Oriented Blue-Violet-Suppressed Warm-White Light Emission from Sintered Gold Titanium Dioxide Structures Based on Near-Field Confinement

Abstract

Directional light sources are highly desirable for next-generation photonic and display technologies, yet achieving broadband directional light emission without external optical elements remains a major challenge. In addition, conventional broadband emitters typically contain excessive high-energy blue-violet spectral components, limiting their suitability for visually comfortable lighting applications. Here, we report a broadband warm-white emitter that generates directional light output without external optical components while intrinsically suppressing blue-violet emission under NIR excitation. The emitter consists solely of Au nanoparticles (Au NPs) as the light-emitting centers and TiO2 as the protective layer, while spontaneously forming a microlens-shaped surface during synthesis. Under plasmon-enhanced NIR excitation, the Au NP interface system undergoes nonlinear excitation, energy thermalization, and defect-state coupling, ultimately giving rise to broadband radiative emission. The directional emission further reshapes from near-field effects induced by the sintered microlens structure. This work provides a materials-level strategy for integrating directional emission, spectral safety, and structural simplicity into a single white-light platform, offering opportunities for multifunctional photonic materials and devices.