The University of British Columbia

A novel passive polarization converter is presented using the elasto-optic effect in a ridge waveguide. A compressively stressed Si3N4 layer is deposited onto one side of the waveguide while a tensile layer is deposited on the opposing side. The average stress of the tensile and compressive layers is used to cancel the modal transverse-electric-transverse-magnetic (TE-TM) birefringence of the ridge waveguide. The difference in the tensile and compressive stresses induces birefringence with principal axes rotated 45 degrees from the TE-TM orientations. The method is demonstrated on an AlGaAs-GaAs waveguide at 1550 run. We measure the orientation of the axes to be 46 degrees +/- 1 degrees, demonstrating that complete mode conversion can be obtained without using periodic phase matching. Complete conversion is obtained in 1.16 mm with a waveguide loss of 0.1 dB/cm. Stability over temperature is also demonstrated.