Abstract

An intense laser beam may leave the nonlinear thermal absorbing self-defocusing medium at different angles. In the far field the initial Gaussian beam acquires a ring angular structure described by the Airy functions.¹ Analysis of the derived expressions shows that the aberrational rings appear when the initial beam divergence is doubled θ_N ≃ θ₀; in the beam center the core, a circle of uniform amplitude and angle radius of ~2θ₀, is conserved.² The main fraction of the power is in the external ring (m = 1). In contrast to the nonaberrational case, the dependence of this defocusing on power is nonlinear. When the system changers from nonaberrational defocusing to aberrational defocusing, the intensity ratio between the beam center area and the external ring decreases drastically.

© 1987 Optical Society of America