The intensities of Stokes and anti-Stokes waves generated parametrically in an atomic vapor excited by a dye laser are calculated. The threshold conditions for parametric oscillation are determined and the conditions for self-excitation of lasing are obtained when the atomic vapor is located in the laser resonator.
We present theoretically and experimentally a novel type of parametric fluorescence and oscillation in which four optical waves in off-axis, diagonal directions simultaneously build up under resonant counterpropagating pump-laser excitation in atomic sodium vapor. Two of the four are anti-Stokes shifted and the other two are Stokes shifted, and they are strongly coupled owing to electromagnetically induced diffraction. Theoretically, the Liouville-Maxwell equations are solved to derive four-wave propagation equations. Experimentally, we have observed four-wave parametric oscillation when a weak off-axis seed beam is introduced into otherwise axially symmetric parametric fluorescence patterns. Temporal waveforms are also analyzed, and strong correlations between any pairs of the four emissions are identified.
An investigation was made of the spectral properties of four-photon parametric oscillation when the frequency of the generated field is tunable near an atomic resonance line. An ω4 = ω1–ω2+ω3 generation process involving coherent anti-Stokes scattering in thallium vapor was achieved experimentally. Biharmonic pumping was provided by resonant excitation of a 6P1/2–6P3/2 two-photon transition at the frequency ω1–ω2. Measurements were made of the oscillation power when the frequency ω3 was tunable near the frequency of a 6P3/2–7D3/2 transition at various thallium vapor pressures. It was found that the spectral properties of resonant parametric oscillation depend strongly on the concentration of active-mixture atoms and also on various saturation effects.
A report is given of the first quantitative study of the spontaneous and stimulated electronic Raman scattering by a resonance doublet of the sodium atom excited resonantly at the D 1 and D 2 lines by a tunable dye laser. Theoretical and experimental analyses of the differential scattering cross section and polarization properties at the Stokes and anti-Stokes frequencies show that the observed scattering is due to a nearly resonant process involving the ground state 3 S 1/2 as the dominant intermediate state. The stimulated Stokes and anti-Stokes scattering lines, which are shifted from the D 1 and D 2 lines by an amount corresponding to the frequency separation between lowest-lying excited doublets 3 P 1/2 and 3 P 3/2 , are observed by exciting a sodium vapor cell with a passively mode-locked dye laser.
An effort was made to optimize the coherent anti-Stokes scattering four-photon parametric oscillation process in thallium vapor in the 277 nm range. The dependence of the stimulated emission power on the thallium vapor pressure, confocal parameter, detuning from two-photon resonance, and pump power was investigated. The considerable saturation of the parametric oscillation power observed both with respect to the pump power and the vapor pressure was attributed to the breakdown of the wave interaction as a result of the strong high-frequency Kerr effect under two-photon resonance conditions.