Fig. 1. Experimental setup of the QML MMF laser with a GMM.

Fig. 2. (a) Microscope image of the fabricated GMM; (b) nonlinear saturable absorption curve and the corresponding fitting curve of the fabricated GMM; (c) spectral filtering characteristic of the fabricated GMM.

Fig. 3. QML operation at the pump power of 1.40 W. (a)–(c) QML pulse-train in the time range of 200 µs (20 µs/div), 20 µs (2 µs/div), and 200 ns (20 ns/div), respectively; (d) the corresponding optical spectrum; (e) the RF spectrum; (f) the beam profile.

Fig. 4. Wavelength-tunable QML operation at the pump power of 1.40 W.

Fig. 5. Pump-dependent characteristics of the single-wavelength QML operation. (a) QML pulse-train under different pump power; (b) the pulse envelope width and repetition rate versus the pump power; (c) the average output power and pulse energy versus the pump power.

Fig. 6. Single-wavelength fifth harmonic QML operation at the pump power of 1.40 W. (a) The Q-switched envelope in the time range of 20 µs (2 µs/div), while the inset is the pulse-train in the time range of 200 µs (20 µs/div); (b) the mode-locked pulse-train underneath the Q-switched envelope in the time range of 200 ns (20 ns/div); (c) the RF spectrum; (d) the beam profile.

Fig. 7. Characteristics of the dual-wavelength QML operation. (a) The dual-wavelength spectra with different wavelength spacings at the pump power of 1.40 W; (b) the QML pulse-trains under different pump powers at the central wavelengths of 1030.48 nm and 1033.78 nm.