Origin of thermally activated Er3+ emission in GeGaSe films and waveguides.

The origin of the dead or active emission from Er in various Er-doped films has been unclear. Here we took Er-doped GeGaSe as examples and investigated the correlation between the intensity of the photoluminescence (PL) spectra, the content of the activated Er ions, and the intensity of the absorption spectra in the waveguides. We found the linear correlation between the content of Er ions, photoluminescence, and absorption intensity. This provides clear evidence that thermal annealing can promote the conversion of Er metals into Er ions, and such a conversion is essential for practical applications, in which the number of the activated Er ions rather than the nominal Er contents in the materials plays an important role in achieving emission and thus effective optical amplification and lasing.

Real-time change of optical losses in chalcogenide waveguides induced by light illumination.

We prepared several GeGaSe waveguides with different chemical compositions and measured the change of optical losses induced by light illumination. Together with some experimental data in As2S3 and GeAsSe waveguides, the results showed that maximum change of the optical loss can be observed in the waveguides under bandgap light illumination. The chalcogenide waveguides with close to stoichiometric compositions have less homopolar bonds and less sub-bandgap states, and thus are preferential to have less photoinduced losses.