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.
Laser alignment thermal sensitive paper can be used for laser applications such as spot size measurements, beam
characteristics, and determining beam mode. Thermal sensitive paper interactions with a 1.54 micron, 35 ns, 3.75 J, Er-Glass laser produced spots that had three concentric zones of response. These spots interact with each other if a
minimum distance between exposures is not maintained. The distance needed between spots is directly related to the
energy density incident upon the paper. Although there was no lot designation for the box of thermal sensitive papers
used in this research, we were able to determine that the response of different papers in the same box could vary under
constant laser exposure parameters. Therefore, investigators need to be cautious when extrapolating experimental data
from exposures using this type of laser alignment paper.