Optical control offers a non-contact, high-precision and ultrafast route to manipulating quantum material properties1–5. Fractional Chern ferromagnetic states in moiré superlattices are a promising platform by which to pursue topological quantum computing6–10, but an effective optical control protocol has remained elusive. Here we demonstrate robust optical switching of integer and fractional Chern ferromagnets in twisted molybdenum ditelluride (MoTe2) bilayers using continuous-wave circularly polarized light. Highly efficient optical manipulation of spin orientations in the topological ferromagnet regime is realized at zero field using a pump light power as low as 28 nW µm−2. Using this optically induced transition, we also demonstrate magnetic bistate cycling and spatially resolved writing of ferromagnetic domain walls. This work establishes a reliable and efficient optical control scheme for moiré Chern ferromagnets, paving the way for dissipationless spintronics and quantized Chern junction devices.
