Ablation cooled material removal with bursts of ultrafast pulses
Author
Kerse, M. Can
Advisor
İlday, F. Ömer
Date
2016-01Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
Material processing with femto-second pulses allows precise and non-thermal material
removal and being widely used in scientific, medical and industrial applications.
However, due to low ablation speed at which material can be removed and
the complexity of the associated laser technology, where the complexity arises
from the need to overcome the high laser induced optical breakdown threshold
for e cient ablation, its potential is limited. Physics of the interaction regime
hinders a straightforward scaling up of the removal rate by using more powerful
lasers due to e ects such as plasma shielding, saturation or collateral damage
due to heat accumulation. In analogy to a technique routinely used for atmospheric
re-entry of space shuttles since 1950s, ablation cooling, is exploited here
to circumvent this limitation, where rapid successions of pulses repeated at ultrahigh
repetition rates were applied from custom developed lasers to ablate the
target material before the residual heat deposited by previous pulses di use away
from the interaction region. This constitutes a new, physically unrecognized and
even unexplored regime of laser- material interactions, where heat removal due to
ablation is comparable to heat conduction. Proof-of-principle experiments were
conducted on a broad range of targets including copper, silicon, thermoelectric
couplers, PZT ceramic, agar gel, soft tissue and hard tissue, where they demonstrate
reduction of required pulse energies by three orders of magnitude, while
simultaneously increasing the ablation e ciency by an order of magnitude and
thermal- damage-free removal of brain tissue at 2 mm3/min and tooth at 3
mm3/min, an order-of-magnitude faster than previous results.
Keywords
Ablation coolingUtrafast material processing
Burst mode laser
Nonthermal ablation
Ultra-high repetition rate