Effect of Diode Laser Irradiation on Optical Properties of Methylene Blue Dye Solution


AbstractIn this study, the effect of the diode laser (λ=650nm) on the methylene blue (MB) dye solution with concentration (1×10-5 mole/liter) in distilled water was demonstrated. Three different powers (5,100 and 500) mW of diode laser as well as different irradiation times (7.5, 11.5, 15 and 16.5) hours were tested. The peak absorption wavelength of MB at 665 nm with intensity (0.853) was observed and this intensity decreased with increasing exposure time and laser power. The blue color of the MB dye becomes completely colorless after irradiation for 16.5 hours by laser power of 500 mW. The optical properties (Transmission (T) and Reflection (R) spectra, Refractive index (n), Absorption coefficient (α), Optical energy gap, Extinction Coefficient (k) and Dielectric Constants( εr, εi) were calculated. The decolorization mechanism for the sample was also discussed. The results showed that the increasing in power and time irradiation of diode laser led to decrease intensity of absorption spectrum.