Although previously reported terahertz absorbers can achieve high-sensitivity refractive index sensing, the resonant peak is too broad, which leads to a low figure of merit (FOM). Transmissive sensors based on bound states in the continuum (BIC) can achieve high FOM, but they have some limitations in high sensitivity. Herein, we propose a periodic triple parallel metal bars structure to obtain high quality, a strong field, and multiple hot spots by the Friedrich–Wintgen BIC. Numerical results show the sensitivity and FOM can reach 1877 GHz/RIU and 665, respectively. Compared to the previously reported transmissive sensors based on BIC, the sensitivity has been greatly improved.

增强荧光发射可以提高荧光检测灵敏度、提高LED的亮度，在提高发光器件性能方面具有重要意义。由于金属结构在增强局域场、增强荧光发射方面具有很好效果，而柔性电介质材料具有灵活的可弯曲性特性，本文提出一种由金属-电介质-金属（MDM）组成的柔性结构以增强荧光发射。利用时域有限差分方法系统研究了该结构对量子点定向发射增强的影响。理论计算表明柔性MDM结构局部起伏和弧度对荧光增强起促进作用，且可以使位于结构中心位置量子点的量子效率增强约7倍。此外，还可以改变电介质的折射率和厚度从而实现目标波长的可调谐性。实验结果表明该柔性MDM结构对荧光增强有一定的促进作用，这一发现对未来的显示技术和柔性发光器件都有很大的价值，对高效柔性器件的开发应用具有一定的指导意义。

本文提出了一种纳流通道-谐振腔耦合结构，用于实现对荧光物质微位移的检测。在本文中，首先，使用时域有限差分法，研究了量子点偏振态及结构参数对荧光与结构耦合效果的影响，进而对结构进行优化；然后，通过测量耦合结构输出光功率的变化，实现对荧光物质微位移的检测；最后，对影响传感灵敏度的因素进行研究。结果表明，相比传统方法，纳流通道-谐振腔耦合结构的折射率处于2.8~3.3之内时，该结构都可以实现对荧光物质微位移的高精度准确传感，并且通过减小纳流通道与谐振腔的间距可进一步提高传感灵敏度。

A novel way to design arbitrarily shaped retro-reflectors by optics surface transformation is proposed. The entire design process consists of filling an optic-null medium between the input and output surfaces of the retro-reflector, on which the points have 180 deg reverse corresponding relations. The retro-reflector can be designed to be very thin (a planar structure) with high efficiency. The effective working angles of our retro-reflector are very large (from ?80 deg to +80 deg), which can, in principle, be further extended. Layered metal plates and zero refractive index materials are designed to realize the proposed retro-reflector for a TM polarized beam.