To date, lasers have not succeeded in replacing mechanical tools in many hard tissue applications. Slow material removal rates and unacceptable collateral damage has prevented such a successful transition. Ultrashort pulses (<10 ps) have been shown to generate little thermal or mechanical damage. Recent developments now enable such short-pulse/high-energy laser systems to operate at high pulse repetition rates (PRR's). Using proper operating parameters, ultrashort pulse lasers (USPL's) could exceed the performance of conventional tissue processing tools and yield significant material volume removal while maintaining their minimal collateral damage advantages. As such, for the first time, USPL's offer real possibility for practical replacement of the air-turbine dental drill or other mechanical means for cutting hard tissues. In this study, the subpicosecond interaction regime was investigated and compared to nanosecond ablation by using a Titanium:Sapphire Chirped Pulse Amplifier (CPA) system with 1.05-m pulses of variable duration. Both 350fs and 1-ns pulse regimes were studied. Ablation rates (AR's), ablation efficiency, and surface characteristics revealed through electron micrographs were investigated. The study characterized the interaction with a variety of hard tissue types including nail, midear bone, dentin, and enamel. With 350-fs pulses, tissue type comparison showed a remarkably similar pattern of ablation rate and surface characteristics. Negligible collateral damage and highly efficient per-pulse ablation were observed in this pulse regime. These observations should be contrasted with the 1-ns pulse ablation characteristics where strong dependence on tissue type was demonstrated and ablation efficiency was approximately an order of magnitude smaller. With efficient interaction which minimizes collateral damage, and with both cost and size of ultrashort pulse systems decreasing, the implications of this study are far-reaching for the efficient use of USPL's in several fields of medicine that currently apply traditional surgical methods.

Plasma-mediated ablation makes use of high energy laser pulses to ionize molecules within the first few femtoseconds of the pulse. This process leads to a submicrometer-sized bubble of plasma that can ablate tissue with negligible heat transfer and collateral damage to neighboring tissue. We review the physics of plasma-mediated ablation and its use as a tool to generate targeted insults at the subcellular level to neurons and blood vessels deep within nervous tissue. Illustrative examples from axon regeneration and microvascular research illustrate the utility of this tool. We further discuss the use of ablation as an integral part of automated histology.The classic application of light microscopy to studies in physiology is observational; the illumination is too weak to affect the preparation. Yet the focused illumination in light microscopy can be strong enough to influence the chemical and physical structure of the sample and thus constitutes a means to manipulate living preparations. At the level of molecular studies, optical tweezers allow the application of forces and torques to individual molecules attached to dielectric microspheres [1,2]. At the level of subcellular organelles, photo-switching of fluorescent labels can toggle molecules between active and inactive states [3,4], while photo-activation of ions and small molecules provide a means to alter the chemical milieu within diffraction-limited volumes [5]. At the level of cells, photoswitching of bound ligands can lead to agonist binding [6], while light-activated membrane channels and pumps provide a means to change the electrical potential across cell membranes [7] Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. [8,9]. This last application is the subject of this review. NIH Public Access Principles and practice of plasma-mediated ablationPulsed laser systems easily achieve the high instantaneous peak powers necessary to induce nonlinear absorption, while maintaining sufficiently low average powers to avoid linear heating of the sample. This enables nonlinear imaging of biological structure and function [10], including two-photon laser scanning microscopy [11][12][13], second [14][15][16] and third harmonic [17][18][19][20][21][22] imaging, and coherent anti-stokes Raman spectroscopy [23,24]. The critical issue, especially for in vivo imaging, is that the nonlinear absorption allows excitation to occur only in the focus volume so that all excited molecules are a potential source of signal. Thus optical sectioning is performed solely by the excitation beam. Fluorescently labeled cells deep below th...

The use of an inexpensive diode laser can significantly enhance the delivery of topically applied glycerol for optical skin clearing. The laser use involves application of an absorption substrate onto the skin surface. Using carbon paper left no unwanted residue behind and is considered optimal for this purpose.

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