| Rare-earth-doped fiber lasers have been concerned because of many merits such as high conversion efficiency, excellent output beam quality, and eminent compact ability. Relative to traditional solid lasers or gas lasers, fiber lasers have great advantage on account of small size and light weight in the field of space detection. This article mainly studies the tunable output characteristics of Q-switched double-clad fiber lasers, analyses the feasibility of tuning pulse width and repetition frequency, and shows some basic experiment results.The basic principles of the Q-switched rare-earth-doped fiber lasers are been introduced and some major key technologies are been analyzed. Base on the principles, the influence of different conditions of the double cladding Yb3+ -doped continuous-output fiber laser on the output power has been analyzed. After that, point model and traveling wave method model are been applied to discusses different parameters'impact on the characteristics of pulse derived from Q-switch fiber laser. According to the analysis, we explain multi-peak of the output pulse, and also we find out that the pulse width of Q-switched fiber laser can vary continuously within dozens of nanoseconds in a certain pump modulation range. Besides, pulse repetition frequency can be controlled by adjusting the frequency of the switch. So a proposal is advanced which control the pulse repetition rate by adjusting the frequency of switch and tune the pulse duration from 121ns to 195ns through adjusting pump power and reflection rate of a FBG.Finally, utilizing the Er3+-Yb3+ doped fiber as gain media, fusing optic couples, optic isolator and some other devices, an Q-switched fiber ring laser which emit stable pulse sequence with 45Hz repetition rate is experimentally demonstrated. In addition, we conclude that jitter and rise time of the Q-switch about milliseconds scale will affect the output pulse characteristics, to bring about multi-pulse. |
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