Fiber Optic Magnetoelectric Sensors Based On Graphene And Graphene-based Hybrid Structures

Optical fiber is an optical waveguide based on the principle of total reflection.Due to its light weight,anti-electromagnetic interference,anti-corrosion,small size,capability of remote operation and multiplexing,it is very suitable for the research and application of sensing.The fiber optic Fabry-Perot cavity sensor realizes sensing by external force acting on the reflection film to change the cavity length.It has high sensitivity,compact structure and good stability,and has been widely used in the fields of displacement and pressure sensing.Graphene is a honeycomb two-dimensional material composed of carbon atoms.Due to its large specific surface area,ultra-thin thickness,high young's modulus,high stiffness,low density,graphene has become an excellent micro-nano functional material,which has been applied in biomedical,energy,chemical,electronics,sensing and other fields.In this paper,the fiber Fabry-Perot cavity structure is combined with graphene to realize the detection of magnetic field and current respectively based on static interference and dynamic graphene nanoelectromechanical system.1.Fiber Fabry-Perot cavity structure is prepared by welding a small piece of capillary glass tube on the end face of an optical fiber and then transferring the graphene film.The coating technology is used to control the thickness and quality of the gold film plated on the end faces and sides of the fiber.The gold film can be used both as a conductive material and to enhance the force between graphene and the substrate to improve the sensing recovery of the device.With the help of a high-precision three-dimensional adjustment table and a tungsten probe,the micro-machining modification of the gold film is realized.2.Based on the principle of static interference,the detection of magnetic field intensity is realized.The prepared fiber Fabry-Perot cavity structure is further plated with gold film,the composite film formed by the gold film and graphene film forms the second reflective surface of the cavity.And then the gold film is modified to prepare the electrodes.When the current flows through the graphene-gold composite film,the Ampere force generated by the magnetic field causes it to deform,and the length of the Fabry-Perot cavity will change,thus changing the interference light intensity and sensing the magnetic field intensity.The device has excellent linear response,good recovery and stability,but the detection limit needs to be improved3.Graphene nanoelectromechanical system is to study the electromechanical properties of graphene with micro-nano size,such as the response of its resonance frequency to force,electric field and temperature,and the energy dissipation behavior under different environments.Based on the sensitivity of the resonant frequency of graphene to force,galvanometer and magnetometer are prepared respectively.The prepared fiber Fabry-Perot cavity structure is coated by the developed UV mask coating technology,and the electrodes are modified on the sides of the fiber.When the current flows through the suspended graphene,the thermal effect produced changes the internal stress of the graphene,which in turn changes its resonance frequency,thus realizing the sensing of the current.The sensitivity of the device is very high,but the recovery needs to be improved.If the electrodes are not modified,the effect of the gold-plated film is only to enhance the force between the graphene and the substrate.And then transfer the superparamagnetic nanoparticles to the surface of the suspended graphene,the magnetometer is prepared.When a gradient magnetic field is applied to the magnetic nanoparticles,the resulting force changes the resonance frequency of the graphene,enabling sensing of the product of magnetic field gradient and magnetic field strength.The response linearity and recovery of the device are excellent.When used together with miniature magnetic field intensity sensor,it has great potential in magnetic field gradient sensing.