Self-conjugation of a speckle pump beam in a loop containing a photorefractive crystal

We show theoretically and experimentally that the optimum geometry for phase conjugation of speckle beams in a loop containing a photorefractive crystal is the "biting-its-own-tail" geometry with beam diameter preserved. We predict an increase in the threshold for the process by a factor of 1.5 due to the introduction of speckle in the beam to be conjugated.