INDEX ultraviolet exposures

Figure i. Optical absoiption spectnim of thin film (0.7S/t) of MAI (17 %) polymer before and after exposure to intense short wavdength ultraviolet light, possible photochemical reaction mechanism, and observed refiracdve index changes in the film. 

In 2004, the ultraviolet (UV) index developed by the National Weather Service and the U.S. Environmental Protection Agency (EPA) in 1994, was replaced by the Global Solar UV Index. The new scale rates the level of UV exposure expected on a given day as measured at noon, although the actual UV rises and falls as the day progresses. The color-coded scale is shown in Table 17.6. 

Photopolymers behave in a fashion similar to photoresists, but instead of dissolving away during development, exposure of a photopolymer to light induces a chemical reaction in the material that changes its index of refraction or modulates its surface relief. Some photopolymers require no development processing, and others must be heated or exposed to ultraviolet light. 

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