Acceleration of light and soliton formation due to nonlinear absorption of femtosecond laser pulse energy by a medium containing nanorods

Superluminality phenomenon at a femtosecond laser pulse propagation in a medium containing nanorods

“…36 Our attention in this paper is attracted by the effects of superliminality, [41][42][43][44][45][46] as well as a soliton formation. It should be stressed that earlier 37 we showed that a fast light can appear in a medium with nanorods under the weak optical energy absorption on the pulse dispersion length while below, we show that the laser pulse propagation modes take place for a wide range of the problem parameters. In particular, we demonstrate that a fast light propagation mode occurs for various strengths of positive phase-amplitude grating induced by laser radiation, which correspond to the various detuning between wave packet carrier frequency and nanorod resonance frequency.…”

“…37, where a good quantitative agreement of a pulse center evolution, calculated using both the nonlinear geometric optics and computer simulation, was shown. Along the characteristics, Eqs.…”

“…We also investigate the soliton formation if a nonlinear absorption is close to the maximal value, which is achieved at absorption resonance of nanorods in dependence on their aspect ratio. In connection with this, it should be stressed that, in our previous papers, [35][36][37][38] we considered a linear dependence of light energy absorption on nanorod aspect ratio, which is valid far from the absorption resonance.…”

“…[26][27][28][29][30][31][32][33][34] However, such a laser pulse propagation mode for a chirped pulse has not been investigated enough yet, despite its wide appearance in a high intense femtosecond pulse propagation. In our previous papers, [35][36][37][38] we have investigated a femtosecond pulse propagation in a medium with nanorods under the conditions of both the nanorod ellipticity (aspect ratio) changing and dependence of two-photon absorption (TPA) on nanoparticle aspect ratio. In particular, using the density matrix formalism, we derived the equation set, which describes the femtosecond pulse propagation in the medium with nanorods reshaping, and obtained some analytical formulas for such propagation.…”

“…In particular, using the density matrix formalism, we derived the equation set, which describes the femtosecond pulse propagation in the medium with nanorods reshaping, and obtained some analytical formulas for such propagation. 37 In particular, we analytically derived the laws for laser pulse energy and intensity evolution if the laser pulse propagates in a medium with TPA or single-photon absorption (SPA) under the conditions of negligible second-order dispersion (SOD) influence. We also derived the laws for laser pulse amplitude and aspect ratio evolution in the framework of nonlinear geometric optics approximation if only a pure amplitude grating is induced by laser radiation in the medium with SPA.…”