基于切伦科夫型高阶谐波的超快任意光波形合成研究

Ultrafast optical field waveform generation and measurement is an emerging technology of significant impact because it affords a capability to attain microscopic control of electronic motion in the attosecond time scale. One of the most challenge during the synthesis is the generation of broadband high efficiency frequency comb. Here, we propose to realize optical field waveforms synthesis by nonlinear Cerenkov high order harmonic generation. Using ultraviolet crystal interface reflection phase matching and constructive interference scheme，one can achieve expanding harmonic spectrum and improving the harmonic efficiency， which promise high efficiency and high fidelity in ultrafast optical waveform synthesis. The experimental installation has the advantages of simple structure, high stability, small volume and low cost, which provides a theoretical and technical support for the subsequent development of integrated commercial optical function generator and with important research and application value.

超快任意光波形合成技术是实现在亚飞秒到阿秒尺度下操控电子微观行为的重要手段之一。其中，产生宽频带高效率的频率梳是影响光场合成效果的关键因素。本课题旨在研究基于非线性切伦科夫（Cerenkov）型高阶谐波实现超快任意光波形合成过程。利用紫外晶体界面反射型相位匹配的Cerenkov高阶谐波产生和高阶谐波相长干涉的方案，实现拓展谐波频谱范围、提升谐波效率，从而实验上完成高效率、高保真度的超快光场波形合成。本项目实验装置结构简单、系统稳定性高、体积小、造价低，可为后续研制集成商业化的光函数发生器提供理论及技术支持，具有重要的科研和应用价值。

拓展高次谐波频率范围、提高谐波转换效率对于实现切伦科夫型光场合成十分重要。项目系统研究并建立了描述三维非线性晶体中非线性过程的统一理论模型，并形成了相应的数值模拟能力。实验上通过晶体表面结构和实验参数的合理设计，在周期极化非线性晶体表面及周期非线性界面上，分别演示了切伦科夫辐射角度调控及相干增强的效应。开展紫外波段切伦科夫辐射研究，实现了紫外谐波辐射强度5到13倍的增强。通过傅立叶光谱合成算法对各阶谐波的相对振幅及相位进行设计，形成了不同波形的超短脉冲光谱合成算法。本项目的研究为实现任意波形超短脉冲奠定了基础。