Monolithic integration of chalcogenide glass/iron garnet waveguides and resonators for on-chip nonreciprocal photonic devices

We report monolithic integration of chalcogenide glass(ChG)/iron garnet waveguides and racetrack resonators on silicon for on-chip nonreciprocal photonic devices applications. Using a two step growth strategy, we successfully integrated phase pure Bi0.8Y2.2Fe₅O₁₂ (Bi0.8YIG), Bi1.8Y1.2Fe₅O₁₂ (Bi1.8YIG) and Ce₁Y₂Fe₅O₁₂ (CeYIG) polycrystalline thin films on silicon with low fabrication thermal budgets. Strip-loaded ChG/Iron garnet waveguides and racetrack resonators were fabricated by thermal evaporation and lift off. The waveguide loss was systematically characterized by cutback and paperclip methods. For the first time, the optical transmission loss of polycrystalline Bi or Ce doped garnets were evaluated at communication wavelengths in waveguides. Polycrystalline CeYIG films show a saturation Faraday rotation of -830deg/cm and transmission loss of ~40dB/cm at 1550nm, which is promising for on-chip nonreciprocal photonic device applications. Such waveguide structures were successfully incorporated in GeS₂/Bi0.8YIG racetrack resonators which show well defined resonance spectrum at near infrared wavelength. The nonreciprocal phase shift (NRPS) and device figure of merit of the ChG/Garnet waveguides were simulated by numerical methods. Possible improvements and applications of such devices for integrated optical isolator applications are analyzed and discussed.