Abstract
We theoretically and experimentally study the cavity modes in a gyromagnetic photonic crystal (GPC). Because the permeability of gyromagnetic material relies on the dc magnetic field exerted upon it, the band gap of the GPC is supposed to be tunable. Based on this, it is expected that the cavity mode in the GPC is also tunable under the variation of dc magnetic fields. The relation between the frequency of the cavity mode and exerted dc magnetic field is theoretically investigated. Furthermore, we measure the frequency variation of the cavity mode in the GPC and demonstrate the tunable property of GPC cavity.