The total hemispherical reflectivity R(A) and transmission T(A) for single-layer on glass samples show a quasi-zero absorption of the films, confirming the previous results from laser reflectometry and spectroscopic ellipsometry methods. The theoretical curves of Figs. 2 and 3 are calculated using the experimental optical constants determined by spectroscopic ellipsometry on single-layer samples. In our model, we suppose homogenous layers and sharp interfaces.

Figure 2 represents the total hemispherical reflectivity of Ti02/Si02 multilayers formed by three and five alternating layers of Ti02/Si02. The thicknesses of the layers are indicated in table 2. We observe a reflectivity peak in the visible range. The peak position determines the color of the multilayer film. The dotted lines indicate the theoretical reflectivity. We observe a good agreement between the experimental and the theoretical values. The reflectivity peak position, its maximum value and its FWHM depend on the layer thicknesses and on the number of layers. In general, at one wavelength the reflectivity peak maximum increases with increasing layer number.

Figure 3 shows the total hemispherical reflectivity of Al203/Si02 multilayers formed by an increasing number of alternating layers having the same thicknesses. The dotted lines indicate the theoretical reflectivity increasing with the layer number. This evolution shows the same tendency as previously presented results obtained by using the simplified model of constant refractive indexes [17].

The thicknesses of the individual layers of Fig. 3 are indicated in table 3. The peak position is relatively constant and its maximum value increases by increasing the number of alternating layers. The disagreement between the experimental and calculated values for

the nine-layers samples can be explained by the long deposition time and an eventual change of the deposition conditions.

Wavelength [nm]