Mode-locked All Polarization-maintaining Fiber Laser Based On A Nonlinear Amplifying Loop Mirror

The performance of ultrafast pulsed lasers is stable and easy to operate.Therefore, there is a great promise by applying ultrafast pulsed fiber laser in the fields of micro-machining, terahertz, medical diagnosis and spectroscopy.In recent years, the performance and stability of femtosecond fiber lasers have been significantly improved, but to further increasing the energy of the pulses and reducing the duration of the pulses, it is necessary to further study the fiber lasers.In this paper, we intensively study the 1550nm opticle fiber laser based on the nonlinear optical loop mirror and dispersion management cavity. The laser is all polarization maintaining. Research works are as follows:(1) Summarizes the research background and significance of the research subject, and summarizes the present research situation and the application of the laser.(2) Based on fiber nonlinearity theory and dispersion theory, the pulse transmission theory is introduced and the principle of non-linear optical loop mirror is analyzed in detail. After analyzing the advantages and disadvantages of various mode locking techniches, we choose the nonlinear optical loop mirror as the mode locking device of the laser in this paper, through which we can realize all-fiber structure laser with good environmental stability.(3) The theory of dispersion management lasers is studied, and the commonly used dispersion management technology is introduced. By designing the dispersion-managed fiber laser based on NALM, we effectively avoid the wave splitting phenomenon and finally obtain the laser with pulse energy of 0.8nJ and the pulse duration is 1.6ps.(4) In order to further reduce the pulse duration and increase the pulse energy, we introduce many commonly used pulse compression technology,and pulse compression technologies. And we designed an amplification system based on erbium-doped fiber amplifier, after which the pulse duration is successfully compressed to 100fs with single pulse energy increased to 10nJ.(5) The generated femtosecond laser pulse is incident on DAST crystal,and 100nW terahertz is successfully obtained by optical rectification, which proved that the femtosecond fiber laser in this paper has very good practical value.