Patent ID: 8005322

Claim:
A polarization-independent optical isolator comprising: a first branching/coupling device and a second branching/coupling device; a first waveguide and a second waveguide which are respectively connected to the first branching/coupling device and the second branching/coupling device; a non-reciprocal phase shifter which is provided so as to straddle on the first waveguide and the second waveguide, and which gives a prescribed phase difference to a forward propagating light and a backward propagating light respectively propagating in the first and second waveguides; a first mode converter provided on the first waveguide; and a second mode converter provided on the second waveguide; wherein the second mode converter is provided between the non-reciprocal phase shifter and the second branching/coupling device in a case where the first mode converter is provided between the first branching/coupling device and the non-reciprocal phase shifter, and the second mode converter is provided between the non-reciprocal phase shifter and the first branching/coupling device in a case where the first mode converter is provided between the second branching/coupling device and the non-reciprocal phase shifter.