Fig. 1. Characterization of the GNSs and GNS film. (a) TEM image of GNSs at scale of 100 nm; inset: photographs of GNS aqueous solution and the TEM image of GNSs at a scale of 20 nm. (b) SEM image of GNS film at scale of 500 nm; inset: the photograph of GNS film.

Fig. 2. Absorption spectra of GNS solution (red line) and GNS film (black line).

Fig. 3. Setup of measurement of saturable absorption by balanced twin detector measurement technology.

Fig. 4. Dependence of the transmittance of the GNS film on the incident pump peak power density.

Fig. 5. Schematic of the experimental setup for the GNS based passively Q-switched EDFL. Laser diode (LD), wavelength division multiplexer (WDM), Er3+ doped fiber (EDF), isolator (ISO), output coupler (OC), optical spectrum analyser (OSA). Inset: TEM image of GNS.

Fig. 6. Q-switched pulse output characterization in the EDF laser cavity with a GNS SA. (a) Optical spectra of CW laser and Q-switched pulsed laser. (b) Pulse train and (c) single pulse characteristics of Q-switched pulsed laser for a pump power of 120 mW. (d) Pulse repetition rate and pulse width versus pump power.

Fig. 7. Measured emission spectra of the Q-switched laser based on the GNS SA.

Fig. 8. Relationship between the average output powers and pump powers.