$Q$ -Switched Erbium-Doped Fiber Laser Based on Silver Nanoparticles as a Saturable Absorber

We demonstrated saturable absorbers (SAs) based on silver nanoparticles (SNPs) by depositing them on the end facet of the fiber. The SNPs-based SAs showed large modulation depths and high maximum transmittances. With one of the SNPs-based SA, we built a passively
$Q$
-switched erbium-doped fiber laser (EDFL). Self-started
$Q$
-switching at 1564.5 nm in the EDFL was achieved for a threshold pump power of 19.9 mW; 2.4-
$\mu \text{s}$
pulses with a repetition rate of 58.5 kHz and maximum single pulse energy of 132 nJ were achieved at a pump power of 139 mW. The obtained results showed the possibility of SNPs serving as a high performance SA for a
$Q$
-switched fiber laser.