Doppler effects in the propagation of a few-cycle pulse through a dense medium

Abstract

This numerical study demonstrates that Doppler redshift exists in the reflected spectrum of a few-cycle pulse, propagating through a dense medium. It manifests itself in two different forms, a sharp low-frequency spike (LFS) located at the red edge of the reflected spectrum and a relatively broader redshift near the carrier frequency. With the variation of the laser and medium parameters, the dominant reflection mechanism changes between bulk generation of backwards propagation waves and nonlinear reflection near the front face. This leads to the manifestation of Doppler effect changing accordingly between the two different forms. This study unifies the physical mechanism behind the LFS and dynamic nonlinear optical skin effect, which enriches the theoretical explanation of the spectral redshift of few-cycle pulse propagation beyond the intrapulse four-wave mixing.

Generation of attosecond pulse pair in polar media by chirped few-cycle pulses

“…In the following demonstration of an APP generation, two theoretical models with and without propagation effects are introduced. One is the nonlinear Bloch equations model, which is solved by the fourth-order Runge-Kutta method, and the other is the Maxwell-Bloch equations model, which is solved by the finite-difference time-domain (FDTD) method combined with the predictor-corrector method [31][32][33]. In the whole paper, atomic units (a.u.)…”

Bragg reflection in a quantum periodic structure

“…First, we model few-cycle pulse propagation through a periodic structure with δ ¼ λ 0 ∕2. The corresponding MB equations can be solved by Yee's finite-difference timedomain discretization method for the electromagnetic fields [21,22] and the predictor-corrector method for the medium variables [9,23] . The results are shown in Fig.…”