Fiber-grating-based self-matched additive-pulse mode-locked fiber lasers

Fiber-grating-based self-matched additive-pulse mode-locked (APM) fiber lasers were investigated both theoretically and experimentally. With three fiber gratings to form the linearly coupled cavities, such a fiber laser system could generate stable mode-locked output without critical cavity length control. It was shown that the wavelength dependence of the effective penetration length of a fiber grating led to the self-matching of the cavity lengths of the coupled cavities. A millimeter-order cavity-length mismatch could be tolerated. In a similar laser structure using chirped fiber gratings with a designated arrangement of the grating polarities, the APM fiber laser could have the advantages of higher tolerance of cavity-length mismatch and stretched-pulse amplification. After pulse compression with a piece of single-mode fiber, output pulses with full-width at half-maximum pulsewidths of 930 fs were obtained.