Figure 1.

Photoluminescence spectra. Photoluminescence spectra of the sample detected for as-grown and annealed samples in (a) visible spectral range (500 to 950 nm) and (b) infrared spectral range (1.4 to 1.6 μm). The experiments have been carried out using the 476.5-nm wavelength (nonresonant excitation for Er³⁺ ions).