Systematic exploration and characterization on the influence of dispersion to pulse characteristics in Tm-doped NPE mode-locked fiber oscillator

We present a systematic and experimental exploration on the influence of the second-order and third-order dispersion on pulse characteristics in an ultra-high numerical aperture (UHNA) fiber dispersion-managed, Tmdoped and nonlinear polarization evolution (NPE) mode-locked fiber laser cavity; and obtained the detailed regularity of the variation of the key parameters for mode-locked pulse, including pulse duration, pulse spectral profile, and pulse signal-to-noise ratio (SNR) with dispersion. In this process, we find that there are two interesting second-order dispersion points of -0.207 ps2 and 0.09 ps2, in which the pulse SNRs can be optimized to as high as 79 dB and 78 dB, respectively, considerably higher than that in other positions. Besides, the experimental results show that the value of third-order dispersion can not only impact the pulse spectrum but also monotonously affect the quality of pulse SNR. To the best of our knowledge, this is the first report on the detailed analysis of the effects of both the second and the third-order dispersion values on the pulse characteristics in 2 mu m mode-locked fiber laser cavity and it will be an important reference to the realization of a Tm-doped modelocked laser with high pulse contrast.