In this paper, we present a theoretical model to describe the passively-Q output characteristics of quasi-three level Ho3+-doped Fluorotellurite fiber lasers. According to the model, we have studied the factors impacting on the output characteristics of the laser through numerical simulation method. The calculating program of the theoretical model is written using the Matlab language. We obtain the passively-Q output laser with the pulse repetition rate of 13.1 kHz, pulse width of 28.63ns, peak power of 25W, and pulse energy of 0.34 μJ at the pump power of 0.1W. When the pump power increases, the pulse width of the laser decreases, the pulse repetition rate linearly increases, both the pulse energy and the peak power also increases. The pulse width of the laser linearly increases and the pulse energy increases when the length L does. When the output coupler transmission T increases, both the pulse width and the peak power of the laser decrease. The pulse energy of the laser firstly increases and then decreases when the output coupler transmission T does. We qualitatively analyze what causes the change laws of the outputlaser characteristics, such as the pulse width and the pulse energy.
16-core photonic crystal fiber (PCF) was designed. In order to obtain spatially flat in-phase modes, the super-mode near- field properties were studied through method of numerical simulation calculation and according to coupled mode theory. On the based of the scalar Fraunhofer Diffraction, a far- field in-phase super-mode theoretical modeling was presented. According to the modeling, one discussed the influence of the random phase perturbation, the random amplitude perturbation and the polarization direction perturbation on the far-filed intensity distribution, in detail. The results show that both phase perturbation and amplitude perturbation sharply impact the far-filed distribution of interference intensity and contrast. However, the influence of the polarization direction perturbation is not obvious. When the parameterδ, μ and ▵ increases, the field center intensity decreases and the power of the central spot also does, which means the profile of the spot will blur and the beam quality drop.