| A magneto-optical device refers to a device that fabricated into a variety of optical information functions by utilizing the magneto-optical effect of the material.A magneto-optical modulator modulates a light beam by utilizing polarized light to undergo polarization plane rotation through a magneto-optical medium.There are also many types of magneto-optical modulators.The most commonly used are ferrimagnetic yttrium iron garnet(YIG)single crystals and their thin film magneto-optical modulators.In such a magneto-optic modulator,the magneto-optical film functional material is mostly replace the rare earth element into a metal-iron garnet YIG single by doping to form a crystalline internal substrate.The film formed by this growth mode exhibits a large limitation in the magneto-optical effect,the process is complicate and the magneto-optical signal intensity is controlled by the thickness of the material and they are proportional.In this paper,the bismuth dot array is grown on the surface of yttrium iron garnet single crystal by physical vapor deposition,and the surface magneto-optical Kerr effect of YIG film is enhanced by the interface effect.The bismuth(Bi)element is a semi-metal with a large atomic number and is widely used in magneto-optical materials due to its non-toxic and chemically stable feature.In the ferrimagnetic yttrium iron garnet type material,the bismuth element is directly doped into the YIG film to become a bulk magneto-optical material,which has a remarkable magneto-optical effect in the visible light/near-infrared range.The magneto-optical effect originated from the energy level splitting of iron caused by Bi,which was recognized as one of the promising magneto-optical materials.However,with the continuous development of two-dimensional integrated optoelectronic subsystems,we need to find a new magneto-optical material system with significant surface effects.Therefore,we grow Bi semi-metals on the surface of ferrimagnetic yttrium iron garnet to form a quantum dot array which has local plasma effect.It is desirable to enhance the surface magneto-optical effect of the YIG/Bi quantum dot system by the enhanced optical absorption properties of the Bi quantum dot array and the low-dimensional quantum anomalous Hall effect.Firstly,the ordered bismuth quantum dot array is fabricated on the surface of yttrium iron garnet by magnetron sputtering and transferring ultra-thin AAO template.The surface topography,magnetic properties and optical properties of YIG/Bi quantum dots system are studied.Since the ultra-thin AAO template is extremely thin and even nanometer-scale,this paper has done a detailed research on how to transfer ultra-thin AAO templates.How to peel off the template after the end of growth can not damage the quantum dot.This paper also explores and finds that tear-off method is the best choice.Subsequently,the magnetic and optical properties were characterized by ferromagnetic resonance test,Raman test,polar surface magneto-optical Kerr effect test.The results show that the surface magneto-optical Kerr effect of the film obtained in this way is obviously enhanced,and the maximum magneto-optical Kerr rotation angle is enhanced up to 900%.Secondly,we use the ultra-high vacuum molecular beam epitaxy(MBE)self-assembly method to produce a disordered bismuth quantum dot array on the surface of YIG single crystal thin-film.The surface morphology,interface microstructure,magnetic properties,optical properties and surface plasmon of YIG/Bi quantum dots system was investigated by SEM test,STEM test,Raman test,VNA-FMR test and EELS tests.The results show that the magneto-optical Kerr effect of the film surface obtained by this method also has a significant magneto-optical enhancement effect,and the magneto-optical Kerr rotation angle enhancement strength can reach 150%.Finally,we explain the surface magneto-optical Kerr effect enhancement from the perspective of surface plasmon resonance enhanced light absorption. |
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