Nonlinear effect of quantum electrodynamics for experiments with a ring laser

A new test to observe the effects of nonlinear electrodynamics in a vacuum is proposed, which can be carried out with modern ring lasers. An analysis of polarization and amplitude-phase correlation for a plane wave in a const ant and homogeneous external electromagnetic (EM) field is undertaken. It i s shown that if a part of the ring laser path is situated in a constant EM field, separated from the rest of the path by gas-impenetrable transparent partitions, and a vacuum maintained in this region, then in this laser four EM waves with different frequencies will propagate towards each other. In the general case, each of these waves is linearly polarized. A calculation of the difference of generation frequencies was performed as a function of the strength of the constant EM field. It was shown that this difference is more than an order greater than the present frequency resolu tion in a ring laser. A sketch of a possible experimental setup for the det ection of this effect is given.