A dye loaded zeolite composite material comprises a plurality of zeolite crystals each having a plurality of straight through uniform channels extending between the proximal face and the distal face and having a channel axis parallel to and a channel width transverse to a longitudinal crystal axis A. Each channel contains a substantially linear arrangement of dye molecules comprising first and second dye molecules having an elongated shape with a longitudinal extension exceeding said channel width and a lateral extension not exceeding said channel width. Each dye molecule consists of a chromophore moiety arranged between a pair of terminal moieties, wherein: the chromophore moieties of the first and second dye molecules are substantially identical, the terminal moieties of the first dye molecules have a lateral extension larger than half of the channel width, the terminal moieties of the second dye molecules have a lateral extension smaller than half of the channel width, the linear arrangement of dye molecules comprises at least one pair of second dye molecules adjacent each other.
