Superradiant Anti‐Stokes Fluorescence of Organic Dye J‐Aggregates

Molecular emission with shorter wavelengths than the excitation light has diverse applications in biology, chemistry, and physics. Anti‐Stokes fluorescence (aSFL), which occurs when molecules in thermally excited vibrational states undergo electronic transitions and emit fluorescence, offers the advantage of being a one‐photon process that does not require high‐intensity, focused light, unlike multiphoton up‐conversion. However, only a few organic dyes exhibit weak, spectrally broad aSFL, limiting their usage. Here, it is demonstrated that the superradiance of dye J‐aggregates enables bright and spectrally narrow (width of ≈6 nm) aSFL emission. Furthermore, it is shown that this J‐aggregate aSFL (J‐aSFL) enables real‐time, wide‐field imaging, which is not possible with other multi‐photon methods or with monomeric aSFL. It is found that J‐aSFL is a general property across various dyes, allowing structurally tunable, narrow‐band emission suitable for multiplexed imaging of bio‐samples. Beyond imaging, the results also open new opportunities for local temperature sensing and optical cooling of organic solids.