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

Fiber-grating-based self-matched additive-pulse mode-locked (APM) fiber las ers were investigated both theoretically and experimentally. With three fib er gratings to form the linearly coupled cavities, such a fiber laser syste m could generate stable mode-locked output without critical cavity length c ontrol. It was shown that the wavelength dependence of the effective penetr ation length of a fiber grating led to the self-matching of the cavity leng ths of the coupled cavities, A millimeter-order cavity-length mismatch coul d be tolerated. In a similar laser structure using chirped fiber gratings w ith a designated arrangement of the grating polarities, the APM fiber laser could have the advantages of higher tolerance of cavity-length mismatch an d stretched-pulse amplification. After pulse compression with a piece of si ngle-mode fiber, output pulses with full-width at half-maximum pulsewidths of 930 fs were obtained.