Influence of ellipticity on harmonic generation

We present results of experiments testing the influence of elliptical polarization on the production of high-order harmonics. Experiments were conducted both with a 600-nm, 1-psec dye laser and with an 825-nm, 140-fsec Cr:${\mathrm{LiSAF}}_6$ (Cr:LiSAF) laser system, over a wide range of intensities and target gases (xenon, argon, and neon), using a detection system with a dynamical range of more than three orders of magnitude. The decrease of the harmonic strength with the ellipticity of the pump beam is rather slow for the low-order harmonics, and becomes much steeper for the high-order harmonics. We compare some of these data with the predictions of lowest-order perturbation theory.