Single pulse femtosecond laser damage in transparent dielectrics has been shown to occur through nonlinear
damage mechanisms that can allow material removal on scales well below the classical limit of the order of
the wavelength of the incident light. These mechanisms can be harnessed to allow the optical machining of
devices on the nanoscale.
We observe the formation of high aspect-ratio nanochannels by single femtosecond pulses. These channels,
several microns in length, can be formed at the front or rear surface of a sample, corresponding to conditions
under which spherical aberration is expected and where it is minimized. The presence of similar channels at
both locations suggests that aberration does not play a critical role in nanochannel creation, and we present
evidence supporting a dominant role of self focusing and microscale filamentation.
Applications for these long nanoscale diameter channels include nanopores, nanowells, or out-of-plane vias.
The ability to generate these channels with single pulses allows rapid fabrication that complements existing
techniques, thus addressing a major limitation to fabrication of microfluidics and nanopores.
The nonlinear mechanisms of femtosecond laser damage allow tight control of ablation to
precisely remove very small amounts of material, leaving holes as small as tens of nanometers
wide. By serially targeting laser pulses in glass, a host of three dimensional nano- and
microfluidic structures can be formed including nozzles, mixers, and separation columns.
Recent advances allow the formation of high aspect ratio nanochannels from single pulses, thus
helping address fabrication speed limitations presented by serial processing. Femtosecond
nanomachining is enabling for a variety of applications including nanoscale devices for analytic
separations, chemical analysis, and biomedical diagnostics.
We observe a discontinuity in the scaling between the size of damage and the pulse energy for
femtosecond laser pulses tightly focused at a glass surface. This discontinuity corresponds to the
threshold for formation and ejection of rings of material surrounding the focus center. The mechanism
for the generation of these structures appears distinct from that of the central holes and is ascribed to
subsurface absorption leading to thermal expansion and shock wave formation.