Detecting phase-resolved magnetization dynamics by magneto-optic effects at 1550-nm wavelength

We demonstrate the detection of phase-resolved magnetization dynamics with combinatorial magneto-optic Kerr and Faraday effects. The method uses a continuous-wave laser that is amplitude-modulated at the spin dynamic frequencies and thus allows for coherent tracking of the spin dynamics, akin a “lock-in”-type measurement. In particular, our method, using a single 1550 nm wavelength, probes simultaneously the ferromagnetic (FM) resonance of Y3Fe5O12 (YIG) and Permalloy (Py = Ni80Fe20) in a YIG-Py heterostructure. The fiber-based magneto-optic components also have the advantage of being made into a compact, tabletop or even portable system with yet robust measurement performances. We believe that our method will be found useful in studying hybrid quantum magnonic systems and/or investigating phase-resolved spin dynamics in nanomagnet structures involving both FM insulators and metals.