Fine structure and periods in the spectra of light scattered parametrically in isotropic media

A periodic structure with intervals of 1–10 cm^–1 was observed over a wide range of frequencies in the light scattered from self-focusing filaments in optical glasses. These results were obtained on application of single picosecond pulses of λ = 1.06 μ wavelength. The periodic structure occupied the whole recorded range, which consisted of a narrow region near 1.06 μ and the complete visible region. The structure also exhibited large superimposed periods of the order of 20–40 cm^–1. These phenomena were due to the self-modulation of a strong wave in a nonlinear medium.