Two-Photon Resonant, Optical Third-Harmonic Generation.

We have developed a theory for two-photon resonant, optical third-harmonic generation that treats the atomic medium dynamically. The macroscopic polarization induced in the medium by the fundamental field is shown to contain components that oscillate at both the fundamental and third -harmonic frequencies. The polarization acts as a source term in a set of coupled transport equations for the field amplitudes and phases. We have detected the third harmonic of 8853 (ANGSTROM) radiation using Cesium as the atomic medium. A ruby pumped infrared organic dye laser was developed to produce the fundamental field needed for the process. The low yield of the observed third-harmonic signal in our experiment is attributable to the incomplete phase matching in the medium and to collisional quenching of the excited state population due to high buffer gas pressures.