Visible‐Light‐Driven Nd ³⁺ Emission Enabled by a Garnet‐Based Cr ³⁺ ‐Doped Phosphor–Glass Composite for Broadband‐to‐NIR Spectral Conversion

ABSTRACT Conventional pulsed Nd‐doped solid‐state lasers (SSLs) typically employ broadband white‐light lamps as the primary pump source, enabling the generation of high‐energy laser outputs up to hundreds of joules. However, the limited spectral overlap between the visible‐light emission and the absorption bands of Nd 3+ ions hinders further system simplification and cost reduction. In this work, we present a spectrally matched phosphor, La 3 Sc 2 Ga 3 O 12 :Cr 3+ (LSGG:Cr 3+ ), which exhibits exceptional spectral alignment with the YAG:Nd 3+ absorption band, facilitating efficient blue‐to‐near‐infrared (NIR) optical down‐conversion for resonant pumping of Nd 3 ⁺ ions. Spectroscopic analyses identify an optimal Cr 3+ doping concentration of 1 at.% and a phonon coupling energy of 21 meV, contributing to the phosphor's high internal quantum yield (>78%) and ensuring efficient optical conversion. To address thermal challenges, we developed a novel ultrathin (105 µm) phosphor‐glass composite (PGC), which demonstrates superior thermal stability and maintains luminescent dynamics. When integrated with a broadband light source, the LSGG:Cr 3+ ‐based PGC converts poorly absorbed visible light into highly absorbable NIR light for Nd 3+ ions, serving as an effective nonlinear spectral converter. This study establishes a promising energy‐saving approach for broadband‐pumped SSLs through advanced luminescent spectral engineering.