We show that the spectral response of a Fabry–Perot semiconductor saturable absorber depends on laser beam focusing. We used this effect to achieve stable passive mode-locked operation in a simple and environmentally stable fiber laser by introducing spectral filtering and forcing near-resonant operation. By reducing the free spectral range and increasing the nonlinear response of the Fabry–Perot saturable absorber, we obtained dual-wavelength mode-locked operation.
© 2000 Optical Society of America
(060.2380) Fiber optics and optical communications : Fiber optics sources and detectors
(060.2410) Fiber optics and optical communications : Fibers, erbium
(320.7090) Ultrafast optics : Ultrafast lasers
(320.7130) Ultrafast optics : Ultrafast processes in condensed matter, including semiconductors
O. G. Okhotnikov and M. Guina, "Stable single- and dual-wavelength fiber laser mode locked and spectrum shaped by a Fabry—Perot saturable absorber," Opt. Lett. 25, 1624-1626 (2000)