Patent ID: 7233729

Claim:
A method for guiding electromagnetic radiation, comprising: providing a photonic crystal made of a bulk material having a first refractive index, said photonic crystal having, at least in a portion thereof, a periodic array of regions with a second refractive index different from the first refractive index, said regions having predetermined dimensions and said array having a predetermined period; and feeding to said region of said photonic crystal an electromagnetic radiation having a wavelength in the fundamental photonic band of said photonic crystal, wherein said wavelength, the difference between said first and second refractive indices, the dimensions of said regions and the period of said array are so related that, starting from an isotropic distribution of wave vectors, having group velocity vectors which correspond to said wave vectors, of said electromagnetic radiation within a first angular range that is twice the angular extension of a first irreducible Brillouin zone of said photonic crystal, the group velocity vectors corresponding to said wave vectors being rearranged as concerns direction and module so that at least 50% of said group velocity vectors are directed within a second angular range that is about one-third of said first angular range and a width at half-maximum of the distribution of the modules of said group velocity vectors is lower than about two-thirds of said second angular range.