Magnon-induced Transparency And Fast-slow Light In A Cavity-magnon System

Multiple window electromagnetically induced transparency has been extensively studied as an effective method to realize multiband quantum memory.Subsequently,the multiple window electromagnetically induced transparency in many physical models has been realized.But a practical question is whether this result can be achieved at higher temperatures,such as a multiband quantum memory at room temperature.In recent years,remarkable developments have been achieved in the strong coupling of the quanta of spin waves(magnons)to the cavity photons.Since the spin ensembles are robust against temperature,the magnetically induced transparency has been successfully demonstrated at room temperature.These results demonstrate the promising value of the cavity-magnon system for practical quantum memories.In this paper,the output field optical properties and the group delay of a strong probe field or a weak probe field are explored separately in a cavity-magnon system composed of multiple YIG spheres and a microwave cavity.When the amplitude of the probe field is relatively large,one finds that the number of interference windows for the output field is equal to the number of YIG spheres with different magnon frequencies.The number of YIG spheres with the same frequencies and dissipation rate of the cavity field can affect the height and width of the interference window.For the case of the two YIG spheres,we discuss the manipulation of the interference window in detail.It can be found that: by tuning the relative phase of the magnon pumping and cavity-probe tones,the pump-probe amplitude ratio and the magnon frequency can respectively control the interference window type(transparent,amplification and absorption window),the numerical value of the transmission spectrum and the position of the interference window.When destructive interference occurs,the magnetically induced transparency,absorption and amplification conversion can be achieved only by changing the pump-probe amplitude ratio.This conclusion is still valid for the system containing multiple YIG spheres,which is significative to the study of”optical frequency comb”.For the case of three YIG spheres,we investigate the fast-slow light phenomenon of the output field.The fast-slow light phenomenon occurs when the interference window emerges,so the location depicted the transmission spectrum of the fast-slow light phenomenon can be regulated by changing the magnon frequency;Changing the relative phase of the magnon pumping and cavity-probe tones brings a conversion between fast and slow light;When destructive interference occurs,the conversion of fast and slow light can also be achieved only by changing the pump-probe amplitude ratio;With certain parameter values,we increased the group delay to an order of magnitude of 0.1s.When the probe field amplitude is much smaller than the driving field amplitude,the vibrations of the YIG spheres and the magnon-phonon interactions caused by the magnetostrictive force must be considered.By calculating it numerically,we find that the number of transparent windows in the absorption spectrum of the probe field is equal to twice the number of YIG spheres with different effective magnon-phonon coupling strengths;The number of YIG spheres of the same effective magnon-phonon coupling strength is only related to the width and depth of the transparent window.For the case of the two YIG spheres,we explore the relationship of the group delay to the effective magnon-phonon coupling strength of the YIG sphere.The conversion of fast-slow light is achieved by changing the effective magnon-phonon coupling strength of the YIG sphere.The results obtained here may be helpful for the study of multiband quantum memory and coherent state storage.