Broadband and switchable fast–slow light in the YIG-microstrip cavity system

We experimentally study the fast–slow light induced by multiple-path microwave interference in the yttrium iron garnet (YIG)-microstrip cavity system. The destructive interference between two types of paths, the direct path through the traveling wave and the indirect paths through the magnon and the resonator, leads to a nearly blocking of microwave transmission when the magnon mode resonates at a particular frequency. This phenomenon is accompanied by a dramatic evolution to the phase of microwave transmission, which strongly adjusts the group velocity of light. Tuning the magnon mode crossing the particular frequency by controlling the external magnetic field, the polarity of phase evolution will be reversed, which presents as a switch between phase delay (slow-light) and phase advance (fast-light). And we experimentally achieve the broadband fast–slow light by tuning the external damping of the magnon. Furthermore, we predict the broadband fast–slow light in different physical parameters. Our results demonstrate that the destructive interference in the YIG-microstrip cavity system is a way to manipulate fast–slow light, which has a great significance in quantum information processing and storage.