Effects of spectral diffusion on the third-order nonlinear susceptibility for two- and three-level quantum systems, immersed in a thermal reservoir, are evaluated with a four-wave mixing (FWM) signal through the density matrix formalism. For this, inhomogeneously broadened two- and three-level quantum systems are used. In these models, the distribution of natural frequencies follows a Lorentzian function. The absorptive and dispersive nonlinear optical responses are determined for the considered quantum models. The results presented in this work show potential applications in the development of optical switches and provide a potential method to measure spectral diffusion relaxation times in three-level quantum systems.

中文翻译：

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四波混频信号中光谱扩散对二态和三态量子系统非线性光学特性的影响

通过密度矩阵形式用四波混合 (FWM) 信号评估光谱扩散对浸入热储层中的两级和三级量子系统的三阶非线性磁化率的影响。为此，使用了非均匀展宽的二能级和三能级量子系统。在这些模型中，自然频率的分布遵循洛伦兹函数。对于所考虑的量子模型，确定了吸收和色散非线性光学响应。这项工作中提出的结果显示了在光开关开发中的潜在应用，并提供了一种测量三能级量子系统中光谱扩散弛豫时间的潜在方法。