Giant Near-Infrared Emission Enhancement in AgAuSe Colloidal Alloy Quantum Dots via Bound States in the Continuum

The control and enhancement of spontaneous emission from quantum light sources are fundamental in quantum optics, impacting technologies such as micro-lasers, single-photon sources, and quantum sensors. Colloidal quantum dots (QDs) are promising light emitters due to their high quantum yields, narrow line widths, and tunable emission wavelengths. However, the spontaneous emission efficiency of QDs is often limited by the local density of optical states (LDOS) in conventional environments, making near-field enhancement challenging. All-dielectric metasurfaces, with their high-quality factor (Q-factor) resonant modes, offer an effective platform for fluorescence enhancement. In this work, we propose a fluorescence enhancement strategy for low-toxicity AgAuSe quantum dots in the second near-infrared (NIR-II) region. By leveraging bound states in the continuum (BICs) within dielectric metasurfaces, we achieve a significant enhancement in the near-infrared emission of AgAuSe quantum dots at room temperature. The metasurface’s quasi-BIC (Q-BIC) modes, combined with the magnetic resonance wavelength, result in a 25-fold fluorescence enhancement. This work introduces an innovative mechanism for light-field control tailored to environmentally friendly AgAuSe quantum dots in the NIR-II region, paving the way for sustainable quantum dot light sources and pollution-free quantum dot lasers.