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.

Entangled photon pairs are crucial resources for quantum information processing protocols. Via the process of spontaneous parametric downconversion (SPDC), we can generate these photon pairs using bulk nonlinear crystals. Traditionally, the crystal is designed to satisfy a specific type of phase-matching condition. Here, we report controllable transitions among different types of phase matching in a single periodically poled potassium titanyl phosphate crystal. By carefully selecting pump conditions, we can satisfy different phase-matching conditions. This allows us to observe first-order Type-II, fifth-order Type-I, third-order Type-0, and fifth-order Type-II SPDCs. The temperature-dependent spectra of our source were also analyzed in detail. Finally, we discussed the possibility of observing more than nine SPDCs in this crystal. Our work not only deepens the understanding of the physics behind phase-matching conditions, but also offers the potential for a highly versatile entangled biphoton source for quantum information research.

采用溶剂挥发法，在室温条件下生长出掺不同浓度Mn⁴⁺的K₂TiF₆∶Mn⁴⁺红光晶体。样品在紫光区和蓝光区都表现出Mn⁴⁺的特征宽带激发，对应于其⁴A₂ → ⁴T₁和⁴A₂ → ⁴T₂能级跃迁。在蓝光激发下，所有晶体都呈现出一系列窄带红光发射，其中最强发射峰位于631 nm处。在这些晶体中，样品K₂TiF₆∶Mn⁴⁺ （13.18%）表现出最高效的红光发射，其内外量子效率分别高达97.2%和83.3%。值得一提的是，该样品表现出荧光负热猝灭效应，其在120 ℃时的红光发射强度是室温时的1.81倍。所得晶体与Y₃Al₅O₁₂∶Ce³⁺ （YAG∶Ce³⁺）组装的暖白光LED流明效率（LE）高达180.9 lm/W、色温低至3 859 K、显色指数为91.3。与β?SiAlON∶Eu²⁺组装成白光LED器件，LE也达101.5 lm/W，显示色域为NTSC （National Television System Committee）标准值的94%。因此K₂TiF₆∶Mn⁴⁺晶体在白光LED照明及显示领域具有潜在应用前景。

Cascaded holography coupled with the secret-sharing scheme has recently gained considerable attention due to its enhanced information processing and encryption capabilities. Here, we propose a new holographic iterative algorithm and present the implementation of cascaded liquid crystal (LC) holography for optical encryption. Each LC layer acts as the secret key and can generate a distinct holographic image. By cascading two LC elements, a new holographic image is formed. Additionally, we showcase the dynamic optical encryption achieved by electrically switching LCs with combined electric keys. This work may offer promising applications in optical cryptography, all-optical computing, and data storage.

圆偏振光是光矢量端点轨迹为圆的光，它在传播时光矢量的大小不变而振动方向随相位而改变。通常，非偏振光首先通过偏振片转化为线偏振光，再通过λ/4波片分解为左旋或右旋圆偏振光。这一物理过程所获得的圆偏振光能量损耗一般超过50%。而通过构筑聚集诱导发光手性液晶分子直接获得圆偏振光，可以获得高的荧光量子效率和大的不对称因子，有效降低了能量损耗。因此，聚集诱导发光手性液晶受到了研究人员的广泛关注。本文基于聚集诱导发光基团修饰手性液晶分子的设计与合成，以及手性聚集诱导发光分子体系掺杂向列相液晶这两类方法，综述了本领域的研究进展，讨论了聚集诱导发光液晶分子结构设计和聚集态的形成对圆偏振发光和聚集诱导发光性能的影响，展望了这种新型光学材料所面临的机遇和挑战。

设计研制了波长为1 064 nm的半导体激光器泵浦单频Nd∶YAG激光振荡及功率放大系统。仿真分析了激光晶体的端面温度分布，采用低掺杂浓度激光晶体和端面键合方式有效改善了晶体棒的端面热效应。激光振荡级采用环形腔内插入法拉第旋光器、偏振片、半波片和声光Q开关的方式，在重复频率25 Hz下获得了能量2.18 mJ、脉冲宽度63.2 ns的单向单频脉冲激光输出。经过一级放大后，最终获得了能量15.85 mJ、脉冲宽度62.7 ns的单频脉冲激光输出。