Angular responses of the first diffracted order in over-modulated volume diffraction gratings
Journal of Modern Optics
Kogelnik's Coupled Wave Theory has been used for decades to predict the diffraction efficiency of volume diffraction gratings. Although this theory has been applied with success to volume diffraction gratings recorded under a great variety of experimental conditions, its predictions deviate from the actual behaviour whenever the hologram is thin or the refractive index is high. In these cases, it is necessary to use a more general Coupled Wave Theory (CW) or the Rigorous Coupled Wave Theory
... led Wave Theory (RCW). Both of these theories allow for more than two orders propagating inside the hologram. The difference between them is that in the CW theory the second derivatives that appear in the coupled equations are disregarded. The RCW doesn't incorporate any approximation and thus, since it is rigorous, permits judging the accuracy of the approximations included in Kogelnik's and CW theories. In this article a comparison between the predictions of the three theories for phase transmission diffraction gratings is carried put. Over-modulated diffraction gratings are also recorded in photographic emulsions in order to study the applicability of Kogelnik's Theory in this case. Good agreement between theory and experiment is found for both Kogelnik's and Rigorous Coupled Wave Theory formulations in the particular experimental cases studied.