Light propagation through inhomogeneous media with radial refractive index: application to thermal blooming

Abstract

Light propagation through inhomogeneous media whose refractive index has weak changes with cylindrical symmetry around the propagation axis is studied. Two approximations based on geometric optics are examined. Both are valid when the refractive index also depends on the axial coordinate. As an application of the above, thermal blooming of a laser beam when winds and convective currents are absent has been analyzed. The cylindrical TEM(00) and TEM(10) laser modes are considered, and explicit analytical expressions for the light rays and intensity profiles for short and long times are derived. Good quantitative (or qualitative) agreement with other previously reported numerical and experimental results has been obtained.