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Recording of holographic volume di raction gratings in Du Pont's photopolymer HRS-150 is studied theoretically and experimentally. Particular attention is paid to the dynamics of the recording process. The temporal evolution of holographic gratings is monitored for a range of illumination intensities in two ways: (i) by means of a multiple-exposure approach when intensity pro®les of recording beams are uniform, many holographic exposures are necessary and each exposure is carried out for a particular value of the total illumination intensity; (ii) by means of a single-exposure approach when intensity pro®les of recording beams are strongly Gaussian and a volume grating with spatially distributed di raction e ciency arises, depending on a local (average) value of the total illumination intensity. The second approach proves to be a useful tool providing us very quickly with qualitative information about the dynamics of the recording process while the ®rst one, which is much more time-consuming, is more reliable for quantitative evaluations. The grating evolution is analysed theoretically by means of the well known photopolymerization-di usion model. Discrepancies are found between the model and experimental results for low illumination intensities while qualitative agreement is found for higher intensities. For a given grating period, the discrepancies are interpreted in terms of insu cient change of the refractive index due to photopolymerization for low illumination intensities.

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A single collimating transmission off-axis blazed surface-relief holographic diffractive element that corrects the ellipticity and the astigmatism of a diode-laser beam was designed. The procedure was applied to a hypothetical laser operating at a wavelength of 633 nm that possesses extremely large astigmatism and relatively small ellipticity together with small diverging angles of the laser beam. The element was recorded with only homocentric diverging beams that had pure spherical wave fronts. Because of the off-axis nature of the element, the aberration of asymmetry had to be corrected. The element was tested in a reciprocal way when the incident wave was a collimated He-Ne laser beam. A diffraction-limited beam was obtained that was as large as approximately half of the designed aperture.

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