Preliminary results on the spectral dependence of the absorption of light in tissue are presented and discussed with respect to medical laser application.
Singlet decay times in dependence on temperature, concentration, solvent and detergent were measured in solutions of organic laser dyes. In the temperature range from 300 K to 115 K the reciprocal decay time obeys an Arrhenius relationship, the parameters of which were determined. Additional measurements were carried out on Acridinorange because a biexponential fluorescence decay due to monomers (τ = 4.2 ns) and aggregated molecules (τ = 14.7 ns) was found.
During irradiation with an Ar+-and Kr+-laser the temperature rise in living and dead tissue was measured in various depths. The contribution of the blood flow to the heat transport during irradiation was found to be small. The influence of the different depths of penetration and backscattering at the blue-green Ar+-and the red Kr+-radiation was investigated. The measurements compared with theory show reasonable agreement for an one-dimensional model below 100 degrees C. The results are discussed with respect to laser application in medicine.
A spatially periodic distribution of excited electronic states is produced in ruby which is placed into the interference region of two light beams derived from a pulsed laser (wavelength 530 nm). The spatially modulated population density acts like an optical grating and is detected by diffraction of a quasi‐cw laser beam (488 nm). The lifetimes of the population density gratings are measured for ruby crystals with 0.05 to 5% Cr‐doping and compared with the fluorescence lifetimes of the R‐lines (694 nm). For the 0.05% ruby both lifetimes are nearly equal. At higher Cr‐concentrations the grating decay is considerably faster than the fluorescent decay. The grating lifetimes are independent of the grating period A = 1 to 100 μm. From this observation an upper limit of the diffusion constant for energy transfer between excited electronic states in ruby is estimated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.