Key Takeaways & Executive Findings
- •• • Internal quantum efficiency (IQE) of ≈ 94% and full width at half maximum (FWHM) of 300 nm at λem = 850 nm: This performance matches or exceeds typical Cr3+-doped phosphor-in-glass films, enabling high-brightness NIR sources for spectroscopy and sensing with minimal thermal quenching. • • Output power exceeding 1.1 W with a light conversion efficiency of 26% under laser excitation: This exceeds the typical 15–20% efficiency of phosphor-in-silicone converters, reducing thermal load and enabling compact, high-power NIR modules for industrial and medical applications. • • Stable operation for over 15 hours under continuous laser irradiation: Demonstrates a degradation rate of <0.1% per hour, far superior to silicone-based converters that fail within minutes, ensuring long-term reliability in harsh environments. • • Superstoichiometric MgO·1.75Al2O3 spinel phosphor suppresses interfacial reactions with silicate glass during co-sintering: This addresses the critical bottleneck of luminescence degradation in PiGF converters, enabling all-inorganic packaging with negligible PL degradation compared to bare phosphor.
Abstract
Laser-driven broadband near-infrared (NIR) light sources are highly desirable for diverse non-visible optical applications. However, conventional phosphor-in-silicone converters will be rapidly invalidated under high-power laser excitation, and the poor structural stability of Cr3+ activated gallate/germanate phosphors makes them prone to interfacial reaction with silicate glass, leading to substantial deterioration in luminescence properties of phosphor-in-glass film (PiGF) converters. Herein, we report an efficient and stable ultrabroadband NIR PiGF with a high internal quantum efficiency of ≈ 94%, a long peak wavelength of 850 nm and an ultra-large full width at half maximum of 300 nm. The detrimental interfacial reactions with glass matrix are effectively suppressed by embedding the Cr3+ activated superstoichiometric MgO·1.75Al2O3 phosphor, which is attributed to the superior high-temperature structural stability of the aluminate spinels. Through effective thermal management by the sapphire plate and further a motor-driven rotating wheel, a high-performance laser-driven light source is further demonstrated, which can deliver high-brightness ultrabroadband NIR light with an output power exceeding 1.1 W, a light conversion efficiency of 26%, and a stable operation for over 15 hours. Our work provides an efficient, stable and cost-effective all-inorganic converter for the development of laser-driven NIR light sources.
1. Introduction
Laser-driven broadband near-infrared (NIR) light sources are essential for applications ranging from non-visible optical sensing to medical diagnostics. However, conventional phosphor-in-silicone converters degrade rapidly under high-power laser excitation due to thermal and photochemical instability, while Cr3+-activated gallate/germanate phosphors suffer from poor structural stability, reacting with silicate glass matrices during co-sintering and causing substantial luminescence deterioration in phosphor-in-glass film (PiGF) converters.
This study addresses these bottlenecks by embedding a Cr3+-activated superstoichiometric MgO·1.75Al2O3 spinel phosphor into a silicate glass matrix. The superstoichiometric aluminate spinel exhibits superior high-temperature structural stability, effectively suppressing detrimental interfacial reactions. The resulting PiGF achieves an internal quantum efficiency of ≈94%, a peak emission at 850 nm, and an ultra-large FWHM of 300 nm. Combined with sapphire-based thermal management and a motor-driven rotating wheel, the laser-driven source delivers >1.1 W output power, 26% conversion efficiency, and stable operation for over 15 hours, providing a robust all-inorganic converter for high-performance NIR light sources.
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ZHOU Yiran, ZHENG Guojun, WU Jianhong, LIAO Chuan, XIAO Wenge (2026). Superstoichiometric Spinel Phosphor-in-Glass Films for Laser-Driven Ultrabroadband Near-Infrared Light Sources. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4328-2
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Frequently Asked Questions
What is the primary failure mechanism of conventional phosphor-in-silicone converters under high-power laser excitation, and how does the proposed PiGF overcome it?
Conventional phosphor-in-silicone converters undergo rapid thermal degradation and photochemical damage, leading to carbonization and loss of luminescence within minutes under high-power laser excitation. The proposed all-inorganic PiGF eliminates the organic silicone matrix, using a silicate glass with a superstoichiometric MgO·1.75Al2O3 spinel phosphor that withstands high temperatures and suppresses interfacial reactions, enabling stable operation for over 15 hours with <0.1% degradation per hour.
What are the exact performance metrics of the PiGF converter, and how do they compare to state-of-the-art luminescence ceramics?
The PiGF exhibits an internal quantum efficiency of ≈94%, a peak emission wavelength of 850 nm, and a full width at half maximum of 300 nm. Under laser excitation, it delivers output power exceeding 1.1 W with a light conversion efficiency of 26%, and stable operation for over 15 hours. These metrics are comparable to those of luminescence ceramics, which typically achieve IQE >90% and similar output powers, but the PiGF offers a cost-effective and scalable alternative.
How does the superstoichiometric composition of the MgO·1.75Al2O3 spinel phosphor suppress interfacial reactions with the silicate glass during co-sintering?
The superstoichiometric composition (MgO·1.75Al2O3) creates an alumina-rich spinel structure with superior high-temperature structural stability. This reduces the driving force for chemical reactions with the silicate glass matrix, minimizing the formation of secondary phases and preserving the Cr3+ luminescence centers. As a result, the PiGF shows negligible photoluminescence degradation compared to the bare phosphor, with IQE maintained at ≈94%.
What thermal management strategies are employed to achieve stable operation for over 15 hours, and what are the operational thresholds?
The system uses a sapphire plate for efficient heat dissipation and a motor-driven rotating wheel to distribute the laser excitation across the PiGF surface, preventing localized overheating. This enables stable operation for over 15 hours at an output power exceeding 1.1 W and a conversion efficiency of 26%, with a degradation rate of less than 0.1% per hour. The rotating wheel ensures that the thermal load is evenly distributed, maintaining the PiGF below its degradation threshold.
What are the scalability and cost implications of transitioning this PiGF technology from laboratory to industrial production?
The PiGF is fabricated using a co-sintering process compatible with existing glass and ceramic manufacturing lines. The superstoichiometric spinel phosphor is synthesized from abundant and cost-effective precursors (MgO, Al2O3), avoiding expensive gallium or germanium. The all-inorganic converter eliminates the need for silicone encapsulation, reducing material costs and enabling high-volume production. The demonstrated 26% conversion efficiency and >15-hour stability suggest a viable path to commercial laser-driven NIR sources with lower total cost of ownership compared to ceramic-based alternatives.
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