Abstract

When laser cutting tissue a coagulated layer is formed along the incision walls. We studied its extension in freshly excised animal dermis cut by identical overlapping laser pulses of 250-μs duration at a repetition rate of 4 Hz. We compare the effect of a free running 2.94-μm Er³⁺ laser with a penetration depth d < 1 μm and a CO₂ laser with d ≈ 10 μm. If the cutting beams are focused to diameters smaller than half of a millimeter, the extensions of the resulting thermal alterations in tissue, being typically larger than 300 μm, depend more strongly on the focal geometry than on the optical penetration depth of the drilling beam. Tissue material is heated, liquefied, and partially ejected during laser cutting.

© 1989 Optical Society of America