Fig. 1. (a) Prepared SWCNT-SAM. Inset: dispersion of SWCNT. (b) TEM image of SWCNT in coarse resolution. (c) TEM images of SWCNT in fine resolution. (d) Raman spectrum of SWCNT-SAM.

Fig. 2. (a) Linear and (b) nonlinear reflection characteristics of SWCNT-SAM. (c) Schematic of the setup for characterizing saturable absorption.

Fig. 3. Experimental setup of the 3.5 µm mode-locked fiber laser and the diagram showing the transition processes involved in the generation of the 3.5 µm radiation.

Fig. 4. Characteristics of the 3.5 µm mode-locked pulses: (a) optical spectrum, inset: optical spectrum in linear format; (b) pulse train; (c) RF spectrum around the fundamental frequency, inset: RF spectrum in a 500 MHz span. (d) Damaged surface of SWCNT-SAM, inset: pulse train of the Q-switched pulses.