Abstract
ABSTRACT Using the formulism of perturbative nonlinear optics, we derived the general formula for generation of third- and fifth harmonic signals in inert gases by coherently controlled two-color laser pulses. There are three processes that contributed to third- and fifth harmonic signals. There are direct third- and fifth harmonic generation, four-wave mixing, and the interference between the two former processes. Key parameters affecting nonlinear conversion are phase matching or pressure of the gas, power ratio and relative phase of the two-color exciting light and focusing. The most effective way of nonlinear conversion is through optimization of the four-wave mixing process. High modulation depth of the generated harmonics is achieved by manipulating the interference term. Experimentally, the third harmonic (355 nm) signal excited by coherently controlled two-color (1064, and 532 nm) optical pulses in argon gas were found to be in good agreement with theoretical predictions.