Research on the Passively Mode-locked Er~(3+)-doped Fiber Laser

摘要

This work is motivated by the need to ultra-short optical pulses for realizing OTDM/WDM. As an attractive ultra-short pulse source, the mode-locked fiber laser attracts more and more attentions. In this paper, we proposed a novel method to design passively mode-locked fiber laser by combining lumped-gain amplification and high output couple ratio. On the one hand, through using lumped-gain amplifier as the amplifying units in the cavity, the mode-locked fiber laser can effectively reduce the periodic energy fluctuation of intra-cavity and offer a very good suppression to the spectral sidebands. On the other hand, a coupler with high output couple ratio is used in the cavity to enhance the output single-pulse energy. The characteristics of the presented laser have been investigated theoretically and experimentally in detail. With this method, a passively mode-locked Er~(3+)-doped fiber laser with high spectrum quality and high single pulse energy is obtained. The experimental results show that its spectral sidebands suppression ratio is more than 20dB, the maximum average output power is about 18mW and the single pulse energy is about 1.2nJ with pulse-width 200fs at a repetition of 14.2MHz.