METHOD FOR DESIGNING A DIFFRACTION GRATING STRUCTURE AND A DIFFRACTION GRATING STRUCTURE

摘要

According to the present invention, the method for designing a diffraction grating structure (1), the grating period (d) of the structure comprising at least two grating lines each consisting of a pair of adjacent pillars (2) and grooves (3), comprises the steps of—determining desired diffraction efficiencies η_d of the diffraction orders, and—dimensioning the pillars (2) and grooves (3) so that when calculating for each pillar, on the basis of the effective refractive index n_eff for the fundamental wave mode propagating along that pillar, the phase shift Φ experienced by light propagated through the grating structure, the differences in the calculated phase shifts between adjacent pillars corresponds to the phase profile Φ_r required by the desired diffraction efficiencies.