基于非线性光学频率变换技术的可调谐中红外激光器在光电对抗、气体检测、生物医学等应用领域有着重要价值。近红外激光，尤其是1 μm激光直接泵浦的可调谐中红外激光器具有结构紧凑、调谐范围宽、稳定性高的优势。从非线性光学频率变换技术的核心器件——非线性晶体出发，综述新型非氧化型晶体在可调谐中红外激光产生中的应用现状，介绍了不同晶体的光学特性及实现中红外产生的方法。针对可调谐中红外激光源的调谐范围、单脉冲能量、重复频率等关键参数，分析了不同晶体的中红外产生性能及其适用的中红外产生方法。最后对近红外激光器泵浦的可调谐中红外激光器进行了展望。

The 4H-SiC crystal is found to have great potential in terahertz generation via nonlinear optical frequency conversion due to its extremely high optical damage threshold, wide transparent range, etc. In this paper, optical rectification (OR) with tilted-pulse-front (TPF) setting based on the 4H-SiC crystal is proposed. The theory accounts for the optimization of incident pulse pre-chirping in the TPF OR process under high-intensity femtosecond laser pumping. Compared with the currently recognized LiNbO₃-based TPF OR, which generates a single-cycle terahertz pulse within 3 THz, 4H-SiC demonstrates a significant advantage in producing ultra-widely tunable (up to over 14 THz, TPF angle 31°–38°) terahertz waves with high efficiency (~10^–2) and strong field (~MV/cm). Besides, the spectrum characteristics, as well as the evolution from single- to multi-cycle terahertz pulses can be modulated flexibly by pre-chirping. The simulation results show that 4H-SiC enables terahertz frequency extending to an unprecedent range by OR, which has extremely important potential in strong-field terahertz applications.

Terahertz (THz) technology offers novel opportunities in biology and medicine, thanks to the unique features of THz-wave interactions with tissues and cells. Among them, we particularly notice strong sensitivity of THz waves to the tissue water, as a medium for biochemical reactions and a main endogenous marker for THz spectroscopy and imaging. Tissues of the brain have an exceptionally high content of water. This factor, along with the features of the structural organization and biochemistry of neuronal and glial tissues, makes the brain an exciting subject to study in the THz range. In this paper, progress and prospects of THz technology in neurodiagnostics are overviewed, including diagnosis of neurodegenerative disease, myelin deficit, tumors of the central nervous system (with an emphasis on brain gliomas), and traumatic brain injuries. Fundamental and applied challenges in study of the THz-wave – brain tissue interactions and development of the THz biomedical tools and systems for neurodiagnostics are discussed.

研究了目标物体的单光子散射回波特性，基于红外单光子探测器和皮秒激光器搭建了目标光学散射特性测量系统，以回波光子数作为单光子条件下目标光学散射特性的表征。实验研究了不同形状（球体、立方体、圆柱体、圆锥体）目标物体的单光子散射特性，并利用双向反射分布函数模型对实验结果进行拟合，理论拟合结果与实验测量结果能够很好地吻合。进一步对不同材质（瓷砖、木材、外墙砖）目标物体的单光子散射特性进行了研究，并将实验结果与传统波动散射特性进行了对比分析。该研究为单光子激光雷达远距离目标识别与探测的相关工作提供了参考。

为实现面向自适应激光无线传能应用的大范围免调试激光器，对基于猫眼逆反射器的端面泵浦Nd: GdVO₄激光器开展实验研究；在补偿接收端的球差和场曲、优化激光器工作距离和接收端视场的基础上，分析发现发射端各透镜的场曲所导致的猫眼逆反射器离焦是限制其视场角度（接收端离轴量容限）的主要因素。基于Zemax软件对发射端场曲进行分析计算，并设计加工了矫正场曲的非球面透镜以避免接收端离轴情况下的发射端离焦，实现优化发射端视场的目的。使用优化设计的非球面透镜后，在5 m的长工作距离下激光器4.6°发射端视场内的输出功率均在其最高输出功率的50%以上，相比使用普通球面透镜时的结果得到显著的提升。对比理论设计和实验结果仍有一定差距，认为补偿激光晶体热透镜的像差是进一步优化发射端视场的关键。

A multi-lens retroreflector with field curvature compensation was designed and used in an alignment-free distributed-cavity laser with a long working distance for resonant beam charging applications. The multi-lens design, which makes use of off-the-shelf components, also allows a large field of view (FoV) without requirement of large element aperture. By implementing this design, an end-pumped 1063 nm Nd:GdVO4 laser could deliver over 5 W continuous-wave output power over a large range of working distances (1–5 m) and with ±30° receiver FoV under an incident diode pump power of 16.6 W. The output power fluctuation was less than 10% when moving and tilting the receiver over such a large range, without requiring any realignment of the cavity.