PREDICTED TRENDS IN RETINAL DAMAGE THRESHOLDS FOR PULSE DURATIONS SHORTER THAN 50 FS AND IMPLICATIONS TO MAXIMUM PERMISSIBLE EXPOSURE LEVELS

摘要

Laser-induced breakdown has been implicated in the threshold for damage of the retina below 100 fs. Laser pulses shorter than 50 fs possess enough wavelength bandwidth that during propagation, the pulse can lengthen or shorten because of the differences in refractive indices for different wavelengths. This phenomenon is called group velocity dispersion (GVD). We have modeled the dependence of the laser-induced breakdown threshold propagation in the eye in the wavelength band relevant for retinal damage (400 - 1400 nm). These computations take into account both aberrations and GVD while allowing for changes in the input pulse chirp. The computations were performed on a Beowulf-class parallel computer cluster. The trends in retinal damage were predicted to determine if extension of the 1 ps to 100 fs maximum permissible exposure levels provide significant protection from lasers with these pulse durations.