Assessment of SnO2-nanocrystal-based luminescent glass-ceramic waveguides for integrated photonics

For integrated photonics, waveguide structures based on rare-earth-activated glasses are potential candidates for implementing compact integrated light sources and amplifiers. However, rare-earth ions (REs) possess low absorption cross-section, and this limits the light emission and amplification efficiency. As long as the REs are involved, there are other phenomena detrimental to their luminescence quantum yield including ion-ion interactions and non-radiative relaxation processes. To solve such problems, photonic glass-ceramics can be strategic solutions. Transparent glass-ceramics combine interesting properties of both amorphous and crystalline phases and offer specific characteristics of capital importance in photonics. More important, photonic glass-ceramics can tailor and enhance the spectroscopic properties of the rare-earth ions depending on their compositions and nature. In this work, we studied SnO-nanocrystal-based transparent glass-ceramic planar waveguides activated by rare-earths to give solutions for the problems mentioned above and enhance the rare-earth luminescence efficiency for integrated photonics. SiO-SnO:Er planar waveguides containing 30 mol% SnO nanocrystals were fabricated by sol-gel method and dip-coating technique. The planar waveguides were assessed by various characterization techniques to ensure the applicability of such glass-ceramics for integrated photonics. The experimental assessment of the SiO-SnO:Er planar waveguides focused on the key considered photonic characteristics including the structural, morphological, spectroscopic, and especially optical waveguiding properties. The photoluminescence measurements put in evidence the role of SnO nanocrystals as efficient Er luminescence sensitizers. Moreover, the incorporation of Er ions in SnO nanocrystals was demonstrated to reduce the effect of non-radiative relaxation processes on the luminescence of the Er ions and thus led to higher luminescence efficiency. Majority of the Er ions (97%) was confirmed to be imbedded in the SnO nanocrystals. The SiO-SnO:Er glass-ceramic planar waveguides have confined propagation modes, step-index profile with high confinement of 82% at 1542 nm and especially, low losses of 0.6 ± 0.2 dB/cm at 1542 nm.