| Tm3+-doped fiber lasers in industrial, medical, scientific and military fields has an important application prospect. Fiber Bragg Grating (FBG) is an important component of fiber lasers. FBG-based fiber laser has some excellent characteristic with narrow linewidth output, simple structure, stable performance, easy maintenance and so on. However, Tm3+-doped silica fiber is not photosensitive.It is difficult to inscribe FBG into its core with UV-pulsed laser. The refractive index change of FBG obtained is too small to meet the application requirements, even if its photosensitivity is improved by the sensitization technology. It hinders the all-fiber-based development of Tm3+-doped fiber laser. In recent years, a new technique attracted wide attention from academics and engineering, which inscribed FBG in the non-photosensitive fiber using near-infrared ultrashort pulse laser. With the traditional techniques inscribing FBG using UV-pulsed laser in photosensitive fiber compared to, this method has a greater value. In this paper, the technology inscribing FBG with femtosecond pulsed laser and related theories are systematically studied.Based on coupled-mode theory that is the basic equation of fiber Bragg grating, the spectral characteristics of sinusoidal and rectangle refractive index modulation single-mode uniform FBG is analyzed, and the impact of structural parameters of FBG on its performance is obtained. Second-order FBG reflection spectrums with these two forms of index modulation are simulated, and high-order response of rectangular index modulation FBG is found, it could provide theoretical foundation for the fabrication of high-order FBG. Probable resonant wavelengths of multi-mode FBG are calculated from the Phase-match standpoint, and are confirmed by solving coupled-mode equations with two models. Simultaneously, the effects of excitation conditions on the multi-mode FBG spectral are analyzed. Two kinds of numerical method are introduced to remedy defects of coupled-mode theory, which can be used to analyze the characteristics of non-uniform FBG. The reflectance spectra of Gaussian apodizing index modulation FBG is obtained by Rouard's method.The interactions between 800nm femtosecond laser pulses and silicon-based fiber cladding, Yb3+, Tm3+-doped fibe core are analyzed theoretically and researched experimentally by using Z-scan technology. The important conclusions is found by fitting the experimental data with normalized transmittance formula, which the interaction between 800nm femtosecond laser and these media is a five-photon nonlinear absorption proceeding. And the corresponding non-linear absorption coefficient is obtained, is respectively 10-47cm7/W4, 10-47cm7/W4 and 10-50cm7/W4. Type I-type damage threshold value of silicon-based fiber cladding and Yb3+-doped fiber core is investigated with non-linear transmission experiments, is respectively 14.5TW/cm2 and 13TW/cm2. However, the corresponding threshold of Tm3+-doped fiber core can not accurately obtain due to resonance absorption of Tm3+ on 800nm laser.The effects of phase-mask parameters on interference fringes are analyzed mainly based on grating equation and wide-width characteristics of femtosecond laser. The rational principle for design of the phase mask is get, and the optimal distance between the fiber and phase mask is calculated. The impact of cylindrical fiber inner cladding on focus is studied by Gaussian beam optics and paraxial approximation, and the focal length of focusing lens using for phase mask method is calculated.Two key technical problems about inscribing system of point-by-point method are solved. Firstly, the experiment about the fiber imaging under the microscope is carried out, the imaging system based on CCD cameras is built in order to solving alignment problem of point-by-point method inscription. Secondly, the methods to eliminate cylindrical lens effect are analyzed, a solving method that is suitable for fibers used in this experiment is proposed. The feasibility of these two methods is verified through experiments.The method tuning the period of phase mask using lens imaging technology is theoretically discussed, which can improve the limitation of phase mask method, the changing trends of FBG wavelength with tuning parameters is proposed. The analysis results show FBG wavelength can be continuously tunable within a certain range by using this method. In the experiment, four FBGs with different wavelengths are achieved using the same phase mask by adjusting the distance between phase mask and fiber, as well as the distance between phase mask and tuning lens. The inscribed FBG wavelengths range is between 1882.5nm and 1970.8nm, and to achieve the laser output operation in corresponding wavelenth.The relationship between output power and cavity mirror reflectivity of fiber laser is obtained through the analysis of output characteristic of linear cavity Tm3+-doped double-clad fiber laser. Reflection wavelength and reflectivity of the experiment obtained FBG can be quantitated taking advantage of this relationship and output laser wavelength and power: reflectivity of FBG static inscribing into Tm3+-doped single-mode and multi-mode fiber is greater than 93.7% and about 5.3%, respectively. A 12mm-long FBG is wrriten into an octagonal Tm3+-doped double-clad fiber using phase mask scanning technology, its peak reflection was about 89% at 1960nm. solve the problem that reflectivity of multi-mode FBG is low is slove by phase mask scanning technology. Finally, the reasons of inscription failure for point-by-point method are analyzed, and solutions are proposed.
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