A theoretical treatment of the high-order harmonic generation by electrons undergoing collisions with ions in a plasma in the presence of two single-mode linearly polarized fields is presented. Except for polarization, the two radiation fields may have arbitrary parameters. The treatment is based on an approximate solution of the Fokker–Planck equation for the plasma electron velocity distribution function. A set of representative numerical calculations is carried out. It is found that the generation of odd harmonics of each field is followed by the generation as well of satellites at mixed frequencies. For a given odd harmonic of one field, the satellites are shifted from it by multiple numbers of twice the frequency of the other field. When there are no coincident frequencies among the generated ones, the intensity of the odd harmonics of one field is found to decrease owing to the action of the other field. When, instead, the satellite frequencies of low-order harmonics coincide with the frequencies of high-order harmonics, a considerable enhancement of the latter is predicted. It is shown also that the harmonic intensity and the polarization direction depend significantly on the angle between the polarization directions of the two mixing fields.
© 2000 Optical Society of America
G. Ferrante, M. Zarcone, and S. A. Uryupin, "Harmonic generation and wave mixing in a plasma in the presence of two linearly polarized laser fields," J. Opt. Soc. Am. B 17, 1383-1389 (2000)