Controllable fast-slow light conversion in cavity-magnon system with multiple yttrium iron garnets

Abstract

In order to simplify the conversion between slow light and fast light, we ameliorate the cavity-magnon coupling system and theoretically analyze the characteristics of group delay of the output field. The system under consideration consists of a microwave cavity and N yttrium iron garnets (YIGs), of which the quantity of YIG spheres is designed to be controlled by an external magnetic field. It is found, most importantly, that the conversion between fast and slow light can be realized by adjusting the number of YIG spheres that the external magnetic field acts on. Significantly, through adjusting the quantity N of magnons, the group delay can be stabilized at a required value even though the magnons are slightly detuned. Moreover, adjusting the quantity of YIG spheres can also alter the frequency corresponding to the fast-slow light effect, signifying that the conversion can be expanded to the frequency domain. Meanwhile, the cavity-magnon coupling strength required to generate the fast-slow light can be also effectively reduced by increasing the quantity of YIG spheres. Furthermore, we find that the cavity-magnon coupling strength and the cavity-field loss rate are complementary in terms of the group delay, which provides a feasible alternative for experimental design. The factors determining the slow-light limit have also been summarized based on their influence on the group delay. Our results have theoretical significance for the improvement of the generation and conversion of the fast-slow light, upgrading and innovating the information technology, especially in the field of all-optical networks.