Knowledge Bank

We have found that when the beam of a giant pulsed ruby laser is brought to a focus inside liquids or fused quartz about $10-13$ of the incident energy emerges as scattered radiation near twice the laser frequency. The amount of scattered radiation was found to vary as the square of the laser intensity. Further, it was observed to occur only in the focal region of the laser beam. Inelastic scattering, with frequency displacements characteristic of the material, as well as elastic scattering occurred. Both types of scattering depend upon different properties of the material than their linear counterparts, Rayleigh and Raman scattering. Thus, this nonlinear scattering provides an important new tool for the study of molecular structures and their interactions in liquids. The details of the experimental arrangement used, the data obtained and the theory for second order nonlinear scattering will be discussed. Planned improvements in the experimental arrangement and results from our present attempts to detect nonlinear scattering in crystals and gases will also be discussed.