Plasmonic hotspots on laser-treated AgO^x thin film: A novel nanofabrication technique for plasmonic substrate

Using a femtosecond laser, the laser-direct-writing technique has been transformed into a highly efficient method that can rapidly process glass substrate into structures of Ag nanoparticles that provide plasmonic enhancement. The processed AgOx thin films showed enhanced optical absorption over a broad spectral range. The plasmonic hotspots on the treated area are also probed with dyed polymer beads drifting in the water solution. Multilevel Raman enhancements can also be achieved by varying the incident femtosecond laser power. Moreover, the processing rate is much faster than other reported laser-direct-writing techniques with either continuous or nano-second lasers. This proposed technique has great potential for the fabrication of plasmon-active substrate with high throughput and efficiency.