Three dimensional diffraction grating and crystal filter

A rigid three dimensional diffraction grating is provided in the form of an ABA block copolymer that forms domains. The A domain of the block copolymer is preferably polystyrene and the B domain of the copolymer is preferably a diene such as polybutadiene or polyisoprene. The molecular weight of the diene can be synthetically controlled to regulate the interelement spacing of the polystyrene domains and control the diffraction obtained from the grating.