Uniform holographic films of acrylamide/polyvinyl alcohol photopolymer using an automatic film applicator based on doctor blade technique

Photopolymer films are preferred choice as hologram recording material due to their inherent advantages of reliability, affordability and ease of preparation. For fabrication of these films, different techniques are adopted such as dip coating, spin coating, drop casting etc. The spin coating, and dip coating techniques also find extensive utilization across numerous applications but they have limitations specifically in realizing uniform thickness of films over a larger area. The use of an automatic film applicator based on doctor blade technique is currently a highly advantageous method for use in pharmaceutical applications and offers significant benefits in terms of good uniformity with controlled thickness. In this study, holographic films are prepared using this automatic film applicator. Experimental evidence demonstrates the homogeneity and uniformity of the films fabricated. For a 7.15 mm scan length, the surface roughness of films employing the aforementioned method is 5.1 nm. For optimization purpose, photopolymer film composed of acrylamide (AA) and polyvinyl alcohol (PVA) is prepared. The films prepared with automatic film coater are also compared with the film prepared with other techniques such as drop coating and spin coating and it is observed that the photopolymer film realized by this method is capable of recording holographic gratings with 75 % diffraction efficiency, which is 53 % and 42 % in spin coated and drop casted films respectively for 90 μm thickness. The results indicate that the automatic film applicator based on doctor blade can potentially be implemented to create uniform, and better-quality photopolymer films for holographic applications while maintaining good repeatability with controlled thickness.