A novel method for passively mode-locked fiber laser to enhance sidebands suppression ratio by using lumped-gain amplification

A novel method to design a passively mode-locked fiber laser with high sidebands suppression ratio by using lumped-gain amplifier as the intra-cavity amplifying units is first proposed and experimentally demonstrated in this paper. The theoretical and experimental results show that the proposed fiber laser can effectively reduce the periodic energy fluctuation of intra-cavity and offer a very good suppression to the spectral sidebands. With this method, a passively mode-locked Er
³⁺
-doped fiber laser with spectral sidebands suppression ratio of more than 20dB is obtained.