Holographic films

A hologram can be done registering the interference pattern intensity between two beams, called a reference and an object beam, in a photosensitive material or holographic film as is shown in Fig. 18. 

Performed experiments have shown the fruitfulness of the devised approach to obtaining polymeric holographic film-type materials and the necessity to carry on the research and to improve parameters of film samples and procedure for their use with the view of creating an assortment of materials for hologram recording with wide spectrum of parameters. 

Figure 7-19 SEM photo of a holographic film made by aluminum metal deposition on a polymer film to be used for the production of holographic pigments. The average distance between the peaks of the structure is about 800 nm.

Bis-imidazole photoinitiators are well-suited to photopolymer holographic films because these photoinitiators are sensitive, can be stored indefinitely, can be sensitized to all visible wavelengths, and are readily compatible with binder systems. It was the coincident development of bis-imidazole photoinitiators which catalyzed the rapid growth of photopolymer films in DuPont, holographic films in particular. The ready sensitization of bis-inudazoles has been exploited in a wide variety of holographic photopolymer films sensitized to all major visible commercial lasers, including panchromatic sensitization for the production of fiill-color... 

Figure 13.1. Plot of refractive index modulation as a function of pattern spacing for several holographic film families.

Holograms can be replicated by simply bringing unexposed holographic film into contact with another hologram, then illuminating with a coherent laser beam at the reference beam angle. 

The introduction of commercial lasers coupled with newly-developed bis-imidazole photoinitiators in the 1960 s provided the key tools necessary for the successful development of holographic films. As discussed in this article, the applications which ensued have been diverse and continue to expand as needs multiply for efficient management of light. 

The development of these products resulted from an extensive study of HABIs as photooxidants in a proof paper product identified as DYLUX . This was the first evidence that HABIs could be commercially produced to give very stable coated film and paper producfs. The availability of HABIs then encouraged investigators to apply HABIs as photoinitiators in products such as silver photographic films, holographic films, waveguides, displays, resists, etc. 

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