NIR luminescent Er~(3+)/Yb~(3+) co-doped SiO_2-ZrO_2 nanostructured planar and channel waveguides: Optical and structural properties

摘要

Optical and structural properties of planar and channel waveguides based on sol-gel Er~(3+) and Yb~(3+) co-doped SiO_2-ZrO_2 are reported. Microstructured channels with high homogeneous surface profile were written onto the surface of multilayered densified films deposited on SiO_2/Si substrates by a femtosecond laser etching technique. The densification of the planar waveguides was evaluated from changes in the refractive index and thickness, with full densification being achieved at 900 ℃ after annealing from 23 up to 500 min, depending on the ZrO_2 content. Crystal nucleation and growth took place together with densification, thereby producing transparent glass ceramic planar waveguides containing rare earth-doped ZrO_2 nanocrystals dispersed in a silica-based glassy host. Low roughness and crack-free surface as well as high confinement coefficient were achieved for all the compositions. Enhanced NIR luminescence of the Er~(3+) ions was observed for the Yb~(3+)-codoped planar waveguides, denoting an efficient energy transfer from the Yb~(3+) to the Er~(3+) ion.