Broadband Near-Infrared emission from Cr3+-Activated La3Ga5.54Ta0.46O14 phosphors spanning the NIR-I and NIR-II regions

Abstract

Broadband near-infrared (NIR) light sources spanning the NIR-I and NIR-II regions are of considerable interest for infrared illumination, sensing, and imaging applications. Here, we investigate a series of La₃Ga_5.54Ta_0.46O₁₄:Cr³⁺ phosphors (x = 0.01–0.10) and clarify the contributions of different Cr³⁺ emission centers to their near-infrared luminescence. Under blue LED excitation (430–460 nm), all compositions exhibit broadband NIR emission extending from approximately 600 to 1600 nm, providing continuous spectral coverage across the NIR-I and NIR-II regions. Spectral deconvolution and time-resolved photoluminescence reveal two emissive contributions: isolated Cr³⁺ ions responsible for NIR-I emission around 760 nm and exchange-coupled Cr³⁺ centers contributing to longer-wavelength emission near 1.0 μm. The relative intensities and decay dynamics of these components evolve systematically with Cr³⁺ concentration, indicating energy transfer from isolated centers to the longer-wavelength-emitting species. Temperature-dependent measurements further show that the isolated Cr³⁺ emission remains thermally stable, retaining approximately 95 % of its room-temperature intensity at 423 K, while the overall emission maintains good thermal stability. As a result of the combined contributions from these emission centers, the phosphors exhibit broadband NIR output with favorable quantum efficiency, with the optimal composition (x = 0.04) achieving an internal quantum efficiency of 76.99 %. These results demonstrate that Cr³⁺-activated La₃Ga_5.54Ta_0.46O₁₄ provides a stable oxide-based platform for broadband NIR emission spanning the NIR-I and NIR-II regions, supporting its potential use in infrared illumination and imaging technologies.