研究目的
Investigating the non-linear response and energy absorption in bulk silicon irradiated by intense 12-fs near-infrared laser pulses, distinguishing between two regimes of non-linear absorption based on laser intensity, and examining the effects of bulk plasmon resonance excitation on energy transfer and optical reflectivity.
研究成果
The study concludes that for laser intensities near and above 1014 W/cm2, photoionization creates a dense plasma of electron-hole pairs in silicon, leading to a strongly absorbing state for near-infrared wavelengths. The energy transferred to electrons exceeds the thermal melting threshold of silicon, and the optical reflectivity of the photoexcited silicon is in good qualitative agreement with experimental data. The model highlights the competition between band filling, Pauli blocking, and Drude free-carrier responses in determining the optical properties of the photoexcited solid.
研究不足
The study is theoretical and relies on numerical simulations, which may not fully capture all physical phenomena observed in experimental settings. The model assumes a single-active electron approximation and uses an empirical pseudopotential method, which may simplify the complex interactions in the system.
1：Experimental Design and Method Selection:
The study employs a theoretical and numerical approach to investigate the non-linear response of bulk silicon to intense near-infrared laser pulses. The methodology includes solving the Schr?dinger equation in the single-active electron approximation and using the empirical pseudopotential method to model the periodic ionic lattice potential.
2：Sample Selection and Data Sources:
The study focuses on bulk silicon, with the band structure and optical properties modeled using the pseudopotential method.
3：List of Experimental Equipment and Materials:
The study is theoretical, focusing on numerical simulations rather than physical experiments, so specific equipment and materials are not listed.
4：Experimental Procedures and Operational Workflow:
The numerical simulations involve propagating Bloch wave-functions forward in time using the Cayley transformation, evaluating the single-particle density matrix, and updating the macroscopic vector potential based on the current density.
5：Data Analysis Methods:
The analysis includes calculating the absorbed energy, conduction electron density, and optical constants (refractive index, extinction coefficient) of the photoexcited silicon, and comparing these with existing experimental data.
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