Mode Conversion due to Fluctuations in a Lens-like Medium

Mode conversion due to fluctuations caused by the dielectric-constant inhomogeneities of gaussian autocorrelation in a lens-like medium is discussed. Mean-square value of the mode-conversion coefficient, i.e., the power occupation of the higher mode in the total converted power, is obtained by means of the perturbation technique with the assumption of the fluctuations being smaller than square-law variation of the dielectric constant. The results show that the mode conversion increases in an undulating manner along the length of the gaseous medium, and is proportional to the longitudinal correlation length, whereas it decreases as the transverse correlation length becomes larger.