Enhanced energy deposition and carrier generation in silicon induced by two-color intense femtosecond laser pulses
Enhanced energy deposition and carrier generation in silicon induced by two-color intense femtosecond laser pulses
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DOI：
10.1103/physrevb.106.195141
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发表时间：
2022-05
影响因子：
3.7
通讯作者：
M. Tani;K. Sasaki;Y. Shinohara;K. Ishikawa
中科院分区：
文献类型：
--
作者：
M. Tani;K. Sasaki;Y. Shinohara;K. Ishikawa
本文利用时变密度泛函理论（TDDFT）从理论上研究了双色飞秒激光脉冲作用下晶体硅的光能吸收。我们采用修正的Becke-Johnson （mBJ）交换相关势来再现实验直接带隙能eg。我们考虑一种颜色在高于eg的紫外线（UV）范围内，而另一种颜色在低于eg的红外线（IR）范围内的情况。在总脉冲能量守恒的情况下，以两种颜色的混合比η为函数考察了能量沉积。同时双色辐照显著增强了从激光脉冲到硅中的电子系统的能量传递，并在η ~ 0处达到最大。5. 增加的是产生的载流子的数量，而不是每个载流子吸收的能量。对于较低的红外光子能量，或等效地，较大的矢量电位振幅，效果更有效。作为潜在的机制确定了带内电子运动在价带（激发前）驱动的红外组分和共振价导带间激发（载流子注入）诱导的紫外组分之间的相互作用。前者增加了通过共振跃迁k点的可激发电子。不同的多光子吸收路径或在导带中产生的载流子带内运动的影响较小。
We theoretically investigate the optical energy absorption of crystalline silicon subject to dual-color femtosecond laser pulses, using the time-dependent density functional theory (TDDFT). We employ the modified Becke-Johnson (mBJ) exchange-correlation potential which reproduces the experimental direct bandgap energy E g . We consider situations where the one color is in the ultraviolet (UV) range above E g and the other in the infrared (IR) range below it. The energy deposition is examined as a function of mixing ratio η of the two colors with the total pulse energy conserved. Energy transfer from the laser pulse to the electronic system in silicon is dramatically enhanced by simultaneous dual-color irradiation and maximized at η ∼ 0 . 5. Increased is the number of generated carriers, not the absorbed energy per carrier. The effect is more efficient for lower IR photon energy, or equivalently, larger vector-potential amplitude. As the underlying mechanism is identified the interplay between intraband electron motion in the valence band (before excitation) driven by the IR component and resonant valence-to-conduction interband excitation (carrier injection) induced by the UV component. The former increases excitable electrons which pass through the k points of resonant transitions. The effect of different multiphoton absorption paths or intraband motion of carriers generated in the conduction band play a minor role.