Patent ID: 7389022

Claim:
A photosensitive optical waveguide, comprising: a core; a cladding; a refractive index defining the core and the cladding; a slanted Bragg grating, SBG, with a given slant angle, θ, written into the optical waveguide; and a photosensitivity profile, W(r), such that: ⁢ k ⁡ ( θ ) = ∫ E core 2 ⁡ ( r ) · J 0 ⁡ ( 2 ⁢ π · r · sin ⁡ ( θ ) Λ ) · W ⁡ ( r ) ⁢ r · ⅆ r ∂ k ⁡ ( θ ) ∂ θ = k ⁡ ( θ ) = - ∫ E core 2 ⁡ ( r ) · J 1 ⁡ ( 2 ⁢ π · r · sin ⁡ ( θ ) Λ ) · W ⁡ ( r ) · 2 ⁢ π Λ ⁢ cos ⁡ ( θ ) · r 2 · ⅆ r where: r is the radius of the fiber θ is the slant angle of the grating, E core is the electric field of the fundamental mode, W(r) is the photosensitivity profile, Λ is the period of the Bragg grating, and J 0 is the 1st order Bessel function; and wherein k(θ) is a minimum and k′(θ) is a minimum for the given SBG slant angle, θ, and wherein W(r) has at least one photosensitive step, and a radial position of the photosensitive step being independent of a radial position of an index step between the core and the cladding of the waveguide.