Neutral density (ND) filters are frequently used to vary radiant energy and irradiance in laser-tissue interactions. In the
process of preparing an optical train for exposure of tissue to near infrared laser exposure, the absorbance of various ND
filters was examined. ND filters were characterized for transmittance between 500 and 2000 nanometers using a
CARY-500 spectrophotometer. By characterizing the optical transmittance of the ND filters we were able to accurately predict
their effect on the near infrared laser beam. The ND filters were also characterized before and after laser exposure to see
if any laser-induced changes in optical density occurred.