Photodisruption in turbid tissue with 100-fs and 200-ps laser pulses

We compare the potential of 100-fs and 200-ps laser pulses for photodisruptive surgery on the surface and in the bulk of turbid tissue. Water, human epidermis cultures, and pig skin were used as tissue models. In our technique, tightly-focused femtosecond and picosecond laser pulses are nonlinearly absorbed, vaporizing tissue in the focal volume. We find that there are several advantages in using femtosecond pulses for photodisruption. The breakdown threshold is lower and the energy deposition is more deterministic for 100-fs pulses compared to 200-ps pulses. In human skin culture we observe photodisruption of tissue both on the surface and in the bulk using either 100-fs or 200-ps laser pulses. While both pulse widths produce surface and bulk photodisruption, there is significantly less collateral tissue damage for the femtosecond pulses, allowing for surgical precision at the cellular level. Preliminary results using pig skin as a more realistic model for live human skin will also be presented.