Simulation model for the effects of nonlinear polarization on the propagation of intense pulse lasers

Vortex harmonic generation in indium tin oxide thin film irradiated by a two-color field

When a two-color Laguerre-Gaussian laser beam propagates through an indium tin oxide (ITO) material, the spatial distributions of odd- and even-order vortex harmonics carrying orbital angular momentum (OAM) are studied. The origin of vortex harmonics can be directly clarified by investigating their dependence on the incident laser field amplitude and frequency. In addition, it is shown that the spectral intensities of vortex harmonics are sensitive to the epsilon-near-zero nonlinear enhancing effects and the thickness of ITO materials. Thus the vortex harmonics can be conveniently tunable, which provides a wider potential application in optical communications based on high-order OAM coherent vortex beams.

Enhancement and redshift of vortex harmonic radiation in epsilon-near-zero materials

The harmonic radiation from a vortex laser field interacting with an epsilon-near-zero (ENZ) material is numerically investigated via solving the Maxwell-paradigmatic-Kerr equations. For a laser field of long duration, the harmonics up to the seventh-order can be generated with a low laser intensity (∼10⁹ W/cm²). Moreover, the intensities of high order vortex harmonics at the ENZ frequency are higher than at other frequency points due to the ENZ field enhancement effects. Interestingly, for a laser field of short duration, the obvious frequency redshift occurs beyond enhancement in high order vortex harmonic radiation. The reason is that the strong change of the laser waveform propagating in the ENZ material and the non-constant field enhancement factor around the ENZ frequency. Because the topological number of harmonic radiation is linearly proportional to its harmonic order, the high order vortex harmonics with redshift still possess the exact harmonic orders indicated by the transverse electric field distribution of each harmonic.

Frequency generation within the forbidden band gap: all optical Rabi-like splitting in photonic crystals and microcavities

Based on three-dimensional time domain numerical simulations of the nonlinear dispersive Maxwell equations, we find evidence of all optical splitting of defect states in a photonic band gap structure. The result is analogous to the well known Rabi splitting and optical nutation in atomic two-level systems, and can be used for controlled in-gap generation of optical frequencies. Photon-echo-like behavior and third harmonic generation are also investigated.

Observation of supercontinuum generation in the direct simulation of an intense laser pulse propagating in a neutral gas

The propagation of high power short pulse laser pulses in neutral gases is a surprisingly complex phenomenon. In order to study the detailed propagation dynamics a code has been developed which explicitly solves Maxwell's equations including the finite response time background neutral gas polarization and optical field ionization. In large scale two dimensional simulations of a high power laser pulse propagating in hydrogen-like gas the generation of ultrabroadband white light, the so-called supercontinuum generation, is observed.