Femtosecond laser microfabrication

S. K. Sundaram, C. B. Schaffer, and E. Mazur. 2003. “Microexplosions in Tellurite glasses.” Appl. Phys. A, 76, Pp. 379–384. Publisher's VersionAbstract
Femtosecond laser pulses were used to produce localized damage in the bulk and near the surface of baseline, Al2O3-doped, and La2O3-doped sodium tellurite glasses. Single or multiple laser pulses were nonlinearly absorbed in the focal volume by the glass, leading to permanent changes in the material at the focal volume. These changes are caused by an explosive expansion of the ionized material in the focal volume into the surrounding material, i.e., a microexplosion. Writing of simple structures (periodic array of voxels, as well as lines) was demonstrated. The regions of microexplosion and writing were characterized using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and atomic force microscopy (AFM) postmortem. Fingerprints of microexplosions (concentric lines within the region and a concentric ring outside the region), due to the shock wave generated during microexplosions, were evident. In the case of the baseline glass, no chemistry change was observed within the region of the microexplosion. However, Al2O3-doped and La2O3-doped glasses showed depletion of the dopant from the edge to the center of the region of the microexplosions, indicating chemistry gradient within the regions. Interrogation of the bulk- and laser-treated regions using micro- Raman spectroscopy revealed no structural change due to the microexplosions and writing within these glasses.
A. Ben-Yakar, A. Harkin, J. Ashmore, M. Shen, E. Mazur, R. L. Byer, and H.A. Stone. 2003. “Thermal and fluid processes of a thin melt zone during femtosecond laser ablation of glass.” In . Photon Processing in Microelectronics and Photonics II. Publisher's VersionAbstract
Microfluidic channels on borosilicate glass are machined using femtosecond lasers. The morphology of the ablated surface is studied using scanning microscopy. The results show micron scale features inside the channels. The formation mechanism of these features is investigated by additional experiments accompanied by a theoretical analysis of the thermal and fluid processes involved in the ultrafast laser ablation process. These studies indicate the existence of a very thin melting zone on glass and suggest that the surface morphology is formed by the plasma pressure-driven fluid motion of the melting zone during the ablation process.

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