A Gaussian beam of a neodymium laser (l = 1 μm) with a radial field distribution over the cross section: E = E0exp[-r2/(R2)] (R = 3 mm) and with a plane wavefront is incident on a plane-parallel plate with a thickness of d = 1 cm, made from a nonlinear substance, the refractive index of which depends on the intensity: n = n0 + n2E2 (n2 = 10-11 SGSE units). Estimate at what laser power it is possible to reduce the beam diameter (focusing) after passing through the plate.

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