Patent ID: 6987591

Claim:
A volume hologram for modifying a characteristic of an input electromagnetic beam propagating in an input direction, said volume hologram comprising: a host material having a dielectric constant and a beam receiving region for receiving the input electromagnetic beam having a center wavelength λ when propagating in the volume hologram; a 3D lattice of inclusions spaced from one another incorporated in the beam receiving region of the host material, each said inclusion having a size and a center, wherein said inclusions are disposed with a spacing between centers of adjacent inclusions smaller than one third of the center wavelength for providing the volume hologram with an effective dielectric constant ∈ r different from the dielectric constant of the host material, and wherein said inclusions are arranged for inducing a pre-determined 3D pattern of dielectric perturbations in the beam receiving region of the host material, said pre-determined 3D pattern of dielectric perturbations having multiple regions of increasing dielectric constant alternating with regions of decreasing dielectric constant along a straight line crossing the beam receiving region, for modifying the input electromagnetic beam by diffraction thereupon.