Magnetically tunable ferrite-loaded waveguide isolator based on magnetic photonic crystals

Abstract

In this paper, a new ferrite-loaded waveguide isolator with frequency tunable is presented. Two pairs of ferrite cylinders are placed near sidewall in the waveguide. The magnetization of two pairs of ferrite rods are in opposite directions. One-way electromagnetic edge states has been demonstrated and observed experimentally in microwave regime. Such one-way propagation characteristics are usually realized by applying an external bias magnetic field perpendicular to magnetic photonic crystals lattice to break time-reversal symmetry. Although magnetic photonic crystals one-way electromagnetic edge states exhibit excellent ability to inhibit backward transmission, but the forward transmission loss is high. In order to reduce the loss, we propose to use two pairs of ferrite rods instead of magnetic photonic crystals lattice. Magnetic surface plasmon resonance is excited in the vicinity of both two pairs of ferrite rods in the working frequency. The numerical simulations were performed using the full-wave electromagnetic simulator CST Microwave Studio. The simulation results show the difference between forward and backward transmission is approximately 15 dB with insertion loss less than 2 dB. Moreover, the working frequency of waveguide isolator shows a magnetically tunable behavior. By adjusting the bias magnetic field, magnetic surface plasmon resonance frequency drift regularly. Therefore, the working frequency is tunable within a certain range without changing the size of waveguide. This approach opens a way for designing tunable waveguide isolator. Flexible magnetic tunability has greater potential for the tunable microwave devices.