Abstract
A series of experiments are conducted in vivo using Yucatan mini-pigs (Sus scrofa domestica) to determine thermal damage thresholds to the skin from 1940-nm continuous-wave thulium fiber laser irradiation. Experiments employ exposure durations from 10 ms to 10 s and beam diameters of approximately 4.8 to 18 mm. Thermal imagery data provide a time-dependent surface temperature response from the laser. A damage endpoint of minimally visible effect is employed to determine threshold for damage at 1 and 24 h postexposure. Predicted thermal response and damage thresholds are compared with a numerical model of optical-thermal interaction. Results are compared with current exposure limits for laser safety. It is concluded that exposure limits should be based on data representative of large-beam exposures, where effects of radial diffusion are minimized for longer-duration damage thresholds.
Highlights
Standardscommittees are currently pursuing revisions of laser safety standards
From the analysis presented here, the conclusion is that current exposure limits maintain the commonly accepted safety margins for lasers that can be developed in these infrared bands
Damage mechanisms at 2000 and 1940 nm in skin are not significantly different, as evidenced by the damage threshold levels reported here and by Chen et al.[3,4]. These differences in threshold level are consistent with current understanding as implemented in computational models of thermal damage
Summary
Standardscommittees are currently pursuing revisions of laser safety standards. Revisions are focused on the near-infrared region and are based primarily on new data collected within the wavelength region of 1100 to 1400 nm.[1]. Many laser systems employ high-power Ho:YAG and thulium fiber lasers. These lasers are being used in expanding ranges of application and may, in some cases, effectively replace CO2 lasers. As exposure limits for these near-2000-nm wavelengths were based on limited data, we have undertaken a series of experiments to add information for the current revision of safety standards. These will ensure that the use of new systems have appropriately validated exposure limits, based on experimentally observed and theoretically predicted mechanisms
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