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Low spatial frequency grating recorded in photopolymer material

Various photopolymer materials have recently found a significant number of useful applications in microelectronics and the PC board industries. Some of these materials have also become attractive optical recording materials for the recording of holographic devices such as diffractive optical elements and gratings, or as data storage media, for the fabrication of optical waveguides and photonic processing structures. Ever increasing requirements, driven by application developments, has lead to the rapid development of newer generations of such materials. As the ever increasing number of new materials is developed and used, there is a need to characterize the material behavior pre-and post exposure. In order to produce materials with a desired set of material properties one has to understand the photochemical processes present during recording. Although in most case emphasis is placed on studying the high spatial frequency response and the related limitations of such materials, the low spatial frequency response characteristics can also supply useful information regarding the processes taking place during grating formation. In this paper we present the experimental results obtained following a detailed examination of the low spatial frequency response of a photopolymer material in the case of exposure at different recording intensities. The time dependence of the diffraction efficiency of the grating must be then analyzed using the appropriate diffraction theory of phase gratings. Furthermore the results of examining the angular scans of the resulting grating diffraction efficiency are presented in order to specify the condition of the diffraction regime (e.g. thin, thick) for such low spatial frequency gratings.