This paper discusses free carrier generation by pulsed laser fields as amechanism to switch the optical properties of semiconductor photonic crystalsand bulk semiconductors on an ultrafast time scale. Requirements are set forthe switching magnitude, the time-scale, the induced absorption as well as thespatial homogeneity, in particular for silicon at lambda= 1550 nm. Using anonlinear absorption model, we calculate carrier depth profiles and define ahomogeneity length l_hom. Homogeneity length contours are visualized in a planespanned by the linear and two-photon absorption coefficients. Such ageneralized homogeneity plot allows us to find optimum switching conditions atpump frequencies near v/c= 5000 cm^{-1} (lambda= 2000 nm). We discuss theeffect of scattering in photonic crystals on the homogeneity. We experimentallydemonstrate a 10% refractive index switch in bulk silicon within 230 fs with alateral homogeneity of more than 30 micrometers. Our results are relevant forswitching of modulators in absence of photonic crystals.
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机译：本文讨论了通过脉冲激光场产生自由载流子的机制，以超快时间尺度切换半导体光子晶体和体半导体的光学特性。设置了开关量，时间尺度，感应吸收以及空间均匀性的要求，特别是对于λ= 1550 nm的硅。使用非线性吸收模型，我们计算载流子深度剖面并定义均一性长度l_hom。均匀长度轮廓在由线性和双光子吸收系数跨越的平面中可视化。这种一般化的均匀性图使我们能够找到泵频率在v / c = 5000 cm ^ {-1}（λ= 2000 nm）附近的最佳开关条件。我们讨论了光子晶体中的散射对均匀性的影响。我们实验证明了在230 fs内散装硅中的10％折射率转换，其侧面均匀性超过30微米。我们的结果与在没有光子晶体的情况下转换调制器有关。
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