Abstract

Two sources of phase aberrations during amplification by stimulated Raman scattering have been studied. Both are caused by intensity nonuniformity in the incident pump laser beam. First, nonuniform population transfer of molecules undergoing the Raman transition results in a cumulative refractivity nonuniformity associated with the difference between the polarizabilities of the two molecular states. As shown experimentally by Butylkin et al.¹ and Baklushina et al.,² the fractional polarizability difference for the Q(1) vibrational transition of H₂ is ≃ 0.15–0.20. As a result, this effect becomes large at a fluence nonuniformity level >3 J/cm².

© 1986 Optical Society of America