光开关半导体光子晶体和体半导体的空间均匀性
Spatial homogeneity of optically switched semiconductor photonic crystals and of bulk semiconductors
摘要：
本文讨论了自由载流子产生的脉冲激光场作为一种机制，切换的光学性质的半导体光子晶体和块体半导体在超快时间尺度上。对开关幅度、时间尺度、诱导吸收以及空间均匀性设定要求，特别是对于λ = 1550 nm处的硅。使用非线性吸收模型，我们计算载流子的深度分布，并定义一个均匀性长度l_hom。均匀性长度轮廓可视化的平面跨越的线性和双光子吸收系数。这样一个广义的均匀性图使我们能够找到最佳的开关条件，在泵频率接近v/c= 5000 cm^{-1}（λ = 2000 nm）。讨论了光子晶体中散射对均匀性的影响。我们实验证明了一个10%的折射率开关在体硅在230 fs的横向均匀性超过30微米。我们的结果是相关的开关调制器在没有光子晶体。
英文摘要：
This paper discusses free carrier generation by pulsed laser fields as a mechanism to switch the optical properties of semiconductor photonic crystals and bulk semiconductors on an ultrafast time scale. Requirements are set for the switching magnitude, the time-scale, the induced absorption as well as the spatial homogeneity, in particular for silicon at lambda= 1550 nm. Using a nonlinear absorption model, we calculate carrier depth profiles and define a homogeneity length l_hom. Homogeneity length contours are visualized in a plane spanned by the linear and two-photon absorption coefficients. Such a generalized homogeneity plot allows us to find optimum switching conditions at pump frequencies near v/c= 5000 cm^{-1} (lambda= 2000 nm). We discuss the effect of scattering in photonic crystals on the homogeneity. We experimentally demonstrate a 10% refractive index switch in bulk silicon within 230 fs with a lateral homogeneity of more than 30 micrometers. Our results are relevant for switching of modulators in absence of photonic crystals.
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