A review of the theory of absorption on microscopic and macroscopic levels is given. This theory is then applied to the absorption of UV light by diazo-type positive photoresist during exposure. A formal treatment of the properties of polychromatic light is given. Using these analyses, the effects of polychromatic exposure of a photoresist are derived. Finally, experimental verification of Beer’s law and determination of the exposure quantum efficiency of a particular photoresist is given.
Chris A. Mack, "Absorption and exposure in positive photoresist," Appl. Opt. 27, 4913-4919 (1988)