Multiple luminescence spanning the UV to NIR regions of Tm3+-doped silica glass microspheres pumped by 1527 nm

Fluorescence spectra of Tm³⁺-doped silica glass microspheres under excitation of a continuous wave diode laser at 1527 nm were investigated. It showed rich upconversion emissions from the high-energy states of Tm³⁺ ions, which spanned from the ultraviolet (UV) to near-infrared (NIR). Analysis indicated that the purple light emission came from a six-photon upconversion process. What's more, a broadband fluorescence emission was observed in a wavelength range of 620-935 nm. The high power density was a main advantage by confining the light in the microsphere cavities. The multiple fluorescence upconversion emissions of Tm³⁺-doped silica glasses under ∼1550 nm excitation may open a new door to explore the future visible light communication technology.