Electron stimulated Raman scattering and four-wave interaction in barium atomic vapor pumped by tunable ultrashort light pulses

A phosphate neodymium glass laser emitting picosecond pulses tunable in the 1.05–1.07 μ range was developed to study nonlinear optical processes in atomic barium vapor. Its temporal characteristics were investigated using a modified second harmonic beam method. Electron stimulated Raman scattering and four-photon parametric conversion in atomic barium vapor were used to obtain efficient conversion of the third harmonic of the picosecond phosphate laser (350–356 nm) to the Stokes (580–600 nm) and anti-Stokes (250–253 nm) waves. The highest conversion quantum efficiency for the Stokes wave was 15%. Electron stimulated Raman scattering in an (6s²)¹S–(6s7s)¹S–(6s6p)¹P⁰ system, having a strongly forbidden first transition, was recorded for the first time. In the same system, two-photon pumping generated four-photon parametric superradiance and it was found that the signal and idler waves had anomalously broad spectra (wider than 100 cm^–1).