NCF–GIMF device as SA and filter utilized in tunable single- and dual-wavelength Yb-doped mode-locked fiber laser

Abstract

In this letter, by incorporating hybrid structure of no-core fiber (NCF)-graded index multimode fiber (GIMF) as the saturable absorber (SA) and spectral filter simultaneously, not only the switchable noise-like pulses (NLPs) but also the tunable single- and dual-wavelength dissipative solitons (DSs) are obtained from a net normal dispersion Yb-doped mode-locked fiber laser. The NCF–GIMF​ device plays a crucial role in the pulse generation and the wavelength tuning. By means of being stretched, the transmission peak of the NCF–GIMF device can be tuned over 60 nm which is responsible for the wavelength tuning of the oscillator. As the SA, the NCF–GIMF device affords variable saturable absorption properties during the stretching process which are suitable for the ultrafast soliton generation. Based on this device, the center wavelengths of the NLPs are demonstrated to be switchable from 1034.6 nm to 1072.2 nm. The single wavelength DSs with the pulse width at the level of tens of picoseconds can be tuned from 1026.3 nm to 1080 nm. Additionally, the dual-wavelength asynchronized DSs with a spectral interval of 21 nm have a wavelength-tunable range of 13 nm. This all-fiber ultrafast Yb-doped laser with tunable and flexible outputs can satisfy diverse application needs.