We discuss the dynamics of ultrashort pulsed laser excitation in bulk optical silica-based glasses(fused silica and borosilicate BK7) well-above the permanent modification threshold. We indicate subsequent structural ...We discuss the dynamics of ultrashort pulsed laser excitation in bulk optical silica-based glasses(fused silica and borosilicate BK7) well-above the permanent modification threshold. We indicate subsequent structural and thermomechanical energy relaxation paths that translate into positive and negative refractive index changes, compression and rarefaction zones. If fast electronic decay occurs at low excitation levels in fused silica via self-trapping of excitons,for carrier densities in the vicinity of the critical value at the incident wavelength, persistent long-living absorptive states indicate the achievement of low viscosity matter states manifesting pressure relaxation, rarefaction, void opening and compaction in the neighboring domains. An intermediate ps-long excited carrier dynamics is observed for BK7 in the range corresponding to structural expansion and rarefaction. The amount of excitation and the strength of the subsequent hydrodynamic evolution is critically dependent on the pulse time envelope, indicative of potential optimization schemes.展开更多
Understanding material structural reaction to light is of utmost importance to advance processing resolution in ultrafast laser volume structuring into the nanoscale.Selective thermodynamic pathways are required to qu...Understanding material structural reaction to light is of utmost importance to advance processing resolution in ultrafast laser volume structuring into the nanoscale.Selective thermodynamic pathways are required to quench energy transport in the most rapid manner and to confine the process to nanometer lengths,bypassing optical resolution.Quantifying material dynamics under confinement,with in situ access to transient local temperature and density parameters,thus becomes key in understanding the process.We report in situ reconstruction of thermodynamic states over the entire matter relaxation path in bulkα-quartz irradiated by ultrafast nondiffractive laser beams using time-resolved qualitative and quantitative optical phase microscopy.Thermooptic dynamics indicate rapid spatially confined crystalline-to-amorphous transition to a hot dense fused silica form.Densification exceeds 20%and the matrix temperature rises to more than 2,000 K in the first nanosecond.This structural state relaxes in hundreds of nanoseconds.The dispersion and time design of the optical beam to picosecond durations increases the spatial confinement and triggers an extreme nanostructuring process based on nanocavitation that occurs within the amorphizing material,where the low-viscosity phase lowers the mechanical requirements for the process.Processing feature scales of less than a tenth of the optical wavelength are obtained in the volume.This allows for structural and morphological nanoscale material features under 3D confinement that can engineer optical materials.展开更多
基金support of the Agence Nationale de la Recherche(projects ANR 2011 BS04010 NanoFlam and ANR 2011 BS09026 SmartLasir)
文摘We discuss the dynamics of ultrashort pulsed laser excitation in bulk optical silica-based glasses(fused silica and borosilicate BK7) well-above the permanent modification threshold. We indicate subsequent structural and thermomechanical energy relaxation paths that translate into positive and negative refractive index changes, compression and rarefaction zones. If fast electronic decay occurs at low excitation levels in fused silica via self-trapping of excitons,for carrier densities in the vicinity of the critical value at the incident wavelength, persistent long-living absorptive states indicate the achievement of low viscosity matter states manifesting pressure relaxation, rarefaction, void opening and compaction in the neighboring domains. An intermediate ps-long excited carrier dynamics is observed for BK7 in the range corresponding to structural expansion and rarefaction. The amount of excitation and the strength of the subsequent hydrodynamic evolution is critically dependent on the pulse time envelope, indicative of potential optimization schemes.
基金funded by a public grant from the French National Research Agency(ANR)under the“France 2030”investment plan,with the reference EUR MANUTECH SLEIGHT-ANR-17-EURE-0026funded by the ANR grants ANR-19-CE30-0036 and ANR-21-CE08-0005support from the Jean Monnet University under its research supporting actions plan.Numerical calculations have been performed using HPC resources from GENCI-TGCC,CINES(Project gen7041)。
文摘Understanding material structural reaction to light is of utmost importance to advance processing resolution in ultrafast laser volume structuring into the nanoscale.Selective thermodynamic pathways are required to quench energy transport in the most rapid manner and to confine the process to nanometer lengths,bypassing optical resolution.Quantifying material dynamics under confinement,with in situ access to transient local temperature and density parameters,thus becomes key in understanding the process.We report in situ reconstruction of thermodynamic states over the entire matter relaxation path in bulkα-quartz irradiated by ultrafast nondiffractive laser beams using time-resolved qualitative and quantitative optical phase microscopy.Thermooptic dynamics indicate rapid spatially confined crystalline-to-amorphous transition to a hot dense fused silica form.Densification exceeds 20%and the matrix temperature rises to more than 2,000 K in the first nanosecond.This structural state relaxes in hundreds of nanoseconds.The dispersion and time design of the optical beam to picosecond durations increases the spatial confinement and triggers an extreme nanostructuring process based on nanocavitation that occurs within the amorphizing material,where the low-viscosity phase lowers the mechanical requirements for the process.Processing feature scales of less than a tenth of the optical wavelength are obtained in the volume.This allows for structural and morphological nanoscale material features under 3D confinement that can engineer optical materials.
