基于等离子体的非线性光学方法可打破传统光学中材料损伤阈值、晶体缺失和相位不匹配等限制，在产生相对论强度且波长可调的中红外脉冲方面具有独特优势。利用等离子体波的光子减速产生超强近单周期中红外脉冲源是当前最有效的方法之一。本项目将采用理论分析和数值模拟研究少周期激光在等离子体中的非线性传输过程，提出利用少周期激光获得可调谐近单周期中红外脉冲辐射的物理方案，建立少周期激光传输和中红外辐射产生的理论模型，深入分析激光带宽、频率啁啾、色散特征长度和等离子体密度分布与中红外辐射特征参量间的定量关系，获得辐射脉冲与等离子体波内电子之间的能量耦合关系及等离子体波的演化特征，从而设计大幅增强能量转化效率的优化方案。本研究工作有望为基于少周期激光装置开展中红外辐射实验研究提供理论参考和技术支撑。

The nonlinear optics plasma-based breaks the limitation of the traditional methods, such as the threshold of material damage, crystal defect and phase mismatch, and has an important advantage in the generation of ultra-intense mid-infrared pulse. Photon deceleration in laser wakefield is an effective method to generate near-single-cycle mid-infrared radiation source. In this project, tunable near-single-cycle mid-infrared pulse radiation driven by a few-cycle laser pulse is investigated theoretically and by using particle-in-cell simulations. By establishing a complete nonlinear theoretical model of the few-cycle laser propagations and the mid-infrared pulse radiation generations, the quantitative relationships between the characteristic parameters of the mid-infrared radiation and laser bandwidth, frequency chirp, characteristic dispersive length, plasma density profile would be obtained. The energy coupling between radiation and electrons and the evolution of plasma wave are discussed, and an optimal scheme to enhance energy conversion efficiency is proposed, which can provide the theoretical reference and technical support for the future experiments.