When PEMs are used with lasers as light sources, modulated interference effects may occur. These manifest themselves in the form of spurious signals at the fundamental and harmonic frequencies of the PEM. Modulated interference is not a problem with any light source other than lasers. This effect is caused by multiple reflections of the light beam at surfaces of the PEM optical element. This interference then, in turn, becomes modulated because the two parallel surfaces of the PEM optical element are in relative motion. Several straight-forward approaches have been developed with the phenomenon of modulated interference. Please click here for a discussion of solutions.
