On the interpretation of interferograms of cavity turbulence

It is pointed out that lasers generally require an excellent medium uniformity to achieve diffraction-limited beam quality. This is especially important for potential high-energy gas lasers in which the product of the cavity length and gas density is large. The two factors that contribute to the degradation of beam quality are nonuniform intensity distributions and phase aberrations caused by ordered and random medium inhomogeneities. Usually the effect on beam quality of the last two is predicted on the basis of interferometric measurements of the cavity medium. The study presented seeks to determine the relation between the measured interferometer data and the scattering properties of the turbulence of the cavity medium. This is effected by comparing the far-field energy distribution that would be calculated from an interferogram with that calculated by the scattering of the cavity medium turbulence.