Application Of Femtosecond Laser Processing Technology In Optical Fiber Sensor And Micro-hole Machining

Optical fiber micro-sensor with high sensitivity,good reliability,anti-electromagnetic interference,easy networking,intelligent,etc.,has gotten people's attention.Micro sensors can accurately measure various physical quantities such as temperature,refractive index and strain in real time,and have great application background in medical diagnosis,food quality identification and environmental monitoring.It is very important to develop the optical fiber micro sensor with reliable and durable structure and excellent function in the field of sensor technology development and technological progress.Femtosecond lasers can be fabricated as a single-step(without additional assembly process)3D micro/nano structure due to their ultra-fast and super-powerful(?10¹³W/cm²)pulses.Femtosecond lasers have recently demonstrated unique advantages in fiber-optic micro-sensor processing.Combining the advantages of femtosecond laser micro-nano processing and optical fiber sensing technology,this dissertation mainly studies all-fiber micro-nano Fabry-Perot interferometer optical fiber sensor based on femtosecond laser processing.In order to extend the universality of femtosecond laser processing technology,we also studied the application of femtosecond laser micro-nano machining technology in metal material drilling,the main innovations of this thesis are as follows:A Fabry-Perot interference-based all-fiber micro-nano pressure sensor is proposed.The sensor uses the femtosecond laser to process micropores and membrane structures on the pure quartz photonic crystal fiber end face,and the microporous membrane is sealed with a quartz membrane Micro-cavity,the external pressure can change the shape of the diaphragm,making the cavity length of the law Perot cavity changes,the interference spectrum changes with pressure drift.Sensing head size is less than 100?m,in 1MPa pressure range,the pressure sensitivity of measurement up to 282nm/MPa.At the same time the sensor response speed,and can withstand high temperatures above 800 degrees.A Fabry-Perot interference-based all-fiber micro-nano pressure and temperature two-parameter sensor is proposed.The sensor uses quartz capillary tube to make extrinsic Fabry-Perot hollow microcavity and femtosecond laser at the microcavity end face.The diaphragm is used as a pressure sensitive element to measure the pressure change.A femtosecond laser is used to process the micropore structure on the end face of the optical fiber.The fused single-mode optical fiber forms an intrinsic Fabry-Perot solid microcavity,which measures the temperature change as a temperature sensitive element.The spectra of the three-beam interference are demodulated,and the cavity lengths of the two cavities are demodulated under different pressure and temperature conditions respectively.In the range of 800?,the sensitivity of the length of the solid cavity with temperature change is 7.3nm/?,the length of the hollow cavity changes little with the temperature.The sensitivity of the length of the hollow cavity with pressure change is 225nm,the sensitivity is 3.3nm/k Pa,the corresponding solid cavity is 0.4 nm/k Pa.According to the two different temperature and pressure sensitivity of the cavity can simultaneously demodulate the temperature and pressure,to achieve two-parameter measurement.The use of femtosecond laser and space shaping technology in a variety of metal materials were perforated research,selected iron,stainless steel,aluminum and molybdenum four kinds of materials,the use of percussion drilling and spiral scanning drilling two processing methods,in a vacuum,Drilling in air and water environment.The effects of laser space shaping,pulse energy,pulse number and repetition frequency on the size and taper of the borehole were studied,and the processing parameters were optimized.