Patent ID: 6943932

Claim:
A waveguide optical isolator for providing low attenuation for a light propagating in a forward direction and high attenuation for a light propagating in a backward direction, said optical system comprising: an input optical waveguide section; a first and second optical waveguide arms coupled to said input optical waveguide section for each receiving approximately an equal portion of an input light wave propagating in a forward direction and respectively propagating each approximately equal portion as first and second light waves in the forward direction in said first and second optical waveguide arms, and for providing to said input optical waveguide section a combined first and a second light wave propagating in a backward direction from said first and second optical waveguide arms, respectively, said first and second optical waveguide arms being fabricated at least in part with a material that provides a transverse magneto-optical non-reciprocal phase shift, said first optical waveguide arm being longer than the second optical waveguide arm by a length that results in a 90 degree reciprocal phase difference of said first light wave propagating through said first optical waveguide arm relative to said second light wave propagating through said second optical waveguide arm; first and second magnets applying respective transverse magnetic fields to said first and second optical waveguide arms, said transverse magnetic fields, being of the same magnitude but of opposite polarity so as to cause a non-reciprocal +45 degree phase shift for said first light wave propagating in the forward direction in said first optical waveguide arm and a −45 degree non-reciprocal phase shift for said second light wave propagating in the forward direction in said second optical waveguide arm, said magnetic fields causing a non-reciprocal −45 degree phase shift for said first light wave propagating in the backward direction in said first optical waveguide arm and a +45 degree non-reciprocal phase shift for said second light wave propagating in the backward direction in said second optical waveguide arm; and an output optical waveguide section coupled to said first and second optical waveguide arms for receiving in combination said first and second light wave propagating in a forward direction from said first and second optical waveguide arms, and for providing approximately an equal portion of a feedback light wave propagating in the backward direction in the output optical waveguide section to each of said first and second optical waveguide arms for respectively propagating therein as said first and second light waves.