Ultrabroad Photoemission from an Amorphous Solid by Topochemical Reduction.

Wideband near‐infrared (NIR)‐emitting materials are of current interest due to their practical utilization in light sources and tunable fiber lasers for optical sensing, imaging, and amplification. Though massive research is devoted to exploring materials activated by rare‐earth ions, transition metals, and semiconductor nanocrystals, the pursuit of photonic materials with ultra‐wideband emission over an extremely wide wavelength range is still not satisfied, especially for transparent amorphous solids which are suitable for active‐fiber applications. Here, such NIR emission is realized via topochemical reduction of bismuth in an amorphous solid. Constructing a local reduction environment around Bi extends its NIR emission to abnormal 0.8–1.9 µm with an incomparable bandwidth of >650 nm, which fully covers the whole NIR region under a single wavelength excitation, that is, from the transparency windows of biological tissue over the technically essential low‐loss optical communication. Furthermore, it is experimentally shown that the same scenario can be reproduced in other typical glass systems. It is anticipated that this strategy should help fundamentally improve the optical performance of Bi‐doped glasses and contribute to exploring new photonic materials. A facile way for strongly improving the optical performance of Bi‐doped glasses through topochemical reduction is presented. In this way, an emission bandwidth which covers the whole near‐infrared region can be realized without secondary dopants, at low dopant concentration. This provides significant advantages in the design of Bi‐based fiber optical amplifiers and lasers and beats previous materials in terms of bandwidth. [ABSTRACT FROM AUTHOR]