## 3 Results and Discussions
### Parametric Analysis
#### 3.3.1 Effects of Laser Light Wavelength  
In the present work, only three different laser wavelengths (520, 785 and 840 nm) are considered. Table 1 shows the absorption coefficient, the scattering coefficient and the anisotropic factor of the human skin at 785 nm. Table 2 summarizes these properties at 520 and 840 nm. Additionally, three laser pulse widths (1, 10 and 25 ps) are analyzed.  
Figure 11: Effects of the scattering coefficient of the CM malignancy on the temporal reflectance signals.  
Figure 10: Effects of affected volumes on the temporal reflectance signals from the skin with CM malignancy.  
Figures 8 and 9 show the temporal transmittance and reflectance signals from normal skin subjected to a laser at these three different wavelengths and three laser pulse widths. The increase of the laser wavelength decreases the magnitudes of these two signals due to the decrease in the optical thickness of skin when the laser wavelength varies from \(\lambda\) = 840 nm to \(\lambda\) = 785 nm.  
In addition, laser diffuses to a greater distance at higher wavelengths at lower wavelengths, which can be shown in the difference in magnitude of the transmittance (Figure 8).  
In the case of the much smaller wavelength (\(\lambda\) = 520 nm), no transmittance signals appear at the boundary opposite to the laser source (i.e., the boundary at x = \(L_{\mathrm{x}}\) (Figure 8)). This is principally due to the attenuation of the light, which decreases with an increase of the laser wavelength, as shown in Tables 1 and 2. Furthermore, the human skin is optically thick at the smaller wavelength of \(\lambda\) = 520 nm, so no transmittance can reach the boundary opposite the laser source. On the other hand, the reflectance signals at x = 0, from the human skin subjected to laser light at the smaller wavelength of \(\lambda\) = 520 nm, display an augmentation in the peak magnitude in comparison to the larger wavelengths of 785 and 840 nm when the laser width is 1 ps (Figure 9). For small wavelengths, most of the scattered light at the skin-surface is reflected from the stratum comeum by the laser pulse below 6 ps. Therefore, the peak magnitude of the reflectance profiles of the smaller laser wavelength (\(\lambda\) = 520 nm) occurs before those at larger laser wavelengths (\(\lambda\) = 785 and 840 nm), as shown in Figure 8, although Figure 9 reveals that this trend in the reflectance signals is reversed for the laser pulse widths of 10 and 25 ps.  
The increase of the laser pulse width above 10 ps (i.e., for 10 and 25 ps) increases the peak magnitude of the reflectance signals at the larger wavelengths (\(\lambda\) = 785 and 840 nm), and these peaks become higher than the obtained value for the smaller laser wavelength (\(\lambda\) = 520 nm). The input heat and time for which the pulse persists at any position are increased when the pulse width is above 10 ps. Therefore, the effect of the highest radiation arriving at the laser-source border from the human skin layers with a pulse width greater than 10 ps. The higher wavelength limits the outcome of the important portion of the radiation reaching the laser-source boundary from the stratum comeum. However, for the case of \(\lambda\) = 520 nm, most of the light scatters from the stratum comeum, so the signals still seem ahead of those obtained for the two other higher wavelengths.