Abstract
There is increasing use of mid-infrared optical parametric oscillator radiation operating in the wavelength range of 3-5 µm. To expand existing damage data for skin exposure to lasers in this wavelength region, the in-vivo damage threshold at the wavelength of 3.743 µm was determined in a Guizhou miniature pig model for an exposure duration of 1.0 s. The irradiance of the laser spot was nearly Gaussian-distributed and the 1/e2 beam diameter on the animal skin surface was fixed at 0.94 and 0.88 cm along horizontal and vertical directions. Damage lesion determinations were performed at 1- and 24-hour post-exposure. The probit analysis was employed to establish the ED50 values. The ED50 expressed in peak radiant exposure for the Gaussian spot was 4.04 J/cm2 at the 24-hour post-exposure. Sufficient margin existed between the damage threshold and MPE from the current laser safety standard. The obtained data may contribute to the knowledge base for refinement of laser safety standard in the wavelength range of 2.6-1000 µm.
Highlights
Laser systems operating in the wavelength range of 3–5 μm are in widespread use in military and scientific applications [1,2,3]
The exposure limits (ELs) for various wavelengths and pulse widths are defined by the International Commission on Non-Ionizing Radiation Protection [16], and maximum permissible exposures (MPEs) are specified in laser safety standards including IEC 60825-1 and ANSI Z136.1 [17,18]
We summarized laser-induced skin damage thresholds for the exposure duration of 1.0 s at diverse wavelengths including 1.06, 1.319, 2.0, 3.743 and 10.6 μm, as shown in Table 4 [19,25,26,32,33,34,35]
Summary
Laser systems operating in the wavelength range of 3–5 μm are in widespread use in military and scientific applications [1,2,3]. The maximum power of continual-wave infrared OPO laser has been increased above 30 W, with wavelength tuning range of 3.2–3.9 μm [15]. At the wavelength of 2.0 μm, Chen et al performed experimental and simulation studies to investigate skin damage effects for various exposure durations (0.25–2.5 s) and incident beam diameters (5–15 mm) [19,20,21]. At the wavelength of 1.94 μm, skin damage thresholds were determined by Oliver et al for exposure durations from 10 ms to 10 s and beam diameters of 4.8 to 18 mm [22]. At the wavelength of 1.54 μm, damage threshold measurements were performed by Cain et al for two exposure durations (600 μs and 31 ns) and three spot sizes (0.7, 1.0 and 5.0 mm) [23]. At the wavelength of 1070 nm, damage threshold measurements were performed by Vincelette et al for a range of beam diameters (0.6–9.5 cm) and exposure durations (0.01–10 s) [27], and DeLisi et al determined damage thresholds for multiple-pulsed laser exposures at a constant beam diameter of 1 cm [28]
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