Femtosecond laser nanofabrication of metal structures through multiphoton photoreduction

We present an ultrafast laser technique for direct-writing gold and silver structures of tunable dimensions. By utilizing nonlinear optical interactions between chemical precursors and femtosecond pulses, we limit metal-ion photoreduction processes to focused spots smaller than that of the diffraction-limit. This creates metal nanostructures in a focal volume that can be rapidly scanned in 3D. By varying the solution chemistry and laser pulse parameters, we demonstrate morphological control of the resulting structures. We fabricate grid and woodpile patterns over hundreds of micrometers in dimensions. We show the process is scalable and possesses optical characteristics suitable for SERS or metamaterial applications.