Fabry–Perot resonator with volume-distributed phase inhomogeneities

The Born approximation is used to solve the problem of the influence of inhomogeneities of the refractive index of a medium filling a resonator on the resonator parameters. The attention is concentrated on finding the effective optical path (phase fluctuations) allowing for diffraction, which should give the expression for the Q factor of a resonator with an inhomogeneous medium. It is shown that diffraction has a positive influence reducing the role of distributed homogeneities and thus increasing the Q factor.