Numerical simulation of optical breakdown for cellular surgery at nanosecond to femtosecond time scales

Alfred Vogel; Joachim Noack

doi:10.1117/12.446504

26 October 2001 Numerical simulation of optical breakdown for cellular surgery at nanosecond to femtosecond time scales

Alfred Vogel, Joachim Noack

Proceedings Volume 4433, Laser-Tissue Interactions, Therapeutic Applications, and Photodynamic Therapy; (2001) https://doi.org/10.1117/12.446504
Event: European Conferences on Biomedical Optics, 2001, Munich, Germany

Abstract

We have shown by experimental investigations that cellular surgery (microdissection, optoporation, and optoinjection) with Nd:YAG laser pulses of 1064 nm and 532 nm wavelength relies on nonlinear absorption leading to optical breakdown and plasma formation at the laser focus. The present study explores possibilities of refining the breakdown effects by employing shorter pulse durations and irradiances that generate plasmas below the threshold for shock wave and bubble formation. Optical breakdown in water at NA = 0.9 and NA = 1.3 was simulated numerically for wavelengths of 1064 nm, 532 nm and 355 nm, and pulse durations of 6 ns, 30 ps and 100 fs. We used a rate equation model that allows the calculation of the temporal evolution of the free electron density r during breakdown. r (t) could be followed separately for the free electrons generated by multiphoton ionization and avalanche ionization. We obtained excellent agreement between the calculated and measured threshold values for breakdown with 6-ns pulses. The simulations predict that the energy threshold for cellular surgery can be reduced by a factor of 350-2600 (depending on wavelength) when the pulse duration is reduced from 6 ns to 100 fs. The calculated breakdown energies for 100 fs pulses focused by an objective with NA = 1.3 are 0.6 nJ at 355 nm, 1.6 nJ at 532 nm, and 3.9 nJ at 1064 nm. With ns-pulses at 1064 nm, the breakdown threshold is very sharp, i. e. there is either no effect at all, or a dense plasma is formed causing a micro-explosion. With shorter wavelengths and pulse durations, the threshold is smoother, and electron densities may be produced that stay below the threshold for explosive vaporization and bubble formation. This creates the possibility of achieving highly localized plasma-mediated chemical or thermal changes in the cell. We conclude that both the reduced energy threshold and the smoother breakdown process with fs pulses bear a large potential for the refinement of intracellular surgery.

Citation Download Citation

Alfred Vogel and Joachim Noack "Numerical simulation of optical breakdown for cellular surgery at nanosecond to femtosecond time scales", Proc. SPIE 4433, Laser-Tissue Interactions, Therapeutic Applications, and Photodynamic Therapy, (26 October 2001); https://doi.org/10.1117/12.446504

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

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.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available