Lowest-order optical second-harmonic process in a two-level system

Abstract

The influence of various physical parameters on the lowest-order second-harmonic process in a model solid is investigated. The medium is assumed to consist of two-level atoms obeying a simple harmonic-oscillator velocity distribution. It is seen that a definite phase relationship between the incident and the emergent fields is necessary for efficient second-harmonic conversion. In addition, the second-harmonic field and the quality factor are seen to depend on parameters like thickness of medium, relaxation time, level population and motion of the atoms. A comparison is made between this process and parametric oscillations.