Magneto-optical Spin Hall Effect And Its Sensing Properties

When a beam of light is reflected or refracted on the surface of the medium,the reflected or refracted light will have a very small lateral displacement in a direction perpendicular to the incident surface.This physical phenomenon different from geometrical optical prediction is called the spin Hall effect of light(SHEL).The reason for this phenomenon is that the left-handed and right-handed circularly polarized light have different propagation speeds in the medium,so this phenomenon is extremely sensitive to changes in the light transmission medium,which provides a theoretical basis for its application to the thickness or refractive index sensing of the medium.However,once the SHEL device is fabricated,its structural parameters are difficult to change,and the flexible control of the SHEL cannot be achieved,which greatly limits the practical application of the SHEL.In this paper,the magneto-optical Kerr effect(MOKE)is used to control the dielectric tensor of magneto-optical medium by external magnetic field,and then the SHEL is effectively controlled.We call it magneto-optical(MO)SHEL,and apply it to refractive index sensing.The amplification,regulation and sensing of MOSHEL excited by surface plasmon resonance(SPR)and thermo-optical(TO)effect are studied.The main work of this paper is as follows:(1)Combining the gold-silver bimetal SPR structure with Ce YIG(cerium doped yttrium iron garnet),a prism coupled MOSHEL structure based on the enhancement of SPR is designed,which realizes the regulation of SPR and SHEL by the magnetic field and the enhancement of SHEL by the excited SPR.Simulation calculations show that the regulation effect of the transverse magnetic field on SHEL at the resonance angle can reach 13?m.Through the analysis,it is concluded that the peak value of the regulation effect of magnetic field on SPR and SHEL almost appears at the same time,and the reason for the small difference of the peak position is analyzed.Compared with the single-layer metal structure,it is proved that the design structure has better SPR response.A MOSHEL refractive index sensor based on SPR enhancement is designed.(2)A liquid refractive index sensor based on MOSHEL is designed and fabricated,including a newly designed multilayer micro-nano structure magneto-optical sensor chip and a microfluidic channel for importing and exporting the liquid to be measured.The existing experimental light path of weak measurement is improved,the experimental error is reduced,and the imaging quality is improved.Based on the transverse magneto-optical Kerr effect,a larger MOSHEL and the refractive index sensitivity can be obtained in the wide refractive index interval and the incident angle range,with excellent flexibility and sensing performance.The MOSHEL sensing characteristics of sodium chloride solution at very low concentration are tested.As the concentration of the solution increased from0%to 2%,the MOSHEL value decreased from 190?m to 70?m.The measured refractive index sensitivity is as high as 2.9×10~4?m/RIU,which is in good agreement with the simulation results.(3)A novel MOSHEL based on TO modulation is proposed,and an experimental optical path is designed.In general,the influence of magnetic field on SHEL is mainly manifested as the change of magnetic field direction,while the intensity of magnetic field is not easy to control.Using the TO effect,we can adjust the refractive index of the medium,and then realize the real-time control of the MOSHEL.In order to realize this design,firstly,a TOSHEL experiment based on TO phase change material(vanadium dioxide)was designed and implemented.Through experiments,it is found that as the temperature of the TO material rises,its TOSHEL value also keeps increasing.Therefore,for the designed TO-MO SHEL,the introduction of TO effect will produce both intrinsic TOSHEL and MOSHEL due to the change of refractive index of the medium.Based on this conclusion,a steel sensor which can realize magnetic field and temperature sensing is designed.This paper focuses on the physical mechanism,calculation method and sensing application of MOSHEL,which plays a positive role in clarifying the mechanism of MOSHEL phenomenon and expanding its application.