Characteristics of Y3Fe5O12 ceramic at mid-infrared wavelengths and its Faraday isolator application

Compared to the commonly used 1 μm wavelength Faraday isolators (FIs), the performance of existing mid-infrared FIs remains unsatisfactory due to the lack of suitable magneto-optic (MO) candidate materials. In this study, we described a novel mid-infrared FI based on Y₃Fe₅O₁₂ (YIG) MO ceramics for the first time. The Faraday effects of YIG ceramics synthesized by hot-press sintering were tested and compared with those of commercial YIG single crystals and Bi-doped iron garnet (BIG) films. Faraday rotation angles of 114 deg/cm at 2.1 µm and 60 deg/cm at 3.8 µm have been demonstrated in YIG ceramics. The YIG ceramic-based FI exhibited an extinction ratio of 25.26 dB and an insertion loss of 1.01 dB at 2.1 µm, while the YIG ceramic-based Faraday rotator showed an extinction ratio of 28.30 dB and an insertion loss of 1.17 dB at 3.8 µm. Under high repetition rate pulsed laser radiation, surface damage was observed for both the YIG ceramic and the YIG crystal at similar laser power densities. Given its size scalability, further improvement in the optical quality of YIG ceramic is expected to provide a superior approach for realizing high power mid-infrared FIs.