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arXiv 1902.02673physics.opticscond-mat.mtrl-sci
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中红外飞秒laser脉冲辐照下硅的超快动力学和表面等离子体特性

Ultrafast dynamics and surface plasmon properties of Silicon upon irradiation with mid-infrared femtosecond laser pulses

E. Petrakakis, G. D. Tsibidis, E. Stratakis

摘要:

我们提出了一个尚未探索的超快过程和动力学的产生的激发载流子在中红外(中红外)光谱区域的飞秒脉冲激光照射硅后的理论研究。分析了在2.2 μm ~ 3.3 μm范围内不同波长λL下电子-空穴子系统和晶格子系统的载流子密度和热响应的演化,探讨了双光子和三光子吸收机制的影响。诱导克尔效应的作用是突出的,它表现出更明显的影响,在较小的波长在中红外范围。对激发表面等离子体激元(SP)的条件的研究表明,在材料表面形成了弱束缚SP波。所示的激发SP的寿命上升时,产生的波长增加一个大于一个预测的更高的激光频率。对不同脉冲宽度τp下的损伤阈值的计算表明,损伤阈值的增加遵循幂律(τ p^{λ L}),其增加率由指数λ L决定。对不同τp下的多光子吸收率和碰撞电离贡献的研究表明,当τp较长时,λL=2.5 μm的损伤比λL=2.2 μm的损伤小。

英文摘要:

We present a theoretical investigation of the yet unexplored ultrafast processes and dynamics of the produced excited carriers upon irradiation of Silicon with femtosecond pulsed lasers in the mid-infrared (mid-IR) spectral region. The evolution of the carrier density and thermal response of the electron-hole and lattice subsystems are analysed for various wavelengths λL in the range between 2.2 μm and 3.3 μm where the influence of two and three-photon absorption mechanisms is explored. The role of induced Kerr effect is highlighted and it manifests a more pronounced influence at smaller wavelengths in the mid-IR range. Elaboration on the conditions that leads to surface plasmon (SP) excitation indicate the formation of weakly bound SP waves on the material surface. The lifetime of the excited SP is shown to rise upon increasing wavelength yielding a larger than the one predicted for higher laser frequencies. Calculation of damage thresholds for various pulse durations τp show that they rise according to a power law (~τ_p^{ζ(λ_L) ) where the increasing rate is determined by the exponent ζ(λ_L). Investigation of the multi-photon absorption rates and impact ionization contribution at different τp manifests a lower damage for λL=2.5 μm compared to that for λL=2.2 μm for long τp.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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