As an example of a suitable matrix material one can use various optically transparent materials, for example polycarbonates, polystyrenes, polyolifines, polyacrylates such as polymethylmethacrylates, polyvinyl derivatives, polyesther derivatives, polyvinyl chloride; cellulose derivatives such as cellulose acetate, polyurethanes, polyethylene terephthalate; silicone resins such as LSR (liquid silic