Patent ID: 7499612

Claim:
A method, comprising: forming a planar optical waveguide, the planar optical waveguide substantially confining in one transverse spatial dimension an optical signal propagating in two other spatial dimensions therein; and forming a set of diffractive elements in the planar optical waveguide, wherein: the planar optical waveguide is arranged so as to support multiple optical transverse modes in the confined transverse dimension; each diffractive element set is arranged so as to route, between a corresponding input optical port and a corresponding output optical port, a corresponding diffracted portion of the optical signal propagating in the planar waveguide that is diffracted by the diffractive element set; the diffractive elements are arranged so that the optical signal is successively incident on the diffractive elements; and the diffractive elements and the planar optical waveguide are arranged so that the corresponding diffracted portion of the optical signal reaches the corresponding output optical port as a superposition of multiple optical transverse modes supported by the planar optical waveguide.