域在DP纳米带中, 沿一维方向传导并在两端耦合输出.     

Photonic band structures of quadrangular multiconnected networks

By means of the network equation and generalized dimensionless Floquet-Bloch theorem,this paper investigates the properties of the band number and width for quadrangular multiconnected networks (QMNs) with a different number of connected waveguide segments (NCWSs) and various matching ratio of waveguide length (MRWL).It is found that all photonic bands are wide bands when the MRWL is integer.If the integer attribute of MRWL is broken,narrow bands will be created from the wide band near the centre of band structure.For two-segment-connected networks and three-segment-connected networks,it obtains a series of formulae of the band number and width.On the other hand,it proposes a so-called concept of two-segment-connected quantum subsystem and uses it to discuss the complexity of the band structures of QMNs.Based on these formulae,one can dominate the number,width and position of photonic bands within designed frequencies by adjusting the NCWS and MRWL.There would be potential applications for designing optical switches,optical narrow-band filters,dense wavelength-division-multiplexing devices and other correlative waveguide network devices.     

Beam Parameters for End Diffraction of TE0 Mode of Planar Waveguide

The relation between diffractive beam parameters and normalized frequency is analyzed that leads to two improved Tormulas for two kinds of mode-field halT-widths and several formulas for divergence angle as well as beam propagation factor. The numerical calculation indicates that the maximal relative error is less than 0.5% within a reasonable parameter range.     

Design of periodic metal-insulator-metal waveguide back structures for the enhancement of light absorption in thin-film solar cells

To increase the absorption in a thin layer of absorbing material (amorphous silicon, a-Si), a light trapping design is presented. The designed structure incorporates periodic metal-insulator-metal waveguides to enhance the optical path length of light within the solar cells. The new design can result in broadband optical absorption enhancement not only for transverse magnetic (TM)-polarized light, but also for transverse electric (TE)-polarized light. No plasmonic modes can be excited in TE-polarization, but because of the coupling into the a-Si planar waveguide guiding modes and the diffraction of light by the bottom periodic structures into higher diffraction orders, the total absorption in the active region is also increased. The results from rigorous coupled wave analysis show that the overall optical absorption in the active layer can be greatly enhanced by up to 40%. The designed structures presented in this paper can be integrated with back contact technology to potentially produce high-efficiency thin-film solar cell devices.     

基于硫堇掺杂的聚乙烯醇薄膜的光波导传感器检测硫化氢气体

采用旋转甩涂法将硫堇掺杂的聚乙烯醇薄膜固定在K⁺交换玻璃光波导表面,研制出一种高灵敏硫化氢气体传感器。 传感膜与硫化氢(H₂S)气体作用时,薄膜颜色从紫色变为无色,从而降低薄膜对倏逝波的吸收,使传感器的输出光强度（信号）增强。 采用流动注射法对H₂S气体进行检测。 实验结果表明,H₂S传感器对浓度在0.14~56 mg/m3范围的H₂S气体具有良好的线性响应（r=0.99667）,检出限为0.11 mg/m³(S/N=3),相对标准偏差为4.0%,响应时间（t90）＜2 s。 该传感器具有灵敏度高、响应快、可逆性和重复性好等特点。