Metalens are planar lenses composed of the subwavelength arrays, which have unconventional and versatile functionalities to manipulate the light fields compared with the traditional lens. It is noted that the most metalens are designed in a monochromatic mode in the visible or mid-infrared range (mid-IR), however, the broadband range is needed in many practical applications, such as spectroscopy, sensing, and imaging. Here, we design and demonstrate a broadband achromatic dielectric metalens in the mid-IR range of 4 μm - 5 μm for near diffraction-limited (1.0λ) focusing. The broadband achromatic propagation and focusing of the metalens are designed and simulated by constructing and optimizing the phase profile. The Pancharatnam-Berry (P-B) phases of all the elements contribute to the main phase increment of the whole phase profile of the metalens. The additional phase is constructed and optimized by using the random search algorithm to obtain the optimized size of all the elements. The focusing efficiency of the achromatic metalens is also optimized and averaged as the result of phase optimization within a wide band for the building elements, while it is lowered comparing with the regular metalens without broadband achromatic designing. Using this combined designing approach, various flat achromatic devices with the broadband metalens can find a new way for full-color detection and imaging.

大气碳同位素在环境污染源汇示踪和地球化学发展等方面的应用越来越广泛, 在其探测技术方面, 激光吸收光谱技术具有体积小、 可在线、 灵敏度高等优点, 在气体同位素探测中越来越受到重视。 工作中研究了2.7 μm波段的分布式反馈激光器(distributed feedback laser, DFB)可调谐半导体激光器的性能, 在遵循12CO2和13CO2同位素分子吸收谱线特征和同位素分子谱线选择原则的基础上, 确定了合适的激光器输出波长。 结合光程390.3 m的新型多次反射池, 实现了大气中CO2分子的δ13C同位素丰度探测。

Mid-infrared (mid-IR) (2 – 20 μm) photonics has numerous chemical and biologic “fingerprint” sensing applications due to characteristic vibrational transitions of molecules in the mid-IR spectral region. Unfortunately, compared to visible light and telecommunication band wavelengths, photonic devices and applications have been difficult to develop at mid-IR wavelengths because of the intrinsic limitation of conventional materials. Breaking a new ground in the mid-IR science and technology calls for revolutionary materials. Graphene, a single atom layer of carbon arranged in a honey-comb lattice, has various promising optical and electrical properties because of its linear dispersion band structure and zero band gap features. In this review article, we discuss recent research developments on mid-IR graphene photonics, in particular ultrafast lasers and photodetectors. Graphene-photonics-based biochemical applications, such as plasmonic sensing, photodynamic therapy, and florescence imaging are also reviewed.

建立了一种高质量、高效率全固态中红外激光系统，并对激光输出的效率、光束质量等指标进行了测试。首先，以二极管激光器为泵浦源，Tm3+∶YAP晶体为增益介质，搭建了输出波长为197 μm的近红外激光器。然后，以Tm3+∶YAP激光器为泵浦源，自行开发研制的Cr2+∶ZnSe单晶为增益介质，搭建了全固态中红外激光器。最后，测试了全固态中红外激光器的光束质量及激光器出光效率，并对谐振腔光效率的理论输出值与实际的激光器出光参数进行了对比。实验结果表明: 此全固态中红外激光器的光光转换效率为172%，斜率效率为20%，在最高输出能量为3 W时的光束质量(M2)在x和y方向分别为17和173，光束基本为圆形的高斯光斑。

3～5 μm中红外激光处于大气传输窗口，在分子光谱学、环境遥感、工业加工、空间通讯、光电对抗等领域有重要的应用前景。过渡金属掺杂II-VI族硫化物晶体可以直接实现中红外激光输出，是最有前途的技术途径之一。具有优良物理特性和光谱特性的Fe:ZnSe晶体是高效、宽带可调谐中红外激光介质的有力竞争者，介绍并分析了Fe:ZnSe晶体的光谱特性及其制备方法，综合评述了Fe:ZnSe激光技术的发展历程和最新研究进展，指出制备高光学质量的Fe:ZnSe晶体和研制3 μm波段高效、高能窄脉冲泵浦源是发展实用室温Fe:ZnSe激光器当前面临的挑战。并对实现室温高能、高功率Fe:ZnSe激光的关键问题进行了讨论。