Efficient and thermally enhanced frequency upconversion in Yb3+-sensitized Tm3+-doped silica-on-silicon buried waveguides excited at 1.064 μm

Efficient and thermally enhanced frequency upconversion of cw infrared radiation at 1.064 μm into blue (480 nm), red (660 nm) and near-infrared (800 nm) light in integrated Tm 3+ /Yb 3+ -codoped phosphosilicate silica-on-silicon buried waveguides is reported. Thermally induced frequency upconversion enhancement is observed for the first time in Tm 3+ /Yb 3+ -codoped systems excited off-resonance at 1.064 μm. A times seven thermally induced upconversion efficiency enhancement was obtained when the waveguide's temperature was varied in the 20–120°C range. The thermal effect is believed to be associated with a temperature dependent effective absorption cross-section for the Yb 3+ -sensitizer, which depends upon the phonon occupation number in the host matrix.