The simplest approach to deal with light excitations in direct-gap semiconductors is to model them as a two-band system: one conduction and one valence band. For such models, particularly simple analytical expressions are known to exist for the optical response such as multiphoton absorption coefficients. Here we show that generic multiband models do not require much more complicated expressions. Our length-gauge analysis is based on the semiconductors Bloch equations in the absence of all scattering processes. In the evaluation, we focus on two-photon excitation by a pump-probe scheme with possibly nondegenerate and arbitrarily polarized configurations. The theory is validated by application to graphene and its bilayer, described by a tight-binding model, as well as bulk zinc-blende semiconductors described by $\mathit{k}·\mathit{p}$ theory.

中文翻译：

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半导体中的双光子吸收：多波段长度计分析

处理直接带隙半导体中光激发的最简单方法是将它们建模为双带系统：一个导带和一个价带。对于此类模型，已知存在诸如多光子吸收系数等光学响应的​​特别简单的解析表达式。在这里，我们展示了通用多波段模型不需要更复杂的表达式。我们的长度计分析基于没有所有散射过程的半导体布洛赫方程。在评估中，我们专注于泵浦探针方案的双光子激发，该方案可能具有非简并和任意极化配置。该理论通过应用于由紧束缚模型描述的石墨烯及其双层以及由$\mathit{ķ}·\mathit{p}$理论。