Photoluminescence and absorption in multi-energy Ge implanted type III silica

Silica samples were implanted at multiple energies with Ge ions, which resulted in an implanted layer, ∼2.4 μm in length starting ∼0.8 μm below the surface and in which the atomic percent of Ge ranged from ∼0.02% to ∼0.1%. Optical absorption was measured from 2.7 to 6.4 eV and in all spectra a local maximum at 5.0 eV and a shoulder at 5.9 eV were observed. Based on the bands reported in the literature we assumed that Gaussian bands at 4.8, 5.01, 5.17, 5.88, and a band greater than 6 eV determined by the fitting process comprised the observed spectra. Using Gaussian functions as basis states, fits to the data were performed yielding amplitudes for each band. An additional band at 5.54 eV was required to fit the spectra. This band’s amplitudes were correlated with the Ge concentration. Photoluminescence (PL) measurements were made from 2.6 to 4.6 eV using excitation energies from 4.5 to 5.5 eV. PL bands at ∼4.4 eV and ∼3.2 eV were detected. The 4.4 eV band intensity has a correlation coefficient of ∼1 with Si concentration. The band at 3.2 eV has a correlation coefficient ∼1 with the concentration of Ge ions. A PL band at 2.7 eV was not detected in either the Si or Ge implanted samples.