High spatial frequency evanescent wave holographic recording in photopolymers

Abstract

In the present work we report the results of holographic recording with two contra-propagating evanescent waves in photopolymers. The spatial frequency of the recorded permanent grating is 6380 mm−1 (grating step 156.7 nm) and 0.015% diffraction efficiency at 514.5 nm is achieved. The angular selectivity of the recorded evanescent grating is investigated at 632.8 nm. The maximum diffraction efficiency value is obtained at a critical angle of 60.1° ± 0.2° to the boundary with the total internal reflection prism, that determines the average refractive index of the grating of 1.501 ± 0.003. This is in good agreement with independent refractometric measurements and with theoretical expectations. A simple theoretical analysis of the evanescent wave holographic recording is made taking into account weak light absorption by the recording second medium. The close analogy with the attenuated total internal spectroscopic method is emphasized.