Reciprocity and conjugation fidelity in double phase conjugate mirrors

摘要

Abstract: It is well known that the conservation of energy in an optical system can be described by an invariant (intensity of the optical wave) during propagation. We identically show that reciprocity can be described by an invariant. This invariant is the overlap integral of two counterpropagating waves, that stays constant in every place of a reciprocal optical system. Applied to the double phase conjugate mirror (DPCM) this invariant can be rewritten as an equality between the ratio of the conjugation fidelity of the two ports of the DPCM and the ratio of the transmission in intensity of the two beams. If restricted to a plane wave case this relation becomes the well known equality of the diffraction efficiencies in both directions. We have implemented an experimental set-up that allows to show that the double phase conjugate mirror is reciprocal what confirms all the above discussion. We use the same set-up to measure the conjugation fidelity of the DPCM. !18