太赫兹场调制准相位匹配高次谐波产生

Terahertz Field Modulated Quasi-Phase-Matched High-Order Harmonic Generation

在高次谐波产生过程中,相位匹配是提高其产生效率的必备技术。传统相位匹配技术在各向同性的气体介质中无法实现,而准相位匹配技术作为一种可行的替代方案,可以突破高次谐波产生过程中相干长度的限制,实现谐波强度随传播距离持续增加。采用准连续的逆向传播太赫兹光场调制高次谐波的产生过程,以实现准相位匹配;通过模拟计算探讨了谐波光谱与调制场参数之间的关系,结果发现获得准相位匹配的光子能量与太赫兹调制场波长成反比,与调制场场强、泵浦激光场强的比值成正比。

Phase-matching is necessary to improve the efficiency of high-order harmonic generation.However,traditional phase-matching cannot be achieved in isotropic gas medium.As a feasible alternative,quasi-phase-matching breaks through the limitation of coherent length,which enables the harmonic intensity to continuously increase with the propagation distance.In this study,a quasi-CW counterpropagating terahertz field is used to modulate the generation of high-order harmonics to achieve quasi-phase-matching.The relationship between the harmonic spectra and the parameters of the modulation field is discussed through simulation.Results show that the quasi-phase-matched photon energy is inversely proportional to the wavelength of the terahertz modulation field and is directly proportional to the ratio of the field strength of the modulation to the pump field.