Enhanced optical gain assisted by the plasmonic effects of Au nanoparticles in Nd³⁺ doped TeO₂-ZnO waveguides produced with the pedestal architecture

Investigation of the signal enhancement of Nd³⁺ codoped TeO₂-ZnO pedestal waveguides, at 1064 nm, due to Au nanoparticles deposited over the core is presented for the first time. Nd³⁺ doped TeO₂-ZnO thin film was obtained by RF Magnetron Sputtering deposition. The resulting core with 500 nm height and widths in the 4–40 μm range, exhibited low roughness average in all area measured (0.48 ± 0.04) nm. Minimum propagation losses of 2.2 dB/cm were observed for waveguide width of 40 μm whereas an increase took place for smaller ones. Scanning electron microscopy (SEM) allowed the waveguide structure inspection and transmission electronic microscopy (TEM) the Au nanoparticles evaluation. The results showed that the Au nanoparticles contributed up to 75 % of relative gain enhancement, under 808 nm excitation. This increase was due to the local field growth in the proximity of the nanoparticles that enhances the density of excited Nd³⁺. The internal gain that considers the propagation losses reached positive values for larger core widths (above 8 μm).

The present study opens possibilities for optical amplifiers with low propagation losses based on different metal-dielectric composites, as well as other waveguide-based devices.