Figure 10.

Ratios of layer refractive index after and before the Er doping. For 1.25- (a) and 10-μm-thick (b) PSi samples. The ratios (large blue dots with error bars) are obtained by dividing the 2 nL values obtained after and before the Er doping from the reflectivity spectra as described in the text. The observed behavior for high and low doping is coherent with the doping threshold discussed earlier.