An application of reflective holographic gratings for measurement of cylindrical curvature

This paper presented an application of reflective holographic gratings for the measurement of cylindrical curvature. The surface of the fabricated holographic grating was coated with gold by the sputtering method, where it became a reflective holographic grating. The grating was attached to the surface of various radius cylindrical objects. The diffraction pattern produced by the bent grating with different radius was observed by illuminating a laser beam normal to the grating surface. The gratings constant were calculated from the observed diffraction pattern. The relationship between the grating constants and the radius of cylindrical objects was obtained. The grating constant and the reciprocal of the radius of cylindrical objects was a linear relationship, with the least R-square between 0.85-0.97. Moreover, the y-intercept of the relationship between the grating constants and the reciprocal radius was consistent with the grating constant of the non-bended grating. As the radius of the grating approach is infinite, the reciprocal of the radius approaches zero, which is a non-bend grating. We can apply this method to measure the radius of cylindrical objects.

Holographic Grating Enhancement of TI/PMMA Polymers in the Dark Diffusion Process

The dark diffusion enhancement process (DDEP) caused by photopolymerization during the pre-exposure of TI/PMMA (titanocene dispersed methyl methacrylate matrix) polymers was theoretically analyzed and experimentally investigated, revealing the holographic grating enhancement of TI/PMMA polymers in the post-exposure process without additional operations. The diffusion of photo-initiators and photoproducts dominated the grating enhancement process after exposure. We adopted two pre-exposure methods, long-time (second level) and short-time (millisecond level) laser exposure, at 532 nm, to investigate the DDEP during the post-exposure process. A five-fold enhancement in grating strength was achieved in consecutive long-time pre-exposures, while a two-fold grating development was examined after short-time exposure. Additionally, the exposure durations and repetition rates influenced the grating increment of the DDEP. This study provided a basis for the feasibility of holographic application in TI/PMMA photopolymers via the dark diffusion effect.

Энергетический обмен при встречном двухволновом взаимодействии в кристалле Bi-=SUB=-12-=/SUB=-GeO-=SUB=-20-=/SUB=- среза (001)

The regularities of energy transfer between two linearly polarized light waves as their contra-directional mixing on a volume reflection holographic grating formed in a photorefractive Bi12GeO20 crystal of the (001)-cut are analyzed. The values of the crystal thickness and the azimuths of the linear polarization of the light waves, at which the amplification of the object wave is achieved, are determined. The change in the direction of energy transfer to the opposite, depending on the thickness of the crystal, has been experimentally demonstrated.