An Easily Switchable Dual-Wavelength Passively Mode-Locked Erbium Fiber Laser

A simple scheme of switchable dual-wavelength passively mode-locked fiber laser is demonstrated. The laser can be flexibly switched among different mode-locked states simply by tuning the cavity loss while keeping all the other cavity parameters fixed. As the cavity loss increases, the mode-locked fiber laser operates at the long-wavelength, dual-wavelength, and short-wavelength states, successively. In addition, these states can be conveniently switched without losing the mode-locked operation and the switching process is reversible as the cavity loss decreases. The mechanism is qualitatively explained by the balance between the fiber gain and the cavity loss.