Ryan Peterson J, Hafizi Bahman, Jones Theodore G, Johnson Luke A, Gordon Daniel F, Chen Yu-Hsin, Ting Antonio
Opt Express. 2022 Dec 19;30(26):46944-46955. doi: 10.1364/OE.474104.
Stimulated Raman scattering is ubiquitous in many high-intensity laser environments. Parametric four-wave mixing between the pump and Raman sidebands can affect the Raman gain, but stringent phase matching requirements and strongly nonlinear dynamics obscure clear understanding of its effects at high laser powers. Here we investigate four-wave mixing in the presence of strong self-focusing and weak ionization at laser powers above the Kerr critical power. Theoretical analysis shows that the plasma generated at focus naturally leads to phase matching conditions suitable for enhanced Raman gain, almost without regard to the initial phase mismatch. Multidimensional nonlinear optical simulations with multiphoton and collisional ionization confirm the enhancement and suggest that it may lead to significantly higher Raman losses in some high-intensity laser environments.
受激拉曼散射在许多高强度激光环境中普遍存在。泵浦光与拉曼边带之间的参量四波混频会影响拉曼增益，但严格的相位匹配要求和强烈的非线性动力学使得在高激光功率下难以清晰理解其效应。在此，我们研究在高于克尔临界功率的激光功率下，存在强自聚焦和弱电离时的四波混频。理论分析表明，聚焦处产生的等离子体自然地导致适合增强拉曼增益的相位匹配条件，几乎无需考虑初始相位失配。包含多光子和碰撞电离的多维非线性光学模拟证实了这种增强，并表明在某些高强度激光环境中可能导致显著更高的拉曼损耗。
