High-order harmonic production in a jet of krypton or xenon gas is studied using a 1.053 microns wavelength laser. All the harmonics in the 9th to 31st range display approximately equal angular widths with cone angles that are approximately half that of the laser. Lowest order perturbation theory predicts the angular widths to decrease with harmonic order N to the -12. The study of highly nonlinear processes in an intense laser field has become a topic of great interest. Among the possible effects is harmonic production of the laser field. In atomic gases the dipole approximation predicts the presence of only odd harmonics. We have studied the angular distribution of high-order odd harmonics 9th through 31st and we find the results to be inconsistent with predictions of lowest order perturbation theory LOPT. As expected, the harmonics are present when linearly polarized light is used and absent with circularly polarized light.
This article is from 'Osa Proceedings of the Topical Meeting (5th) on Short -Wave Length Coherent Radiation: Generation and Applications Held in Monterey, California on 8-10 April 1991. Volume 11,' AD-A252 973, p23-27.