Quantification and Modulation of Photon Recycling in High‐Efficiency Fluorescent Antennas for Enhanced Communication Performance

Fluorescent antennas (FAs) have emerged as superior optical concentrators for optical wireless communication (OWC). By combining high optical gain with a large field of view, FAs offer a promising alternative to traditional lenses. However, the significant spectral overlap between absorption and photoluminescence within these antennas triggers complex internal photon recycling (PR) mechanisms that remain insufficiently understood. This phenomenon substantially complicates the optimization of their communication performance. In this work, we fabricated high‐quality CsPbBr 3 QD‐based FAs via 3D printing and successfully characterized the internal PR process. We established a quantitative correlation linking the fluorescence lifetime, measured by edge time‐resolved photoluminescence spectroscopy, to the number of PR events. The validity and precision of this correlation were confirmed through independent transient absorption (TA) spectroscopy measurements and photon random‐walk simulations. Leveraging these insights, we introduce a novel method to strategically modulate the PR process using an optical filter, achieving a substantial 77% enhancement in bandwidth and a superior on–off keying (OOK) data rate. This work clarifies the PR process and its influence on FA performance, presenting a readily implementable strategy for developing high‐efficiency OWC systems through precise PR regulation.