ABSTRACT
The invention of lasers in the early sixties triggered the development
of the rich field of nonlinear optics. Similarly, the development of
lasers with ultrahigh intensities, that is, when the light electric
field is larger than the attraction between electrons and nuclei,
has boosted extreme nonlinear optics to a relevant and promising
discipline in physics. Besides its technological potentialities, strong
field physics is also challenging at a fundamental level, leading to the
reconsideration of the basic processes of light-matter interactions.
Also, the complexity of the exact solutions of the nonperturbative
equations has encouraged the development of simple approaches
based in semiclassical concepts that offer invaluable insight into the
basic processes involved. In this sense, Bohmian trajectories offer
an interesting extension of the semiclassical treatment, since their
description is purely quantum and , yet, they retain the intuitiveness
of a classical description. In this chapter we study the interaction
of a hydrogen atom with short and intense laser pulses. By first
using a simplified one-dimensional model, we show how Bohmian
trajectories can be used in the calculation of the above-threshold
ionization (ATI) and harmonic generation spectra. We also present
a full three-dimensional (3D) model to study the interaction of an
atom with beams bearing orbital angular momentum (OAM) and
use the trajectories to gain physical insight into the absorption of
angular momentum.
