Fig. 1. Cavity setup of tunable mode-locked PDFFL.

Fig. 2. Nonlinear absorption curve of the SWCNT SA. The inset shows the Raman spectrum. Reprinted with permission from Ref. [44], Science Press.

Fig. 3. Average output power against pump power. Different marker color represents different laser operation. The inset shows the oscilloscope trace of QML and CWML operations.

Fig. 4. Characteristics of mode-locked PDFFL at pump power of 556 mW. (a) Optical spectrum [inset (I), pulse train and (II), autocorrelation trace (dotted line) with Gaussian fit (solid line)] and (b) RF spectrum. Inset (I) shows the RF spectrum with a 500 MHz span and (II) gives the optical spectrum stability of the mode-locking operation over a period of 1 h.

Fig. 5. Mode-locked output spectra at different central wavelengths with the incorporation of a tunable Mach–Zehnder filter, covering a tuning range of 11 nm.

Fig. 6. Overview of mode-locked fiber lasers using different low-dimensional material SAs, which are classified in terms of operating wavelength and pulse width.