Diode laser using high power showed strong cutting ability for the soft tissue. Diode laser also showed biomodulation ability, which increases tissue healing or decreases inflammation under different lower power settings known as low-level laser therapy, LLLT. Diode lasers with 810nm wavelength show higher penetration on soft tissue and higher absorption in hemoglobin. However, the power penetration or absorption ability of a diode laser with 810nm wavelength in different colors and specimens is still unclear. The aim of this study was to evaluate the penetration ability of a diode laser with wavelength 810 nm in different colors of water and different solid materials using a power meter.
The 1.0-Watt (W) power of a diode laser with a tip diameter of 600μm to observe the power changes using a power meter was applied. The different laser irradiation distances 1.0cm, 5.0cm, and 10cm were set. Also, different thickness of the specimens was gradually increased to evaluate the power penetration ability of the diode laser. Water without color was used as a control group, while water with different colors (red, blue, royal blue, yellow, black, and green) as the experimental group. Single color and different variations of colors combination were evaluated. Nikon SMZ800N microscope was used to focus the color of specimens to determine the RGB value of color. FLIR thermal imaging camera measured surface temperature following laser irradiation for all liquid specimens. In addition, four different solid materials, including beef meat, wood, hard paper, and dry leather were used to evaluate the laser power penetration ability.
In terms of laser irradiation distance, laser powers decreased with increasing distance. A significant decreased (p < 0.05) in the penetration power on blue, royal blue, and black color specimens compared to control group. The red and yellow color specimens showed no significant difference. Royal blue showed no significant difference in laser penetration power and different laser irradiation distances. However, it showed a significant difference in penetration power between different specimen thicknesses. Two plates combined to create red color showed higher power penetration, while the royal blue color showed less power penetration. Luminance values of color were strongly correlated with laser power penetration. Laser penetration power increases exponentially with increased color luminance. Surface temperature following laser irradiation of different liquid specimens strongly correlated with laser power penetration. The royal blue showed significant differences (p < 0.05) in surface temperature compared to control and other colors. The correlation trendline shows the decreasing penetration power with increasing surface temperature. In the solid specimens, the mean value of laser penetration powers was negligible for wood, hard paper, and dry leather, while its higher for beef meat only and showing the same tendency for all the material thickness. The laser powers showed decreasing with the increase in laser distance, although the differences are insignificant for solid specimens.

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