Time-Resolved Brillouin Light Scattering measurement of a 1D YIG magnonic crystal

Magnonic crystals are created by introducing a periodic modulation of the material properties that leads to the formation of bands of allowed frequencies where spin waves can pass through the crystal and band gaps where propagation is suppressed. Analogous to photonic crystals in optical devices, magnonic crystals show promise for signal processing and logic applications. Here we report time-resolve Brillouin light scattering (TR-BLS) measurements of a 1D yttrium iron garnet (YIG) magnonic crystal. We have used TR-BLS in the surface wave geometry to observe 200-ns long spin wave pulses with frequencies of 4 to 5 GHz propagating through the magnonic crystal. Microwave measurements confirm that periodic grooves etched into the YIG film create band gaps that suppress the transmission of spin waves by >15 dB, and these band gaps are directly observed in the TR-BLS measurements. The TR-BLS measurements provide direct insight into the temporal and spatial evolution of the propagating spin wave packet as it travels through the magnonic crystal, and the differences in the pulse propagation at frequencies within the pass band and within the band gaps will be discussed.