Optical Isolator for TE Polarized Light Realized by Adhesive Bonding of Ce:YIG on Silicon-on-Insulator Waveguide Circuits

An optical isolator for transverse electric (TE) polarized light is demonstrated by adhesive bonding of a ferrimagnetic garnet die on top of a 380 nm thick silicon waveguide circuit. Polarization rotators are implemented in the arms of a nonreciprocal Mach-Zehnder interferometer to rotate the polarization to transverse magnetic in the nonreciprocal phase shifter regions. Calculation of the nonreciprocal phase shift (NRPS) as a function of bonding layer thickness experienced by the TM mode in the interferometer arms is presented, together with the simulation of the robustness of the polarization rotator. Experimentally, 32 dB isolation is measured at 1540.5 nm wavelength using a magnetic field transverse to the light propagation directions. This paves the way to the cointegration of laser diodes and optical isolators on a silicon photonics platform.