A femtosecond hybrid mode-locking fiber ring laser at 409 MHz

We report on a 312 fs all-fiber ring laser with a fundamental repetition rate of 409 MHz based on an Er3+/Yb3+ codoped phosphate glass fiber, which is only 5.0 cm in length. Such a high repetition rate femtosecond fiber laser is realized by combining an optical integrated module and a hybrid mode-locking method, where a semiconductor saturable absorber mirror ensures the self-starting mode-locking and a nonlinear polarization evolution technique provides a pulse shortening mechanism. With a transmission-type saturable absorber, the fundamental repetition rate of a hybrid mode-locking all-fiber ring laser is expected to be further scaled up with a much more compact cavity structure. (letter)