Burst-mode ultrafast laser treatments in biological tissues or in materials-processing use high-repetition-rate (⪆MHz) delivery of femtosecond laser pulses. This takes advantage of characteristically tiny residual heat left in a substrate through individual femtosecond-laser-matter interaction. At the same time, the approach opens the door to manipulating the accumulation of that same tiny heat during rapid pulse-repetition. This mode of fluence-delivery may, for instance, be able to denature the protein in the walls of a laser-cut wound and possibly improve infection rates in ultrashort-pulse laser surgery in certain contexts. Isolated intense sub-picosecond laser pulses typically do not rely on intrinsic chromophores for absorption, instead they first create a limited plasma via nonlinear ionization, then increase that plasma through collisional ionization. Used in burst-mode, plasma-mediated ablation can exploit some residual ionization which persists for a few nanoseconds, meaning that subsequent pulses need not re-initiate dielectric breakdown. In effect, the plasma is ‘simmered’ continuously throughout a burst, controlling the mode and amount of absorption and opening the door to particularly gentle laser cutting of tissues and dielectric materials. We describe pulse-by-pulse studies of the persistence of the plasma state within a burst of approximately 60 pulses, each of 300 fs duration, arriving with an intra-burst repetition rate of 200 MHz (5 ns separation). We also present the impact of these burst-mode treatments on cellular necrosis in a phantom of rat-glioma cells suspended in hydrogels and in porcine cartilage samples.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.