Ultrafast laser micro-nano structuring of transparent materials with high aspect ratio

Ultrafast lasers are ideal tools to process transparent materials because they spatially confine the deposition of laser energy within the material's bulk via nonlinear photoionization processes. Nonlinear propagation and filamentation were initially regarded as deleterious effects. But in the last decade, they turned out to be benefits to control energy deposition over long distances. These effects create very high aspect ratio structures which have found a number of important applications, particularly for glass separation with non-ablative techniques. This chapter reviews the developments of in-volume ultrafast laser processing of transparent materials. We discuss the basic physics of the processes, characterization means, filamentation of Gaussian and Bessel beams and provide an overview of present applications

Exploring the ultrashort pulse laser parameter space for membrane permeabilisation in mammalian cells.

The use of ultrashort femtosecond pulsed lasers to effect membrane permeabilisation and initiate both optoinjection and transfection of cells has recently seen immense interest. We investigate femtosecond laser-induced membrane permeabilisation in mammalian cells as a function of pulse duration, pulse energy and number of pulses, by quantifying the efficiency of optoinjection for these parameters. Depending on pulse duration and pulse energy we identify two distinct membrane permeabilisation regimes. In the first regime a nonlinear dependence of order 3.4-9.6 is exhibited below a threshold peak power of at least 6 kW. Above this threshold peak power, the nonlinear dependence is saturated resulting in linear behaviour. This indicates that the membrane permeabilisation mechanism requires efficient multiphoton absorption to produce free electrons but once this process saturates, linear absorption dominates. Our experimental findings support a previously proposed theoretical model and provide a step towards the optimisation of laser-mediated gene delivery into mammalian cells.Publisher PDFPeer reviewe

Enhanced optical micromanipulation and transfection of cells using femtosecond lasers

This work investigates the use of continuous-wave and femtosecond-pulsed modes of a laser to obtain different functionalities when interacting with living cells using a single, simple, optical setup. This study demonstrates that careful control of the laser source in both spatial and/or temporal aspects of the output beam can offer major advantages in enhanced functionality and ease of use of fs-optical transfection systems. The results of this study are applicable in systems where fs-lasers are being utilized in applications that rely on nonlinear effects

Enhanced operation of femtosecond lasers and applications in cell transfection

In this work we present a review and discussion on the enhancement of femtosecond (fs) laser for use within biophotonics with a particular focus on their use in optical transfection techniques. We describe the broad range of source options now available for the generation of femtosecond pulses before briefly reviewing the application of fs laser in optical transfection studies. We show that major performance enhancements may be obtained by optimising the spatial and temporal performance of the laser source before considering possible future directions in this fields. In relation to optical transfection we describe how such laser source initiate a multiphoton process to permeate the cell membrane in a transient fashion. We look at aspects of this technique including the ability to combine transfection of such transfection we explore the role of new sources and "nondiffracting" light fields. (C) 2008 by WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim</p