Patent ID: 6925232

Claim:
A thermo-optic phase shifting device for thermally changing the phase of light traveling therethrough comprising: an optical waveguiding structure comprising a first waveguiding core, a second waveguiding core and a cladding peripherally surrounding the first core and at least partially surrounding the second core; the first core having an index of refraction n 1 with a temperature dependence |dn 1 /dT|; the second core having a length less than the length of the first core and a pair of ends, the second core having an index of refraction n 2 with a temperature dependence |dn 2 /dT|, n 2 being greater than n 1 and |dn 2 /dT| being greater than |dn 1 /dT|; the second core optically coupled to the first core such that light traveling along the first core is coupled into the second core beginning at one of the ends and the light is coupled from the second core to the first core at the other of the ends; and a heater thermally coupled to the second core between the ends for thermally changing the index of refraction along the second core.