Porcine skin damage thresholds and computational modeling of continuous-wave laser exposure at 1567 nm

Continued development of high-power laser technology necessitates a robust framework for ensuring safe operation and hazard assessment. Many laser systems pertinent to atmospheric propagation applications operate in the infrared region where the potential for damage to the skin becomes similar in magnitude to that of the eye. This study investigated minimum visible lesion (MVL) damage thresholds for skin to 1567 nm laser exposure in Yucatan mini pig subjects, for exposure durations between 0.01 and 10 s, at Gaussian beam diameters of 0.63, 1.05, and 1.8 cm (1/e2). MVL thresholds, expressed as ED50 values, were compared to the maximum permissible exposure (MPE) limits as defined by the ANSI Z136.1-2022 laser safety standard. The resulting safety factors of the tested parameters range from 10.3 to 31.0, demonstrating the adequacy of the MPE limits in protecting skin from 1567 nm laser exposure and even making a case for less restrictive definitions. Histological analysis of a limited subset of exposures implies that exposures at or slightly above the MVL threshold involve superficial dermis damage, with deep partial thickness burns occurring at approximately twice the MVL level of exposure. Additionally, computational models of laser skin interactions produced reasonable agreement with experiments, with an average absolute percent difference of 9.6% for peak temperature simulations and 13.3% for threshold power estimates, across all parameters. These results demonstrate a robust computational modeling framework for the simulation of 1567 nm laser exposure to skin.