Near‐Unity and Near‐Zero‐Thermal‐Quenching Luminescent GAGG–Al₂O₃:Cr³⁺ Ceramic via Containerless Solidification and Glass Crystallization Methods for NIR Spectroscopy Application

Abstract Near‐infrared (NIR) light is widely used in real‐time testing fields such as organic component detection and biological imaging owing to its strong tissue penetration and nondestructive properties. However, the performance of NIR phosphor‐converted light‐emitting diodes (pc‐LEDs) is constrained by limitations in efficiency and output power. In this work, the Gd 3 Al 3 Ga 2 O 12 (GAGG)–Al 2 O 3 :Cr 3+ ceramics are successfully synthesized via containerless solidification and glass crystallization methods. The Al 2 O 3 matrix functions as an optically active component akin to GAGG, mitigating concentration quenching effects while preserving strong light absorption. Under 450 nm light excitation, the ceramic exhibits intense NIR luminescence, achieving exceptional internal/external quantum efficiencies (IQE/EQE = 96.8%/46.1%) and remarkable thermal stability (94.3%@150 °C). The ceramic‐converted NIR LED (cc‐LED) demonstrates outstanding photoelectric conversion efficiency (28%@350 mA) and robust NIR light output (236 mW@350 mA). Additionally, the laser diode (LD)‐excited NIR device achieves an exceptional watt‐level light output (1.52 W@10 W mm −2 ). As a proof of concept, this NIR light source shows immense potential for diverse applications including plant illumination, nondestructive testing, and bioimaging systems. Therefore, this innovative GAGG–Al 2 O 3 :Cr 3+ NIR‐LED&LD not only broadens the practical application scope of NIR light sources but also offers a transformative pathway for next‐generation compact high‐power devices in this field.