Microfabrication of structures by laser light in metal-doped glasses

The direct laser recording of light structures on the surface and in the bulk of novel, metal-doped, glasses is demonstrated. We record both two- and three-dimensional light structures in these materials. The light structure is an intensity distribution of the laser light, which can take the form of a focused beam to form microlenses, a moving focused beam to draw lines of sub-micron width or an interference pattern to write periodic structures. Experiments were performed in glasses containing either Cu²⁺ or Ag⁺ ions in a sub-surface layer, which are reduced to Cu or Ag atoms via reduction in a hot hydrogen atmosphere. The materials were investigated using both cw and pulsed laser light over a wide range of pulse lengths and peak intensities and at various wavelengths from the UV to the IR. The recorded structures were characterized using optical microscopy, atomic force microscopy and light diffraction. The mechanisms responsible for the sensitivity of the glass to laser radiation have been investigated both theoretically and experimentally. We have been able to demonstrate and control how the light is absorbed by the nanoparticles in the glass, how the temperature of the nanoparticles varies as a function of cluster size, laser wavelength and pulse duration, and how the glass matrix is effected by the laser energy absorbed in the randomly distributed clusters. For the glasses we have studied, the absorbed light results in local melting of the glass surrounding the nanoparticle which then leads to mass transfer and heat transfer kinetics in the material. This in turn leads to cluster aggregation and motion and allows the recording of the intensity pattern in the light. The growth of the clusters and their coalescence and motion has been measured.