TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The second component has a refractive index n2 greater or smaller than n1. The second component is: a dielectric material comprising polymeric materials that are poly(methyl methacrylate), polycarbonate, polystyrene, cellulose acetate or poly(vinyl carbazole) and inorganic materials comprising silica, titania, hafnia, silicon or germanium; air; or metal or a dielectric material containing a metal. The fluorinated polymer has a bulk refractive index of 1.25-1.35. The fluorinated polymers comprising alicyclic structures in the polymer main chain are those comprising recurring units derived from at least one fluorinated monomer that is fluorodioxoles of formula (I), the fluorodioxolanes of formula (II) or cyclopolymerizable monomers of formula (CR7R8=CR9OCR10R11(CR12R13)a(O)bCR14=CR15R16) (III). The functional fluoropolyether compound is of formula (T1-j1-R1f-j2-T2) (IV).R1-R6 = -F, 1-6C fluoroalkyl optionally comprising at least one O, 1-6C fluoroalkoxy, optionally comprising at least O;R7-R16 = -F or 1-3C fluoroalkyl;a, b = 0 or 1, preferably R1, R3, R4 is -F and R2 is -OCF3 or R1, R2 is -F and R3, R4 is -CF3;R1f = fluoropolyoxyalkylene chain comprising recurring units of formula (-(CF2)k-CFZ1-O-);k = 0-3;Z1 = F or 1-5C perfluoroalkyl optionally comprising at least one O;j1, j2 = bond or divalent bridging group;T1, T2 = -O-CO-CR1h=CH2, -O-CO-NH-CO-CR1h=CH2 or -O-CO-R1a-CR1h=CH2;R1h = H or 1-6C alkyl;R1a = -NH-R1b-O-CO, -NH-R1b-NHCOO-R1b-OCO-; andR1b = divalent group that is 1-10C aliphatic group, 5-14C cycloaliphatic, 6-14C aromatic or alkylaromatic group.Provided that b is 0 when a is 1. Preferred Method: The elastomers comprising fluoropolyether chains are obtained by the UV-curing of compositions comprising: at least one functional fluoropolyether compound comprising a fluoropolyoxyalkylene chain (R1f) and having at least two unsaturated moieties; and at least one photoinitiator. The method further comprises removing monodisperse spheres, when the monodisperse spheres are made of the second component and curing the precursor by UV radiation to obtain an elastomer comprising fluoropolyether chains filling the interstices between the monodisperse spheres. The two- or three-dimensional periodic or crystalline structure is infiltrated with a precursor of the first dielectric component, where the precursor comprises at least one functional fluoropolyether compound comprising a fluoropolyoxyalkylene chain and at least two unsaturated moieties and at least one photoinitiator. EXAMPLE - Interstices in a three-dimensional crystalline structure comprising polystyrene monodisperse spheres (diameter of 300 nm) were prepared and infiltrated by dip coating using a 10 wt.% solution of HYFLON AD60 (RTM: Tetrafluoroethylene/2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole copolymer). The solvent was removed by evaporation at room temperature to obtain photonic crystal.