Patent ID: 7292755

Claim:
An optical apparatus comprising a planar optical waveguide having at least two reflectors, the planar optical waveguide substantially confining in at least one transverse spatial dimension optical signals propagating therein, the at least two reflectors defining an optical resonator that supports at least one resonant optical cavity mode propagating substantially confined by the planar optical waveguide in the at least one transverse spatial dimension, wherein: at least one of the reflectors comprises a set of diffractive elements formed in or on the planar optical waveguide; the diffractive elements are arranged in or on the planar optical waveguide so that an optical signal in one of the resonant optical cavity modes is successively incident on the diffractive elements of the set; and the diffractive elements are collectively arranged in or on the planar optical waveguide so as to exhibit a positional variation in amplitude, optical separation, or spatial phase over some portion of the set, the diffractive elements of the set being collectively arranged so as to apply a transfer function to the optical signal successively incident on the diffractive elements of the set, the transfer function being determined at least in part by said positional variation in amplitude, optical separation, or spatial phase exhibited by the diffractive elements.