Patent ID: 7248770

Claim:
A photonic structure comprising: a first region formed from a material having a first refractive index; and a two-dimensional array of sub-regions formed in the first region, the sub-regions arranged in rows along a first direction, each sub-region having a refractive index different to the first refractive index; wherein the position and properties of each sub-region in the first direction across the array are defined by parameters of a first type which are constant along a row, and the position and properties of each sub-region in a second direction across the array are defined by parameters of a second type, the second direction being different from the first direction; and wherein at least one parameter of the first type and at least one parameter of the second type vary monotonically in the second direction across the array, the at least one parameter of a first type varying independently of the at least one parameter of a second type.