The invention provides a photonic structure comprising a first region (3) formed from a material having a first refractive index; and an array of sub-regions (5) formed in the first region, each sub-region having a refractive index different to the first refractive index;wherein the array of sub-regions (5) can be defined by a plurality of rows and columns, wherein the position of each sub-region relative to adjacent sub-regions in each row and the properties of the sub-regions across each row are defined by parameters of a first type, and the position of each row relative to adjacent rows, and the properties of the sub-regions along each column are defined by parameters of a second type; and wherein at least one parameter of a first type and at least one parameter of the second type is varied systematically and independently across the array.The present invention gives rise to structures with photonic band structures that can be tailored to a particular application. A variation in the first type of parameter has a different effect to a variation in the second type of parameter. Variation in a first type of parameter alters the diffracting properties of each row in the stack of rows. Variation in a second type of parameter affects the reflective properties of the structure.According to another aspect of the invention, a method for manufacturing photonic structures is provided including a computer optimisation process in the design stage.