Research On Narrow Linewidth Erbium-doped Photonic Crystal Fiber Laser

Narrow linewidth fiber lasers have wide applications in lidar,optical fiber remote sensing,laser ranging and coherent optical communication as a light source because of its narrow linewidth and high laser coherence.The main purpose of this paper is to design a narrow linewidth fiber laser which satisfies the application of resonator fiber optic gyroscope.At the same time,we add a certain nonlinear and slightly anti radiation photonic crystal fiber to further study and analyze its linewidth characteristics.The main work is as follows:(1)Through analysis of the factors affecting the linewidth,we can obtain the important relationship between random phase fluctuation and the life of intracavity photon.By using Anti-seismic and constant-temperature externally,designing the resonator intrernally or the spontaneous emission of the gain medium are all closely related to the linewidth.Therefore,we analyzed and discussed the cavity shape and the key technologies of the narrow linewidth in detail.Also,the optical path structure is selected and the delayed self heterodyne linewidth measurement system is set up.(2)Baesd on the optical path,we set up the active ring resonator model with a saturable absorber.Then,we simulated the porcess of the laser startup and formation of the reflection spectrum numerically.First,the active ring resonator model of the optical power transmission of the longitudinal modes in the active cavity is analyzed,and the boundary conditions of the traveling wave cavity are formed.After understanding the importance of the reflection spectrum to the active traveling wave cavity,we aim at the model of to analyze the linewidth compression from saturated absorber.Through the series of changes in the length of the un-pumped erbium fiber,the doping concentration and the optical power injected into the structure of mode selected package,the variation rule of the reflection spectrum range and depth is displayed.Based on the above models,three output cavity structures are enumerated,and the porcess of the laser startup and formation of the reflection spectrum is simulated and optimized.(3)Conducted the research of the narrow linewidth erbium-doped photonic crystal fiber laser.Three kinds of cavity structures are built respectively,and their spectral output characteristics and line width characteristics of self heterodyne measurement are analyzed.To adjuest the parameters of saturable absorber,we verify that the experimental results are consistent with the simulation of reflection spectrum.Experimental research found that photonic crystal fiber showed the characteristics of inhibition of linewidth broadening as the gain fiber and satisfy the interference conditions to complete the saturable absorber effect in the absence of a polarization controller as the saturable absorbe which show the potential of saturable absorption.The three structures realized the use of photonic crystal fiber as gain fiber to get narrow linewidth output below 2.2KHz,and the output of optical power is milliwatts.Though not high,it can satisfy the use of resonator fiber optic gyroscope.(4)The optical path of tunable erbium-doped photonic crystal fiber laser is built by using the electronic controlled narrow linewidth filter.After comparing three cavity structures,the best output postposition structure of wavelength stability is selected as the construction of tunable optical path.The narrow linewidth tunable laser in 61.02 nm wavelength range is achieved,and the output linewidth is 2.2KHz.At any temperature of 5-55 degrees,it can maintain wavelength stability within one hour 0.03 nm.