Sulfonation as a new technique of fabricating polymeric gradient-index lenses

Gradient-index (GRIN) lenses, whose refractive index varies continuously within the medium, have been useful as focusing elements, such as a connector and coupler of optical fibers, in optical communication systems. Glasses and polymers have been widely used in forming GRIN media, of which the polymers have milder processing condition and wider versatility in materials. Various copolymerization techniques have been used to form the gradient profiles of refractive index. Here, we report a new technique of fabricating GRIN medium in aromatic polymers using sulfonation method.