Dynamic optical properties of collagen-based tissue during ArF excimer laser ablation

Various attenuation mechanisms affecting the absorption of ArF excimer laser light in collagenous tissues have been studied. Temporal distortion of the laser pulse reflected from the cornea has been observed over a range of incident pulse fluences including the ablation threshold. Reflected pulse shortening begins near the ablation threshold and advances with increasing fluence. The measurement of laser light scattered 30 degrees off specular axis from collagen gel targets indicates that the reflected-pulse distortion is partially a result of scattering. Collagen film transmission studies show an increase in 193-nm light transmission in ablation conditions. These nonlinear attenuation mechanisms may impact significantly on the photoablation process.