Excitation‐Wavelength‐Tunable Lasing in Individual Quantum Dot Superparticles

Abstract 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.