Excitation‐Wavelength‐Tunable Lasing in Individual Quantum Dot Superparticles

Microcavities enable precise control over light-matter interactions, supporting a wide range of applications in photonics and optoelectronics. However, conventional microcavities lack the flexibility to tailor their optical properties in a dynamic fashion. Here, the optical response of CdSe/CdS quantum dot superparticles (SPs) are studied as active microresonators characterized by photo-tunable, fingerprint-like, sharp lasing emission. Steady-state and time-resolved measurements are combined at the single SP level to show that varying the pump wavelength induces a reversible spectral shift in the SP lasing modes. Theoretical simulations reveal that the wavelength-tunable penetration depth of light within the SPs is at the origin of the experimental observations, facilitating optical coupling with wavelength-specific whispering-gallery modes. Finally, the integrative potential of this technology is demonstrated by obtaining efficient optical coupling of a single SP to an optical fiber, achieving waveguided lasing emission. These findings highlight the interplay between the structural properties of SPs and their optical behavior, placing this new technology in a favored position for next-generation portable photonic devices.