Since the emergence of graphene, transition metal dichalcogenides, and black phosphorus, two-dimensional materials have attracted significant attention and have driven the development of fundamental physics and optoelectronic devices. Metal phosphorus trichalcogenides (MPX3${\mathrm{MPX}}_3$), due to their large bandgap of 1.3–3.5 eV, enable the extension of optoelectronic applications to visible and ultraviolet (UV) wavelengths. Micro-Z/I-scan (μ$\mathrm{\mu }$-Z/I-scan) and micro-pump-probe (μ$\mathrm{\mu }$-pump-probe) setups were used to systematically investigate the third-order nonlinear optical properties and ultrafast carrier dynamics of the representative material AgInP2S6${\mathrm{AgInP}}_2{\mathrm{S}}_6$. UV-visible absorption spectra and density functional theory (DFT) calculations revealed a quantum confinement effect, in which the bandgap decreased with increasing thickness. The two-photon absorption (TPA) effect is exhibited under the excitation of both 520 and 1040 nm femtosecond pulses, where the TPA coefficient decreases as the AgInP2S6${\mathrm{AgInP}}_2{\mathrm{S}}_6$ thickness increases. In contrast, the TPA saturation intensity exhibits the opposite behavior that the TPA saturation is more likely to occur under visible excitation. After the valence band electrons undergo photon transitions to the conduction band, the non-equilibrium carriers relax through non-radiative and defect-assisted recombination. These findings provide a comprehensive understanding of the optical response process of AgInP2S6${\mathrm{AgInP}}_2{\mathrm{S}}_6$ and are a valuable reference for the development of optoelectronic devices.

中文翻译：

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层状 AgInP2S6 中的微观非线性光学活动和超快载流子动力学

自从石墨烯、过渡金属二硫属化物和黑磷的出现以来，二维材料引起了人们的广泛关注，并推动了基础物理和光电器件的发展。金属磷三硫属化物 ( MPX 3${\mathrm{MPX}}_3$ ) 由于其 1.3–3.5 eV 的大带隙，可以将光电应用扩展到可见光和紫外 (UV) 波长。使用微Z/I扫描（μ$\mathrm{\mu }$ -Z/I-扫描）和微泵浦探针（μ-$\mathrm{\mu }$泵浦探针）装置系统地研究了代表性材料的三阶非线性光学特性和超快载流子动力学AgInP 2 S 6${\mathrm{AgInP}}_2{\mathrm{S}}_6$。紫外可见吸收光谱和密度泛函理论（DFT）计算揭示了量子限制效应，其中带隙随着厚度的增加而减小。在520和1040 nm飞秒脉冲的激发下表现出双光子吸收(TPA)效应，其中TPA系数随着AgInP 2 S 6${\mathrm{AgInP}}_2{\mathrm{S}}_6$厚度的增加而减小。相反，TPA 饱和强度表现出与可见光激发下更可能发生 TPA 饱和相反的行为。价带电子经历光子跃迁到导带后，非平衡载流子通过非辐射和缺陷辅助复合而弛豫。这些发现提供了对AgInP 2 S 6${\mathrm{AgInP}}_2{\mathrm{S}}_6$光学响应过程的全面理解，对光电器件的开发具有重要的参考意义。