Silicon integrated Bi2TbFe5O12 thin films for O-band nonreciprocal photonic device applications

Silicon photonics for data communication requires key components in the O-band (1260 nm−1310 nm). However, very few studies report silicon integrated magneto-optical thin films operating at this wavelength range. In this study, we report a method to fabricate polycrystalline Bi₂Tb₁Fe₅O₁₂ thin films on silicon substrates for O-band nonreciprocal photonic device applications. The films are fabricated by magnetron sputtering at room temperature followed by rapid thermal annealing for crystallization. Pure garnet phase is stabilized by a Y₃Fe₅O₁₂ seed layer on silicon. The film deposited on silicon-on-insulator (SOI) waveguides showed saturation Faraday rotation of −3300 ± 183 deg/cm, propagation loss of 53.3 ± 0.3 dB/cm and a high figure of merit of 61.9 ± 3.8 deg/dB at 1310 nm wavelength, demonstrating promising potential for O-band integrated nonreciprocal photonic devices.