Research On Etching Of Subwavelength Periodic Stripes By Using A Nanosecond Laser Pulse On The Surface Of Silica Films

With the development of miniaturized devices, nano-fabrication technique has been widely used. Traditional manufacturing techniques for micromachined photonics technology cannot meet the needs for further development. Laser-assisted nano-fabrication techniques attract much attention in its high precision, high processing speed, environmentally friendly, etc. With the advent of femtosecond laser, a spatial period which was significantly less than the laser wavelength appeared at the center of the damage spots. Achieved nano-micro devices getting smaller and smaller. But there were a plenty of studies shown that subwavelengths were limited in femtosecond and picosecond, nanosecond laser ablation were priority to etching, subwavelength stripes cannot be formed. Recently, studies have found that nanosecond laser irradiation can also form subwavelength stripes. This finding makes much progress in manufacturing nano-micro laser devices. Meanwhile, it is also a reference to the practical production and application of current research and nano-micro devices.This paper is a further study of predecessors. Sol-gel method and vertical deposition method were prepared in depositing SiO2particle films. Researched membrane structures by changing the amount of ammonia and water and N,N-dimethylformamide (DMF). These films were then irradiated using ND:YAG laser system, the laser wavelength was1064nm and pulse width was12ns, etching process was in a plurality of energy density, laser incident angle was0degree, only one laser pulse was imposed on the etching point. And summarized the relationship between membrane structure, the nanosecond laser parameters and subwavelength stripes.Researches found that with the increasing of ammonia and water, the size of SiO2increased. But the sol was not immobile when SiO2particle sizes increased enough, then it was not suitable for dip-coating. Adding N,N-dimethylformamide (DMF) as modifier, it could provent membrane layer from cracking, but the particle size decreased, and the structure became inordinance. It was not suitable for the nanosecond laser etching subwavelength experiments, so DMF was not used. At a wavelength of1064nm, pulse width of12ns, the stripes mainly appeared at the center of the damage spots, and these stripes spatial period were approximately0.5λ. These periodic stripes had the same spatial period, which was significantly less than the laser wavelength. Moreover, the periodic stripes were perpendicular to the direction of polarization of the laser irradiation and similarity to nanograting structures. A wide range of pulse fluence was suitable in forming subwavelength periodic stripes and higher pulse fluence results in a larger stripe spatial period. However, the relationship between the stripe spatial period and the particle size was not clear.