A method of fabricating a gyrotropic device (e.g., an optical isolator) includes: providing a substrate comprising a waveguide layer and forming an optical isolator active layer on the waveguide layer of the substrate. Forming the optical isolator active layer includes, for a specified composition of the optical isolator active layer, deriving at least one sputtering process parameter, performing sputtering of a plurality of targets according to the at least one sputtering process parameter to deposit the optical isolator active layer on the waveguide layer of the substrate, measuring an initial value of a bias voltage at a first target of the plurality of targets; and throughout deposition of the optical isolator active layer, maintaining the bias voltage at the initial value to within a predetermined threshold of the initial value.