| Double-cladding photonic crystal fiber (DC-PCF) has a lot of excellent traits, such as the endlessly single mode and large effective mode area, thus it has considerably important potential application and research significance in the area of high power fiber lasers. In this paper, theoretical analysis and experimental research on Yb3+-doped DC-PCF (YD-DC-PCF) lasers were investigated respectively.We introduced the basic structure, light guiding theory and special properties of PCF, analyzed the mode area distribution of the domestic YD-DC-PCF in experiment based on the finite element method, and computed theoretically the effective mode area, numerical aperture, nonlinear coefficient, normalized frequency and dispersion characteristics of this PCF.And then, we had a brief introduction to the basic theory and main pump methods of YD-DC-PCF lasers, further researched the power transmission characteristics of YD-DC-PCF lasers based on the continuous-wave DC-PCF laser’s steady rate equations and analyzed theoretically effects on the laser’s output characteristics from different pump methods, which provided the theoretical guidance for optimization and designing of YD-DC-PCF lasers.Lastly, we studied experimentally the YD-DC-PCF lasers. Firstly, using the YD-DC-PCF from NKT as the gain medium, we investigated how pump methods produced effects on the laser’s output characteristics:the slope efficiency of the forward-pumped laser was10%, but the backward-pumped one had the slope efficiency at13%. Secondly, we used a laser diode to pump backward the domestic YD-DC-PCF and examined its output characteristics with different cavity structure:we used a dichroic flat mirror and a dichroic flat-concave mirror as the back cavity-mirror respectively. There existed the model competition phenomenon in the first laser, and its line width of output laser was about5nm. While another one was above lOnm. Besides, the slope efficiency of the former was11%, and the latter’s was just9%. |
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