On a new method of obtaining highly collimated light beams using the wavefront reversal phenomenon
Andreev N.F. , Bespalov V.I. , Kiselev A.M. , Matveev A.Z. , Pasmanik G.A.
The possibility of obtaining, in the absence of a reference wave, radiation with a divergence that is close to diffraction-limited is suggested and demonstrated experimentally. The method consists of adding the frequencies of two light waves with complex-conjugate phase multipliers.