Reconstruction of light-beam wave fronts by stimulated Raman scattering

The experiments discussed demonstrated that the phenomenon of wave front reconstruction is observable not only in the excitation of stimulated Raman scattering by a single-mode laser but also in the case of a combined action of a Q-switched multimode ruby laser and a second-harmonic neodymium laser (6953 and 5300 A, respectively). Essentially, the phenomenon is as follows: at certain specific values of the pumping power and fluid layer thickness (liquid nitrogen was used in the experiments), the divergence and intensity distribution of the exciting beam and of the stimulated Raman beam in the 'backward' direction become very much alike, while the brightness of the Raman beam in this direction exceeds substantially that of the Raman scattered light propagating in the direction of the exciting radiation. The wave front of the exciting radiation is reconstructed at a wavelength that equals the most intense molecular vibration of the scattering medium.