Beam propagation measurements of holmium laser radiation in biological tissue

摘要

Abstract: Although the light distribution during Holmium laser ablation of biological tissue is dominated by absorption like in homogeneous optically uniform media, indications exist that light scattering and thermal lensing also have considerable influence on the light distribution in tissue. These mechanisms influence the ablation threshold and the lateral extent of thermally altered tissue. With a fast temperature measurement technique we are able to measure the spatial beam profile before and after traversing a water layer or a tissue sample of defined thickness. the experiments were done with a free running Ho:YAG laser. The radiation was delivered through a single mode fiber in order to receive a well defined and reproducible laser beam. First results show a broadening of the laser beam after penetration of the sample relative to the incident beam, indicating light scattering and thermal lensing. !19