Photodisruption in turbid tissues with ultrashort laser pulses

We investigate the potential of femtosecond laser pulses for photodusruptive surgery on the surface and in the bulk of turbid tissue. Human epidermis cultures, mouse skin, and pig skin were used as tissue models. We use nonlinear absorption of tightly focused 100-fs laser pulses to vaporize tissue in the focal volume. By focusing the pulse in the bulk of the skin, we can vaporize 10-µm diameter regions up to 100 µm beneath the surface with minimal damage to the surrounding tissue. This technique offers exciting possibilities for clinical dermatology applications, such as tattoo removal and skin resurfacing. The small scale of the photodisruption also opens the door to single cell and sub-cellular photodisruption for biological research. We also demonstrate that femtosecond laser pulses are ideal for making precise incisions in the skin of about 50 µm in depth and only 5-µm width. In addition to providing an extremely sharp scalpel, this technique may be useful for enhancing transdermal drug delivery. Finally, we have investigated the role self-focusing plays in short-pulse photodisruption of tissue. The potential for real world clinical and research applications of our work will be discussed, as well as the importance of using pulses of femtosecond duration.