Mechanophotonics: Flexible Single‐Crystal Organic Waveguides and Circuits

We present the one‐dimensional optical‐waveguiding crystal dithieno[3,2‐a:2′,3′‐c]phenazine with a high aspect ratio, high mechanical flexibility, and selective self‐absorbance of the blue part of its fluorescence (FL). While macrocrystals exhibit elasticity, microcrystals deposited at a glass surface behave more like plastic crystals due to significant surface adherence, making them suitable for constructing photonic circuits via micromechanical operation with an atomic‐force‐microscopy cantilever tip. The flexible crystalline waveguides display optical‐path‐dependent FL signals at the output termini in both straight and bent configurations, making them appropriate for wavelength‐division multiplexing technologies. A reconfigurable 2×2‐directional coupler fabricated via micromanipulation by combining two arc‐shaped crystals splits the optical signal via evanescent coupling and delivers the signals at two output terminals with different splitting ratios. The presented mechanical micromanipulation technique could also be effectively extended to other flexible crystals.     

The cascaded exponential-tapered multimode interference couplers based triplexer design for FTTH system

A novel compact triplexer, which consists of series cascaded exponential-tapered multimode interference couplers, is introduced in this paper. General self-image properties of the exponential-tapered multimode interference couplers are investigated thoroughly to fulfill the compact integrated triplexer. By combining four exponential-tapered MMI couplers, a novel compact 0.6 cm-long triplexer that is with ITU standard wavelength of 1310 nm, 1490 nm and 1550 nm for FTTH is achieved without requiring complicated design. And it can be fabricated by common planar lightwave circuit (PLC) technology. From the simulation results for wavelength of 1310 nm, 1490 nm and 1550 nm, the insertion losses are 0.34 dB, 0.9 dB and 1.17 dB, with isolations for each output waveguide ranging from 12.74 dB to 37.15 dB. The 3 dB passband widths for 1310 nm, 1490 nm and 1550 nm are 112.39 nm, 29.44 nm and 26.7 nm.     

Efficient coupling of light into and out of a photonic crystal waveguide via surface modes

In this paper, we show how the coupling of light into a photonic crystal waveguide can be greatly enhanced by creating a periodic modulation in the dielectric structure surrounding the entrance of the waveguide. In this way, surface modes supported by the system can funnel the light that impinges onto the surface into the interior of the waveguide. Moreover, we also demonstrate that the shape and direction of the beam that emerges from the structure can be tailored by constructing a periodic corrugation near the exit side of the waveguide.     

高性能三端口全光纤开关

提出采用２×２和３×３单模光纤耦合器组合成的马赫－陈德尔干涉仪来制作全光纤开关。解决了在连续熔融拉伸两个耦合器组成马赫－陈德尔干涉仪的过程中，由于干涉的作用而无法监视光功率来控制第二个耦合器的分束比的问题。并且由于是连续熔融拉伸，保证了两条单模光纤干涉臂长度的一致，从而提高了单模光纤马赫－陈德尔干涉仪的性能，使得用其做成的三端口压电陶瓷电控全光纤开关具有宽频带的特性，其最小交调达到３０ｄＢ，附加损耗为０．２３ｄＢ。     

3-D Electromagnetic Modeling of Polarization-Dependent Coupling Characteristics of 1×3 Linear Array Weakly Fused Fiber Couplers

Based on the full-wave surface integral equations method and the steplike approximation technique, a three-dimensional (3-D) electromagnetic model for simulating polarization-dependent power-coupling behavior of 1×3 linear array weakly fused fiber couplers is proposed. The accuracy of the proposed numerical model is confirmed to be good by comparing with the measured power transfer behavior at the fusing and elongating process of the couplers. In the 3-D modeling view, the polarization-dependent coupling behavior of two practical couplers, 1/3 power splitter and wavelength-flattened coupler, are numerically studied. It is seen that as the coupler is designed in a very weakly fused condition the polarization-dependent loss (PDL) is significantly increased. For designing the 1×3 coupler with low PDL, it is suggested that the aspect ratio has to be controlled in stronger fused range between 0.8 and 0.9.     

Waveguide sub‐wavelength structures: a review of principles and applications

Periodic structures with a sub‐wavelength pitch have been known since Hertz conducted his first experiments on the polarization of electromagnetic waves. While the use of these structures in waveguide optics was proposed in the 1990s, it has been with the more recent developments of silicon photonics and high‐precision lithography techniques that sub‐wavelength structures have found widespread application in the field of photonics. This review first provides an introduction to the physics of sub‐wavelength structures. An overview of the applications of sub‐wavelength structures is then given including: anti‐reflective coatings, polarization rotators, high‐efficiency fiber–chip couplers, spectrometers, high‐reflectivity mirrors, athermal waveguides, multimode interference couplers, and dispersion engineered, ultra‐broadband waveguide couplers among others. Particular attention is paid to providing insight into the design strategies for these devices. The concluding remarks provide an outlook on the future development of sub‐wavelength structures and their impact in photonics.

     

High impact shock testing of fiber-optic components

MIL-S-901 High Impact Shock tests were performed on commercial-grade and ruggedized fiber-optic connectors, splices, and switches. Both single-mode and multimode connectors and splices were tested. Only multimode switches were tested. Transient losses of varying magnitudes and durations were observed. Most components suffered no permanent degradation.     

Adjustment of the coupling ratio by laser ablation of Ti:LiNbO3 directional couplers

The coupling ratio of directional couplers in Z-cut Y-propagation and X-cut Z-propagation LiNbO₃ crystals was adjusted by laser ablation. The coupling ratio change is more efficient for the TM-mode of Z-cut couplers. The method can be used to correct the uncertainty of the coupling ratio for directional couplers that occurs during fabrication process.     

用有效折射率/有限元法设计1.55μmTi:LiNbO3单模条波导及其方向耦合器

应用有效折射率/有限元法(EI-FEM),考虑到LiNbO3晶体和Ti扩散的各向异性,折射率增量与寻常光、非寻常光及波长色散的关系,设计了1.55μm光波长下工作的z切y传播Ti:LiNbO3单模条波导的制备参数,计算和分析了其单模特性、模式场分布及其变化规律.扩展了EI-FEM,将其用于求解耦合波导系统,确定了方向耦合器的耦合长度及其波长色散特性.     

成色剂分子的~1H核磁共振谱研究

对20多种β双酮、吡唑酮及酚(包括苯酚)型的黄、品、青成色剂分子作了~1HNMR谱的测定和解析。并用INDOR技术和自旋模拟程序等确定了~1H化学位移和偶合常数。还对分子内的受阻旋转、活泼氢状态以及互变异构体的动力学现象作了讨论。