Coherent frequency doubling in nonlinear nonhomogeneous elements
Andreev N.F., Bespalov V.I., Kiselev A.M., Matveev A.Z., Pasmanik G.A.
It is shown that in inhomogeneous crystals the frequency doubling can occur with a compensation for phase distortions. To achieve this, the wave front of the first harmonic must be inverted at the input of the nonlinear element relative to the wave front of the radiation that was transmitted through the crystal in the opposite direction.