Polychromatic phase conjugation in Fabry-Perot etalons

The field inside a Fabry-Perot etalon is calculated for the case when the entering beam has a Gaussian profile and is entering under an angle. The coupled wave equations describing polychromatic phase conjugation in a Fabry-Perot etalon are solved analytically in the undepleted pumps approximation. This solution shows that the power necessary to yield a certain reflectivity decreases an order of magnitude in correctly made etalons.<>