Ultrashort stretched-pulse L-band laser using carbon-nanotube saturable absorber

In the paper, a passively mode-locked erbium-doped fiber ring laser in the long-wavelength band (L-band) is presented by using a single-wall nanotube saturable absorber (SWNT-SA). The optical properties of the SWNT-SA are compared with those in the C-band in view of the absorbance spectrum and the power-dependent transmittance of the SWNT-SA film. The effects of the net cavity dispersion and the length of the erbium-doped fiber (EDF) on L-band stretched pulse generation are discussed. The designed stretched-pulse L-band laser has a net dispersion of 0.017-ps² and generates ultrashort (110 fs), broad-spectrum (41 nm) pulses with a signal-to-noise ratio over 70 dB.