Synthesis of silica glass fibers and nanoparticles by continuous-wave laser backside irradiation

Abstract

We have developed a novel method to synthesize fibers and nanoparticles of silica glass using a continuous-wave laser. The synthesis process operates through continuous-wave laser backside irradiation (CW-LBI) of a glass substrate. In CW-LBI, a spindle-shaped emission is generated in the glass bulk along the optical axis; the emission propagates toward the light source as a confined plasma. The emission and its surroundings contain vaporized and molten glass. When the laser irradiation continues for a sufficient duration, the emission forefront reaches the glass surface, at which point vaporized and molten glass are ejected explosively. The ejected glass forms fibers and nanoparticles. Some of the nanoparticles become attached to the fiber surfaces during the explosion. The fiber diameters range from hundreds of nanometers to more than 10 μm. The particles on the fiber surfaces have diameters of tens of nanometers. A spindle-shaped hole remained in the glass substrate after the ejection, which had a depth of ~3.8 mm. This result indicated that the ejected materials originated from deep inside the glass bulk. High-speed camera observations of the ejection process and scanning electron microscopy of the ejected materials indicated that the fibers formed from the extraction from molten silica glass and particles formed by aggregation of vaporized silica glass.