Luminescence and Amplified Stimulated Emission in CdSe–ZnS-Nanocrystal-Doped TiO2 and ZrO2 Waveguides
A reproducible route for the preparation of high-quality CdSe–ZnS-doped titania and zirconia waveguides is presented. The optical properties of the resultant composite materials are found to be sensitive to the semiconducting properties of the host matrix. Titania-based composites are seen to be inherently photounstable because of photoelectron injection into the bulk matrix and subsequent nanocrystal (NC) oxidation. In comparison, zirconia composites are significantly more robust with high photoluminescence (PL) retained for annealing temperatures up to 300 °C. Both titania and zirconia composite waveguides exhibit amplified stimulated emission (ASE); however only zirconia-based waveguides exhibit long-term photostability (loss of less than 30 % ASE intensity after more than 40 min continuous excitation). We conclude that the low electron affinity of zirconia and its inherent high refractive index makes it an ideal candidate for NC-based optical waveguides.