Abstract

The far-field profile of high-order harmonics produced during high-field, laser atom interactions are determined by the atomic response and the phase-matching in the medium.¹-⁵ We have continued our studies of the harmonic far-field profiles which are designed to separate the different phase effects that determine the harmonic far-field profile. The primary phase effects are the phase-mismatch introduced by the radius of curvature of the phase front of the laser and the harmonics in the focus, the phase shifts from the group-velocity dispersion due to the indices of refraction of the atomic medium and of free electrons, the Guoy phase-shift through the focus, and the phase of the atomic dipole response. The Guoy phase-shift dominates the amplitude of the harmonic emission at the exit of the medium, but it is independent of radius and, hence, does not affect the far-field profile. By suitable choice of the experimental parameters, we have separated the atomic response, GVD, and the radius of curvature.

© 1994 Optical Society of America