Temporal magnetized ferrite slabs for nonreciprocal wave propagation and arbitrary Faraday rotations

Abstract

Nonreciprocity plays a crucial role in the realization of optical diodes, isolators, and circulators. Conventional nonreciprocal devices are typically fabricated using magneto-optical materials, which require strong external magnetic fields and patterned structures. Recently, nonreciprocity and Faraday polarization rotation have been demonstrated in a temporal magnetized plasma slab by abruptly changing its material parameters. In this paper, we develop a transfer matrix method to analyze the propagation of electromagnetic waves through a multilayer temporal structure composed of successive magnetized ferrite slabs. In the proposed structure, the spatially homogeneous medium abruptly transitions from free space to a magnetized ferrite and then back to free space after a defined time interval. By introducing a figure of merit, we determine the optimal values for the external magnetic field strength and the temporal thickness of the slab such that the structure functions as a 45° Faraday rotator. Furthermore, nonreciprocity in polarization conversion is demonstrated for this temporal structure. This confirms the potential of the proposed temporal structure to realize a Faraday isolator in the radio frequency region without the need for strong magnetic fields, spatial boundaries, patterned structures, or electromagnetic field confinement within an optical cavity. Additionally, we show that arbitrary polarization rotation of a linearly polarized incident wave can be achieved by appropriately selecting the external magnetic field and temporal width of the ferrite slab. Our results suggest that temporal structures based on ferrite materials hold promise for applications in wave engineering and the design of nonreciprocal devices.