Effect of TEOS addition on formation of Au metal nano-particles in the Au-doped optical fiber and its optical nonlinearity

Optical fiber incorporated with Au metal nano-particles (MNPs) in the fiber core was manufactured by using tetraethyl-orthosilicate (TEOS) as a reduction agent in doping solution containing Au ions during the modified chemical vapor deposition (MCVD) process concurrently adopting solution doping process. The TEOS in the doping solution played an important role to provide reduction atmosphere during the fiber fabrication at high temperature (above 2100 °C) due to the formation of silica glass networks by sol–gel process. The formation of Au MNPs with the average diameter of 8 nm in the preform core was confirmed by transmission electron microscopy (TEM) analysis. The absorption peak appeared at 490 nm was attributed to the surface plasmon resonance (SPR) of the incorporated Au MNPs in the fiber core, and the nonlinear refractive index, n2, of the fiber was found to be 2.96–1.27 × 10−16 m2/W at the pump power from 12 to 100 mW.