Optical Fiber Sensors Based On Suspended Graphene

Optical fiber sensors have been widely used in various fields, including current sensor, gyroscope and hydrophone. At the same time, as an emerging opto-electrical material, graphene has been extensively studied. In this paper, we combine the advantages of the traditional optical fiber sensors and graphene, and fabricate a new optical fiber sensor based on suspended graphene.Details are as below:1. Design a set of fabrication process for the fiber sensor based on suspended graphene. In graphene sample preparation part, we use few-layers graphene grown by CVD method on copper foil, and put the copper foils into ferric chloride for corrosion. After corrosion is over, we use glass slides to transfer graphene into deionized water for cleaning. In the fiber sample preparation part, we use paraffin as a mask to fabricate the gold electrodes on both sides of optical fiber. In the graphene transfer part, we let the fiber end face down and put it gradually close to the surface of water. At the same time, graphene is bonded to the fiber end face due to the van der Waals force.2. Test the performance of the optical fiber current sensor. In the testing process, we couple the current to the gold electrodes of the fiber through two pieces of metal plate. And heat generated by the current causes the deformation of graphene, which makes the FP cavity length to change and the corresponding resonant wavelength to shift. By detecting the change of resonant wavelength, we can measure the current on the graphene membrane. The sensitivity of the current sensor is 0.22 nm/mA2, and the response time is about 0.3 s, which is much better than that of the traditional optical fiber current sensors based on thermal effect.3. Test the performance of the optical fiber magnetic field sensor. We use the method of pump-probe to measure the mechanical resonant frequency of graphene. When the current flows through the graphene membrane, it experiences Lorentz force in the magnetic field and the tension inside the graphene changes which leads the corresponding mechanical resonance frequency to shift. Through the detection of this shift, we can measure the magnitude of the magnetic field. In the experiment, the measured magnetic field sensitivity is 178 kHz/TIn short, we combine the advantages of graphene and optical fiber sensor, fabricate an optical fiber sensor based on the suspended graphene, and test the current sensing property and the magnetic field sensing property. We believe this new sensor can pave the way for the further development of optical fiber sensors.