Search

The paper presents a method for simultaneous computation of eigenfunction and eigenvalue of the stationary Schrödinger equation on a grid, without imposing boundary-value condition. The method is based on the filter operator, which selects the eigenfunction from wave packet at the rate comparable to δ function. The efficacy and reliability of the method are demonstrated by comparing the simulation results with analytical or numerical solutions obtained by using other methods for various boundary-value conditions. It is found that the method is robust, accurate, and reliable. Further prospect of filter method for simulation of the Schrödinger equation in higher-dimensional space will also be highlighted.

The dynamics of nonlinear optical conversion in the high-intensity femtosecond pump regime has been studied in gaseous media over a wide pressure range. The existence of two different types of optical supercontinua, structured and structureless, has been found in a number of atomic (argon, krypton) and molecular (methane) gases. The structured optical supercontinuum exhibits a typical oscillationlike spectral structure, resulting from self-phase modulation in neutrals and plasma. The structureless optical supercontinuum is completely dense, and its main properties cannot be explained within the self-phase modulation mechanism. The structureless optical supercontinuum is attributed to Bremsstrahlung radiation from electrons that tunnel through the bound potential inside the atoms or molecules under a strong optical field. The basic properties of the structureless optical supercontinuum have now been revealed experimentally.

We investigate the possibility of optical pulse compression of high energy ultrashort laser pulses in an argon-filled planar waveguide, based on two level coupled mode theory and the full 3D nonlinear Schrödinger equation. We derive general expressions for controlling the spatial beam profile and the extent of the spectral broadening. The analysis and simulations suggest that the proposed method should be appropriate for optical pulse compression of ultrashort laser pulses with energies as high as 600 mJ.

The nonlinear susceptibility of atomic hydrogen interacting with an intense laser field has been investigated using a numerical solution of the time-dependent Schr\"odinger equation. It was shown that the behavior of the nonlinear susceptibility strongly depends on the intensity; it increases linearly in the low-intensity regime (Kerr regime), then saturates at a higher intensity. Furthermore, it was also shown that the nonlinear susceptibility is substantially induced by the ionization, whose magnitude is simply related to the density of the ionized electrons. By analyzing the calculated refractive index, it was found that the refractive index induced by ionization is 7--20 % smaller than that derived from the plasma frequency.

The propagation dynamics of intense femtosecond laser pulses in argon have been investigated theoretically and the results are compared with experimental data. It was found that in the initial stage the pulse propagates with the focal point moving ahead of the original one. The central beam of the trailing part experiences defocusing owing to ionization by the leading part and then regains self-focusing provided by power from the outer part. On propagating further, a quasistable balance is established between self-focusing and defocusing due to ionization-induced nonlinearity and diffraction, causing the beam to propagate in a self-guided mode. Furthermore, it was shown that the front of the split pulse decays faster, while the trailing edge experiences self-focusing and self-defocusing until a self-guided propagation mode is achieved. Multiple pulse splitting and shortening as a result of the dynamics near the focal point were also observed.

We investigate a simply corrected Keldysh-Faisal-Reiss (KFR) rate formula for laser-induced ionization of atoms in the nonperturbative intensity domain. Predictions of the formula are compared, first, with ab initio Floquet calculations, which show good agreement in the nonperturbative intensity domain for not too short wavelengths. Second, they are found to agree with the results of numerical simulations for the H atom, provided the pulse lengths are not shorter than three field cycles, so that the adiabatic rate becomes a valid parameter. Finally, total single-ionization yields predicted by the present model are compared with 36 different experimental data sets for He, Ne, Ar, Kr, and Xe, covering both linear and circular polarizations, and different wavelengths, pulse durations, and intensities; the results show a remarkable overall agreement with the data.