Infrared skin damage thresholds from 1940-nm continuous-wave laser exposures.

Area of Science:

• Biomedical Engineering
• Laser Physics
• Dermatology

Background:

• The 1940-nm thulium fiber laser is utilized in various applications, necessitating clear understanding of its thermal effects on biological tissues.
• Establishing accurate thermal damage thresholds is crucial for laser safety guidelines and preventing unintended tissue injury.

Purpose of the Study:

• To determine the in vivo thermal damage thresholds of Yucatan mini-pig skin exposed to 1940-nm continuous-wave thulium fiber laser irradiation.
• To compare experimental results with a numerical optical-thermal interaction model and current laser safety exposure limits.

Main Methods:

• In vivo experiments were conducted on Yucatan mini-pigs using a 1940-nm continuous-wave thulium fiber laser.
• Exposure durations ranged from 10 ms to 10 s with beam diameters from 4.8 to 18 mm.
• Thermal imagery captured surface temperature response, and a minimally visible effect endpoint defined damage thresholds at 1 and 24 hours postexposure.

Main Results:

• Experimental data on skin thermal response and damage thresholds were collected.
• A numerical model was used to predict thermal response and damage thresholds, showing good correlation with experimental findings.
• Results indicated that radial diffusion effects are minimized in larger beam exposures, particularly for longer durations.

Conclusions:

• Current laser safety exposure limits may require revision based on large-beam exposure data.
• For longer-duration damage thresholds, minimizing radial diffusion by using large-beam data is recommended.
• This research provides critical data for refining safety standards for thulium fiber laser applications on skin.