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Ultrafast energy absorption and photoexcitation of bulk plasmon in crystalline silicon subjected to intense near-infrared ultrashort laser pulses
摘要： We investigate the non-linear response and energy absorption in bulk silicon irradiated by intense 12-fs near-infrared laser pulses. Depending on the laser intensity, we distinguish two regimes of non-linear absorption of the laser energy: for low intensities, energy deposition and photoionization involve perturbative three-photon transition through the direct bandgap of silicon. For laser intensities near and above 1014 W/cm2, corresponding to photocarrier density of order 1022 cm?3, we find that absorption at near-infrared wavelengths is greatly enhanced due to excitation of bulk plasmon resonance. In this regime, the energy transfer to electrons exceeds a few times the thermal melting threshold of Si. The optical reflectivity of the photoexcited solid is found in good qualitative agreement with existing experimental data. In particular, the model predicts that the main features of the reflectivity curve of photoexcited Si as a function of the laser fluence are determined by the competition between state and band filling associated with Pauli exclusion principle and Drude free-carrier response. The non-linear response of the photoexcited solid is also investigated for irradiation of silicon with a sequence of two strong and temporary non-overlapping pulses. The cumulative effect of the two pulses is non-additive in terms of deposited energy. Photoionization and energy absorption on the leading edge of the second pulse is greatly enhanced due to free carrier absorption.
关键词： bulk silicon,optical reflectivity,photoexcited solid,near-infrared laser pulses,Drude free-carrier response,non-linear response,energy absorption,plasmon resonance
更新于2025-09-23 15:21:01
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Nonlinear Refraction of Dielectric Single Crystals under Excitation with Ultrashort Near-Infrared Laser Pulses
摘要： Nonlinear refraction in a number of crystals (KGW, KGW:Eu3+, Ba(NO3)2, BaWO4, PbMoO4, and CdWO4) that are promising for excitation of multifrequency stimulated Raman scattering is investigated by a single-beam Z-scan method. Picosecond laser pulses with a wavelength of 1064 nm generated by a YAG:Nd3+ laser were used for excitation of nonlinear optical processes. The values of n2 are compared depending on the type of the crystal, optical-axis orientation, and impurity concentration.
关键词： Z-scan method,Ultrashort near-infrared laser pulses,Dielectric single crystals,Nonlinear refraction,Stimulated Raman scattering
更新于2025-09-16 10:30:52