Alexei V. Lukashev

Interaction of 1540-nm laser radiation with skin (in vivo): morphological and histologic study

The skin response was studied for different radiant exposure of short and long laser pulses and reaction to multipulse action using Er-glass laser radiation. Lesion ranging from a mild erytherma to tissue coagulation were produced on porcine skin. Radiant exposure producing 50 percent probability of a particular grade of lesion were established. A dependence of ED50 of minimum erythema versus number of pulses and beam cross section were studied. Histological investigation of the damage zone was made for qualitative study of injured skin. The dose-response relationship for producing different grades of burns were determined for energy densities of single laser pulse within the range 0.5-35 J/cm2 and pulse duration 100 ns and 3 ms. The single pulse dose in a chain of repetitive pulses producing minimum erythema were determined for 2n(n equals 1-6) pulses. The minimum reaction of skin on laser irradiance were studied for different beam diameter. The reaction of skin in mostly considered as local super heating. The data obtained are adequate to update safety standards for cutaneous injury within these ranges of radiant exposure and beam spotsize.

Laser damage of skin by 1540-nm Er-glass laser radiation: impact on laser safety standards

The skin response was studied for different radiant exposure of short and long laser pulses and reaction to multipulse action using Er-glass laser radiation. Lesion ranging from a mild erythema to tissue coagulation were produced on porcine skin. Radiant exposure producing 50 percent probability of a particular grade of lesion were established. A dependence of ED50 of minimum erythema versus number of pulses and beam cross section were studied. The dose-response relationship for producing different grades of burns were determined for energy densities of single laser pulse within the range 0.5- 35 J/cm2 and pulse duration 100 ns and 3 ms. The single pulse dose in a chain of repetitive pluses producing minimum erythema were determined for 2n(n equals 1-6 pulses). The minimum reaction of skin on laser irradiance were studied for different beam diameter. The reaction of skin is mostly considered as local super heating. The data obtained are adequate to update safety standards for cutaneous injury within thee ranges of radiant exposure and beam spotsize.

Efficient flash lamp pumped YSGG:Cr:Yb:Ho laser at 3 micron

We demonstrated that flash lamp-pumped YSGG:Cr:Yb:Ho laser at 3 /spl mu/m is feasible for practical use both in free running and Q-switched modes. This laser has high amplification gain. An output energy of 62 mJ was obtained by amplification of 10 mJ laser pulse. With improved optical components we believe that a scaled up configuration of the master oscillator and single pass amplifier will achieve reliable lasing up to 100 mJ in TEM/sub 00/ mode. That would give this laser new possibilities for applications in IR nonlinear optics and medicine.

Q-switching in a Cr{sup 3+}:Yb{sup 3+}:Ho{sup 3+}:YSGG crystal laser based on the {sup 5}I{sub 6} - {sup 5}I{sub 7} ({lambda}=2.92{mu}m) transition

An investigation was made of the generation of giant pulses in a new yttrium scandium gallium garnet laser crystal doped with holmium (Cr3+:Yb3+:Ho3+:YSGG) operating on the basis of the self-terminating 5I6 — 5I7 transition. Q-switching was performed by an electro-optical lithium niobate switch, a passive switch based on an epitaxial film of indium arsenide on a gallium arsenide substrate, or a passive switch consisting of water. The 2.92 μm wavelength dominated giant pulse generation, whereas under free-running conditions the radiation was discretely tunable in the range 2.84 —3.05 μm. Depending on the Q-switching method, pulses of 60 — 160 ns duration were generated and the pulse energy was ~20 mJ. The second and fourth harmonics of the holmium laser radiation were generated and the efficiency of each frequency-multiplication stage was ~20%.An investigation was made of the generation of giant pulses in a new yttrium scandium gallium garnet laser crystal doped with holmium (Cr{sup 3+}:Yb{sup 3+}:Ho{sup 3+}:YSGG) operating on the basis of the self-terminating {sup 5}I{sub 6} - {sup 5}I{sub 7} transition. Q-switching was performed by an electro-optical lithium niobate switch, a passive switch based on an epitaxial film of indium arsenide on a gallium arsenide substrate, or a passive switch consisting of water. The 2.92 {mu}m wavelength dominated giant pulse generation, whereas under free-running conditions the radiation was discretely tunable in the range 2.84 -3.05 {mu}m. Depending on the Q-switching method, pulses of 60 - 160 ns duration were generated and the pulse energy was {approx}20 mJ. The second and fourth harmonics of the holmium laser radiation were generated and the efficiency of each frequency-multiplication stage was {approx}20%. (lasers)

Morphological and histological changes on skin induced by 1540-nm laser radiation

The dose-response relationship for producing different grades of burns on skin produced by single Er-glass laser pulse were determined for energy densities within the range 0.5-35 J/cm2 and pulse duration 100 ns and 2.5 ms. The persistent lesions on skin were subdivided into four morphologically different groups vs. radiant exposure of laser pulses. Histological investigation were made at 1- and 3-days post-exposure. Different methods of tissue preparation were tried to obtain better contrast of laser induced changes in skin tissue. At the 1-day post-exposure we observed on the histological samples coagulation of surface tissue, epidermis and dermis of skin depending on radiant exposure. 3-days histological samples revealed tearing of tissue detrit and active epitalization of damaged tissue.

Laser safety standard for skin at 1540 nm: new experiment and estimations

Radiant exposure of an Er-glass laser producing 50 percent probability (ED50) of a minimum erythema on porcine skin was measured in vivo for laser pulses 100 ns and 2.5 ms pulse duration. ED50 at 24 hours post-exposure was found 3.5 J/cm2 for short laser pulses and 6.5 J/cm2 for long ones. The single pulse dose in a chain of repetitive pulses producing minimum erythema were determined for 2n(n equals 16) pulses. The minimum reaction of skin on laser irradiance were studied for different beam diameter. The reaction of skin is mostly considered as local super heating. THe data obtained in the study are adequate to update safety standards for cutaneous injury.