Abstract
Superbroad infrared (IR) band emissions expanding from 1100–1700 nm were observed in Er2O3, Pr2O3, Nd2O3, and Sm2O3 polycrystals under 980 nm excitation, which cover all the IR telecommunication windows and are the broadest bands obtained until now. The broadening of the bands mainly originates from the unusual two-photon and three-photon upconversion (UC) IR transitions. The strong power dependence of the IR emissions (n>5) suggests the photon avalanche UC mechanism. The discovery in this work is significant for future broadband communication devices.