High gyrotropy photonic isolators directly on substrate

A method of fabricating a gyrotropic device, the method comprising:

• providing a substrate;
• and
• forming an optical isolator active layer on the substrate, wherein forming the optical isolator active layer comprises:
• for a specified composition of the optical isolator active layer, deriving at least one sputtering process parameter;
• performing radio-frequency sputtering of at least one target according to the at least one sputtering process parameter to deposit the optical isolator active layer on the substrate;
• measuring a first value of a bias voltage at a first target of the at least one target;
• during deposition of the optical isolator active layer, monitoring the bias voltage;
• and
• in response to the monitored bias voltage, adjusting a sputtering process parameter distinct from the bias voltage, wherein the adjustment maintains the bias voltage within a target range that includes the first value.