Curvature sensing plays an important role in structural health monitoring, damage detection, real-time shape control, modification, etc. Developing curvature sensors with large measurement ranges, high sensitivity, and linearity remains a major challenge. In this study, a curvature sensor based on flexible one-dimensional photonic crystal (1D-PC) films was proposed. The flexible 1D-PC films composed of dense chalcogenide glass and water-soluble polymer materials were fabricated by solution processing. The flexible 1D-PC film curvature sensor has a wide measurement range of 33–133 m^-1 and a maximum sensitivity of 0.26 nm/m^-1. The shift of the transmission peak varies approximately linearly with the curvature in the entire measurement range. This kind of 1D-PC film curvature sensor provides a new idea for curvature sensing and measurement.

Electromagnetic topological chiral edge states mimicking the quantum Hall effect have attracted a great deal of attention due to their unique features of free backscattering and immunity against sharp bends and defects. However, the matching techniques between classical waveguides and the topological one-way waveguide deserve more attention for real-world applications. In this paper, a highly efficient conversion structure between a classical rectangular waveguide and a topological one-way waveguide is proposed and demonstrated at the microwave frequency, which efficiently converts classical guided waves to topological one-way edge states. A tapered transition is designed to match both the momentum and impedance of the classical guided waves and the topological one-way edge states. With the conversion structure, the waves generated by a point excitation source can be coupled to the topological one-way waveguide with very high coupling efficiency, which can ensure high transmission of the whole system (i.e., from the source and the receiver). Simulation and measurement results demonstrate the proposed method. This investigation is beneficial to the applications of topological one-way waveguides and opens up a new avenue for advanced topological and classical integrated functional devices and systems.

光子晶体分为简单光子晶体和复式光子晶体，激光全息法是制作复式光子晶体的重要方法之一，光束偏振在其中扮演着重要角色。利用具有一定对称性的四光束配置干涉产生复式光子晶体，通过Matlab编程进行数值仿真，系统研究了不同偏振组合 (包括单光束、双光束、三光束和四光束) 对复式光子晶体元胞形状及干涉对比度的影响。结果表明，各光束的偏振度及旋转角度均对复式光子晶体具有显著影响。在不同偏振条件下获得了一系列丰富的元胞形状，如波浪条纹、椭圆柱、锯齿状等。此外，发现当各光束均为线偏振光时具有最佳的干涉对比度。上述研究结果对制作特殊元胞的复式光子晶体和虚拟实验教学具有一定的理论指导意义。

本文对梯度折射率光子晶体的亚波长聚焦特性进行了研究。该光子晶体是由硅和圆形空气孔构成的平行平板，通过改变空气孔的结构来实现折射率的梯度渐变。采用时域有限差分（finite-different time-domain，FDTD）算法对光子晶体的聚焦过程进行仿真分析。研究发现，适当地修正光程差可以大大地提高聚焦效果，同时焦距和中心空气孔的结构对聚焦效果也有影响。综合以上3种要素，最终设计出的梯度折射率光子晶体平板可实现较好的亚波长聚焦效果，其中在光子晶体外部1.45 λ处的光斑最佳，半宽值可达到0.3447 λ。为了提升应用性能，设计了一个动态的调焦系统。在该光子晶体中加入半导体制冷片来调节温度，通过改变温度可以实现1.1374 λ～2.6264 λ的焦点调谐，同时焦斑半宽均小于0.4 λ。