Optical properties of pure and doped polymers

This article deals with the optical properties of large bandgap polymers i. e. Polymers whose intrinsic absorption is in ultraviolet region of the spectrum. The article focuses on the optical properties of polymeric solids in the visible spectral range. In this range the above class of polymers can be considered as ‘transparent’. Many applications, such as applications for optical elements and for light fibers are based on the low optical losses of polymeric materials. The residual loss mechanisms, such as vibronic overtone absorptions and light scattering are discussed in some details. A comparison with inorganic glasses is performed, showing that materials like fused silica have lower losses than their organic counterparts. The second part of the article deals with the absorptive properties of polymers which are doped with dye molecules, absorbing in the visible range. The optical spectra of doped polymers are usually broad and structureless. It is shown how one can gain optical resolution by performing narrow-band photochemistry: Photochemical hole burning (PHB). The gain in optical resolution is on the order of 10³. It is shown that, based on this high resolution, one can study relaxation phenomena in polymers by the means of optical spectroscopy. Some simple relaxation phenomena are discussed together with some applications of narrow-band photochemistry in the field of high desity optical storage.