Fabrication and optical optimization of spot-size converters with strong cladding layers

A silicon-on-insulator (SOI) optical fiber-to-waveguide spot-size converter (SSC) overlaid with specially treated silica is investigated for integrated optical circuits. Unlike the conventional process of simply depositing the hot silica on silicon waveguides, two successive layers of silicon dioxide were grown on etched SSC structures by PECVD (plasma-enhanced chemical vapor deposition). The two layers have 0.8% index contrast and supply stronger cladding for an incident light beam. Additionally, this process is able to reduce the effective refractive index of the input mode to less than 1.47 (extremely close to that of the fiber), substantially weakening the unwanted back reflection. Exploiting this technology, it was demonstrated that the SSC showed a theoretical low mode mismatch loss of 1.23 dB for a TE-like mode and has an experimental coupling efficiency of 66%.

The transition from Eu3+ to Eu2+ in SiO2(Eu) thin films prepared by ion implantation and co-sputtering

Eu ions doped SiO2 thin films, SiO2( Eu), were prepared by co-sputtering of SiO2 and Eu2O3 and Eu ion implantation into thermally grown SiO2 films. The Eu-L-3-edge X-ray absorption near edge structure (XANES) spectra of SiO2(Eu) films show a doublet absorption peak structure with energy difference of 7 eV, which indicates the conversion of Eu3+ to Eu2+ at high annealing temperature in N-2. The strong blue luminescence of SiO2(Eu) films prepared by ions implantation after films annealed above 1100 degreesC confirms the above argument.