Wavelength-Tunable Er $^{3+}$ -Doped fs Mode-Locked Fiber Laser Using Short-Pass Edge Filters

We demonstrate a wavelength-tunable Er³⁺-doped femtosecond mode-locked soliton fiber laser by incorporating a short-pass edge filter into a ring cavity. When the filter is thermo-optically tuned toward shorter wavelengths to strongly attenuate the wavelengths longer than the cutoff, the constituting wavelengths of the mode-locked fiber laser move to shorter wavelengths and the laser center wavelength can be tuned over 1539.7 ~ 1560 nm. The cavity dispersion is preset in the deep soliton region to keep small fluctuations of laser pulsewidth when the laser wavelength is tuned.