Femtosecond laser micromachining of TiO2 crystal surface for robust optical catalyst

The two-photon laser ablation of TiO2 photocatalyst using intense ultrashort titanium sapphire laser was investigated experimentally and theoretically aiming at the enhancement of photocatalytic reaction. The black surfacing of the TiO2 photocatalyst crystal was successfully achieved by drilling a large number of conical microholes with two-photon laser ablation. The ablated surface has a roughness of submicrometer order, and no heat-affected zone was observed. The simple equation is developed to explain two-photon ablation process of the TiO2 photocatalyst and the dependence of the ablation characteristic on the pulse duration. A maximization procedure of the ablated surface area is achieved and the optimization of laser parameters is shown for dense integration of ablated conical holes to increase the surface area. (C) 2000 American Institute of Physics. [S0021-8979(00)05204-X].