Thulium doped (silica-alumina) hybrid nanofiber and thin film multilayered structure / Nurul Iznie Razaki

High intensity of rare earth ion emission in silica (SiO2) is highly desirable for photonics applications such as laser, display, etc. Incorporation of alumina (Al2O3) in SiO2 would reduce ion clustering and phonon energy of the glass, therefore enhance the rare earth ion emission intensity. However, previous study has shown that the rare earth ions clustering is still identifiable that it would affect the ion emission. Incorporation of the rare earth ions in nanosized structure is beneficial for unique and enhanced emission intensity. Thulium (Tm3+) doped 90SiO2-10Al2O3 (mol%) nanofibers were successfully fabricated by the sol-gel/electrospinning techniques. The nanofibers retain the fibrous structure after thermal treatment at 950°C. Tm3+ doped SiO2-Al2O3 nanofiber and thin film multi-layered structure demonstrates broad spectral width with notable high emission intensity. This multilayer structure comprised of thin film sandwiched between two nanofiber layers. The emission spectrum exhibited more than five-fold enhancement at 680 nm wavelength and about 51 nm spectral bandwidth, as compared to the emission from a thin film layer. The emission peaked at shorter wavelength by about 30 nm from the spectral peak of thin film. The manifestation of the nanostructured layers, which alters the energy levels of Tm3+ due to confinement of the ions in low dimensional structure combined with the effect from thin film, resulted in the spectral broadening and increased of emission intensity. The order of depositing nanofiber and thin film layers affects the luminescence intensity and peak spectrum wavelength. Thus, tailoring the order in which these layers are to be deposited allows a particular emission characteristic to be achieved.