Optical absorption properties of laser-driven matter
Optical absorption properties of laser-driven matter
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DOI：
10.1103/physreva.98.063412
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发表时间：
2018-12-12
影响因子：
2.9
通讯作者：
Franco, Ignacio
中科院分区：
文献类型：
--
作者：
Gu, Bing;Franco, Ignacio
表征和控制远离平衡状态的物质是科学技术面临的重大挑战。在这里，我们发展了一个理论的电子材料的光学吸收驱动远离平衡共振和非共振激光。其中，通过Floquet分析精确地处理了物质与驱动光之间的相互作用，而探测光的影响在微扰理论中被捕获到一阶。所得方程与平衡吸收方程相似，但Floquet模扮演原始特征态的角色。采用该形式描述了在中等强度的非共振光（非微扰，但非电离）照射下模型纳米级半导体的光学特性。如图所示，非共振光可以可逆地将这种透明半导体转变为宽带吸收器，并在非常低的频率（类似于meV）下打开强吸收和受激发射带。此外，驱动材料的吸收光谱表现出由驱动光的光子能量能量间隔的周期性特征，反映了Floquet带的周期性结构。这些发展为理解和预测材料在电场作用下出现的光学特性提供了一个平台，并促进了具有理想光学特性的激光驱动材料的设计。
Characterizing and controlling matter driven far from equilibrium represents a major challenge for science and technology. Here, we develop a theory for the optical absorption of electronic materials driven far from equilibrium by resonant and nonresonant lasers. In it, the interaction between matter and the driving light is treated exactly through a Floquet analysis, while the effects of the probing light are captured to first order in perturbation theory. The resulting equations are reminiscent to those for equilibrium absorption but with the Floquet modes playing the role of the pristine eigenstates. The formalism is employed to characterize the optical properties of a model nanoscale semiconductor dressed by nonresonant light of intermediate intensity (nonperturbative, but nonionizing). As shown, nonresonant light can reversibly turn this transparent semiconductor into a broadband absorber and open strong absorption and stimulated emission bands at very low frequencies (similar to meV). Further, the absorption spectra of the driven material exhibit periodic features energetically spaced by the photon energy of the driving light that reflect the periodic structure of the Floquet bands. These developments offer a platform to understand and predict the emergent optical properties of materials dressed by the electric field of light, and catalyze the design of laser-driven materials with desired optical properties.