Effect of composition and two-step annealing on Ce-doped terbium iron garnets on Si

Cerium-doped terbium iron garnet (CeTbIG) thin films with varying compositions and thicknesses were deposited to determine a garnet formation region. Both grain size and Faraday rotation (FR) increased in this region as the Ce content increased until 20% of the dodecahedral sites were occupied by Ce. The high Ce content was achieved by lowering the Fe ratio with respect to the total rare earth content. Above 20% Ce, the Faraday rotation was relatively independent of composition at -830 o /cm, which is similar in magnitude to positive Faraday rotation garnets, e.g.: + 600 o /cm for undoped TbIG. Next, we found that a two-step annealing method, involving a 400°C pre-anneal followed by higher temperatures, effectively reduced the maximum temperature from 900°C to 800°C without decreasing the Faraday rotation. Finally, a Si-integrated interferometer was simulated using the stable (+) and (-) Faraday rotation materials developed in this work. The simulation identified a Si-integrated Mach Zehnder Interferometers (MZI) with “push/pull” nonreciprocal phase shifts (NRPS) of opposite signs that enable mm-scale with zero external magnetic field (field-free).