The Investigation Of Ultraviolet Sensing For Micronano Fiber Coated Ag-doped ZnO Composite Graphene

Ultraviolet（UV）monitoring technology is widely used in many fields such as optoelectronic equipment,power system detection,optical fiber communication,combustion detection,geological detection and so on,which has a great impact on human production and life.Traditional photomultiplier tubes and silicon-based UV detectors have seriously limited the development of UV detection technology due to low quantum efficiency,large volume,high cost and strong interference.Therefore,the research of high performance optical fiber UV sensor is of great significance.In this paper,Ag doped ZnO composite graphene sensitive material is innovatively applied to optical fiber UV sensing technology.Compared with traditional UV detection methods,it has the advantages of electromagnetic interference resistance,corrosion resistance,simplicity,low cost,high stability and high detection efficiency.Based on optical carrier principle,multimode interference principle and evanescent field principle,the single mode-tapered multimode-single mode（STMS）and the single mode-double tapered multimode-single mode（SDTMS）sensing unit were designed.And based on first principles,the calculation of photoelectric properties of graphene,ZnO,different concentrate Ag doped ZnO,and different concentrate Ag doped ZnO composite graphene was presented.Theoretical analysis results show that Ag doping will affect the free carrier concentration of ZnO composite under UV light,and then the refractive index will change,resulting in a change in the intensity of the transmission spectrum of the sensor.In this study,ZnO composite graphene（0%）and different concentrate Ag doped ZnO composite graphene（1%～4%）were prepared by hydrothermal method and characterized by scanning electron microscopy（SEM）.The single mode-multimode-single mode（SMS）fiber structure was prepared by fiber fusion mechanism.SMS fiber structure was pulled into single cone and double cone by hydrogen and oxygen flame melting taping method,preparing STMS fiber structure and SDTMS fiber structure.Furthermore,different concentrations Ag doped ZnO composite graphene were closely combined with STMS fiber structure and SDTMS fiber structure respectively by the drop coating method,so as to obtain the UV sensing head for optical fiber sensing.In this paper,UV light irradiation intensities of 0 mW/cm~2,1.201 mW/cm~2,2.402 mW/cm~2,3.603 mW/cm~2,4.804 mW/cm~2,6.005 mW/cm~2,7.203 mW/cm~2,8.407 mW/cm~2were selected.The UV sensing characteristics of different concentrations Ag doped ZnO composite graphene were tested at room temperature and pressure.Experimental results show that compared with SDTMS fiber structure sensor without sensitive materials（uncoated/SDTMS）and STMS fiber structure sensor without sensitive materials（uncoated/STMS）,the UV absorption capacity for SDTMS fiber structure combined with different sensitive materials have different degrees of improvement.When Ag doping concentration is 4%,the highest sensitivity is-7.713×10^-5mW/mW·cm^-2,which is 2.85 times and 4.41 times of the sensitivity of uncoated/SDTMS and uncoated/STMS,respectively.It can be seen that both modified ZnO and double tapered multimode fiber structure are effective methods to improve the UV absorption characteristics of sensors.