Ultrafast and precision drilling of glass by selective absorption of fiber-laser pulse into femtosecond-laser-induced filament

Abstract

The extremely intense light emitted from femtosecond laser pulses enables micro-drilling of glass. However, there are problems in femtosecond laser drilling, including low drilling speed and the damage during drilling. Because the volume removed by one femtosecond laser pulse is too small, hundreds of pulses must be focused on a single spot to create a hole with a diameter of 10 μm and a depth of over 100 μm. Furthermore, strong stress waves generated during the processing cause damage around the hole. In our research, we achieved ultrafast and precision drilling by coaxially focusing a single femtosecond laser pulse and a fiber laser pulse, with a wavelength that is transparent to the glass. A hole with a diameter of 10 μm and a depth of 133 μm was created in 40 μs, which indicates that the drilling speed was over 5000 times faster than that of conventional femtosecond laser drilling. By investigating the phenomena occurring after laser irradiation, we demonstrated that ultrafast drilling occurred because the fiber laser pulse was selectively absorbed by a high-aspect-ratio filament induced by the femtosecond laser pulse. Moreover, damage generation was inhibited because the material was thermally removed. The results help expand the range of applications for femtosecond laser processing in industry.

Nanoscale confinement of energy deposition in glass by double ultrafast Bessel pulses

“…Noticeably, the marks of thermal effects are highly reduced on the optical microscopy images and on the SEM images of Figure 1(b) in comparison with what is conventionally observed with picosecond illumination in glass [33] or in sapphire [31], or in comparison with illumination via a second pulse with nanosecond duration or more [34,35]. We infer that the thermodynamical pathways (ionization dynamics, pressure, temperature and so on) are different between the case of double femtosecond pulses excitation and the case of illumination by picosecond pulses.…”

Single‐Shot Reconfigurable Femtosecond Imaging of Ultrafast Optical Dynamics

“…Laser-induced filaments inside dielectric media have been an attractive topic in physics over the past couple of decades. [37] Extensive research has investigated the mechanisms of this nonlinear light-matter interaction, [37,38] and filaments have been ex-plored as promising candidates for use in 3D microfabrication [39] in photonics and microfluidics. Here, we switched CUSP to the 80-Tfps imaging mode (at the boundary between fragmented and continuous observations) and recorded the formation and propagation of a filament, which was generated by focusing a single femtosecond pulse (the pump), linearly polarized in the y direction, into a clean 1 mm thick glass slide at an oblique angle of 38°.…”

Analysis and mitigation of stress induced by rapid formation of through glass vias in thin substrates

“…[4][5][6] Laser wavelengths at which the glass substrate is transparent require a high intensity to induce multiphoton absorption, which is usually achieved, when using a single laser source, through short pulse duration. [7][8][9][10][11][12] Two laser sources, [13][14][15][16] or even tightly focused high energy ns laser pulses, 17 have also been employed to achieve intensities high enough to induce multiphoton absorption. Absorption can also be induced through the application of an absorber layer (such as with laser-induced wet/dry etching LIBWE/LIBDE methods 18 ), through doping the material 19 or by surface roughening.…”