Technique for determining the refractive indices and oscillator strengths with the angle phase‐matching conditions in optical four‐wave sum‐mixing

Abstract

AbstractA new method is proposed for measurement of the index of refraction of gas and oscillator strength. In four‐wave sum‐mixing in such nonlinear media as metal vapor or rare gas using the third‐order nonlinear optical effect, the refractive index of a nonlinear medium at the sum frequency in the vacuum ultraviolet range is found from the angle phase‐matching condition for the maximum conversion efficiency, and the oscillator strength is determined from the measurement of refractive index by the phase matching in terms of the sum frequency. The present method in which the refractive index and the oscillator strength are determined from the incident angle of each wave satisfying the angle phase‐matching has the advantage of fewer measurement parameters compared to the conventional methods in which a phase‐matching is accomplished with a mixture of gases with ordinary and extraordinary dispersions. This is because no buffer gas is mixed. In addition, the measurement accuracy is found theoretically to improve in the region with a higher atomic density.