Fig. 1. Experimental setup for fabrication and parameter measurement of saturable absorber (inset is nonlinear transmittance curve of CNT-SA)

Fig. 2. Structural diagram of multi-wavelength mode-locked Er-doped fiber laser

Fig. 3. Pulse output characteristics under wavelength-tunable mode locking. (a) Spectral variation map (inset is mode-locking spectrum at 1551.18 nm); (b) oscilloscope curve at 1551.18 nm mode-locking; (c) autocorrelation curve at 1551.18 nm mode-locking; (d) radio frequency spectrum at 1551.18 nm mode-locking

Fig. 4. Pulse output characteristics of asynchronous dual-wavelength mode locking. (a)(d) Spectra; (b)(e) are the oscilloscope traces; (c)(f) radio frequency traces