Study On Narrow Linewidth Fiber Laser

The narrow linewidth fiber laser with a very narrow spectral linewidth and a very long coherence length is a core device in applications such as coherent optical communication,fiber sensing,and laser radar,widely used in many fields.Nowdays,two main ways to achieve narrow linewidth fiber lasers are through saturable absorbers and ultrashort cavities.However,the saturable absorber for narrow linewidth fiber lasers mainly uses gain fibers,which have less selectivity,and the new two-dimensional material saturable absorbers with excellent performance are less studied for implementing narrow linewidth fiber lasers.More types of saturable absorbers still need to be explored.The ultra-short cavity,although simple in structure,is also limited by factors such as the bandwidth of the filter,the length of the laser cavity,and narrow linewidth fiber lasers based on ultrashort cavities mainly use specially made highly doped fibers.Therefore,the development of narrow linewidth fiber laser technology and key components is of great significance.This thesis focuses on the realization of key devices and laser technologies for narrow-linewidth fiber lasers.The main research contents include the following three aspects:1.The nonlinear optical properties of Ni-MOF(Metal-Organic Frameworks)materials are studied.The narrow-linewidth fiber lasers based on MOFs are studied.The linewidth of the laser is 3.2 kHz,the output power is 1.07 mW,and the output power fluctuation is less than 1.3%.The signal to noise ratio is greater than 52 dB.2.A method and theoretical model for implementing ultra-narrowband filters using filter series and multiple reflections are studied,and a narrow linewidth fiber laser is realized by this method.The results show that the filter method can reduce the bandwidth of the filter from 0.07 nm to below 0.0025 nm,and the narrow linewidth fiber laser’s output has a 3 dB linewidth of 941 Hz,power fluctuation less than 2.5%,and signal-to-noise ratio greater than 66.dB.3.A kind of ultra-short cavity single-frequency fiber laser is obtained by engraving the grating on the gain fiber to realize the integration of the filter grating and the gain fiber.The laser has a cavity length of 2.5 cm,an output 3 dB linewidth of 12.892 kHz,an output power instability of less than 1.7%,and a signal power to noise power ratio greater than 60 dB.