Fiber Surface Waveguide Devices Fabrication By Femtosecond Laser And Its Sensing Performance Research

The rapid development of communication networks has accelerated the application process of Internet of Things technology.Nowadays,smart homes,unmanned driving,smart cities,etc.are gradually being integrated into people's daily lives,bringing more convenience to people.As an emerging product,the Internet of Things has a more complex architecture and no unified standards,and security issues in all aspects are more prominent.The key implementation technology is the sensor network.In the natural environment exposed by sensors,how to maintain the integrity of the network for a long time has become a new direction for the development of sensing technology.Optical fiber sensors are highly favored for their excellent performances such as anti-electromagnetic interference,insulation resistance,corrosion resistance,small size,light weight,and access to the network for remote monitoring.The evanescent field optical fiber sensor studied in this subject is a very important one.The evanescent field optical fiber sensor was originally used solely to measure the change in the refractive index of the solution in the external environment.With the rapid development of biological detection,nanomaterials and semiconductor materials research,the size of the substrate device has become higher and higher,so the evanescent field fiber sensor with its small size can generate evanescent waves on the surface of the fiber(That is,light energy)and other characteristics are understood and used by many scholars.However,the traditional evanescent field fiber sensor still has some problems that are not conducive to its use in actual environments,such as the inability to balance the relationship between evanescent field strength and mechanical strength.This thesis combines fiber optic sensing technology with femtosecond laser direct write optical waveguide technology to create a new type of evanescent field fiber optic sensor,which solves this problem well and conducts in-depth research on it.The specific contents are as follows :Chapter 1: Introduction.This paper briefly introduces the research significance of this topic on the development of Internet of Things technology,summarizes the advantages and problems of the three types of evanescent field fiber optic sensor structures,and lists the application directions of evanescent field fiber optic sensors;The research progress of the second laser writing optical waveguides inside the bulk glass,on the surface of the bulk glass and inside the optical fiber leads to the research content of this topic.Chapter 2: Femtosecond laser preparation of optical waveguide technology.Before making a new type of evanescent field optical fiber sensor,the principle of femtosecond laser and transparent material interaction to prepare an optical waveguide and the femtosecond micromachining system were first introduced;then by changing the pulse energy and platform displacement speed of the femtosecond laser The transmission loss of the optical waveguide is optimized,and the low-loss transmission of 0.1 dB / mm of light in the laser waveguide is realized.Finally,the two parameters of the refractive index modulation and the mode field profile,which measure the quality of the optical waveguide,are measured.Chapter 3: Mach-Zehnder Interferometric Refractive Index Sensor for Optical Fiber Surface Waveguide.Optical fiber Mach-Zehnder interferometer is a kind of structure that is widely studied in optical fiber sensors.Its sensing principle is simple and it is easy to manufacture.In order to explore the feasibility of this subject,this paper uses this structure to make a Mach-Zehnder interferometric sensor based on fiber surface waveguide.This article describes the sensor's sensing principle,refractive index response and temperature response test method in detail.The experimental results show that the sensor is sensitive to changes in the refractive index of the external environment,and the sensitivity at the refractive index of 1.432 is as high as 3000 nm / RIU.Due to the advantages of the structure,the sensor is not only insensitive to temperature,but also has high mechanical strength.Chapter 4: Coated Fiber Surface Waveguide SPR Index Sensor.In order to verify that the evanescent field strength of the fiber surface waveguide can interact with a certain thickness of nano-materials,this topic uses the method of gold plating on the fiber surface to fabricate the fiber SPR sensor.In this paper,the working principle of the optical fiber SPR sensor and the preparation process of the optical fiber surface waveguide SPR sensor are introduced in detail,and the refractive index response is tested.The experimental results show that the sensor is very sensitive to the refractive index of the external environment like the traditional optical fiber SPR sensor,and the sensitivity measured at the refractive index of 1.395 is 3352 nm / RIU.Finally,the SPR model of the fiber surface waveguide is numerically simulated,and the simulation data is compared with the experimental data.The results show that the experiment and simulation have a high degree of agreement.