Pulse pump laser induced random lasing in the CdSe quantum dots beads

Strong pump laser pulses excite CdSe quantum dot beads functionalized with COOH groups, utilizing their intrinsic photons. These photons undergo scattering by the CdSe quantum dot beads, with a significant fraction of the visible photons emitted from the devices originating from this scattering process. The scattering accelerates the photons, redirecting them toward their gain molecules within nanoseconds. Further acceleration occurs via the dye molecular potential, which encodes its structure and dynamics onto the CdSe quantum dot beads. Our experiments with laser pulses reveal that laser-induced photon lasing exhibits high sensitivity to the properties of the CdSe quantum dot beads. The random lasing process selectively targets quantum dots containing dye molecules with specific gain characteristics, guiding photons along distinct trajectories. Consequently, the photons re-collide from varying directions, dictated by the scattering behavior of the quantum dot beads. This directional dependence results in preferential forward or backward scattering along the light propagation paths. Notably, the nonlinear light intensity—reaching several percent—can be reversed for photons re-colliding from the closed path of the microcavity. This intensity sensitivity in laser-induced photon lasing provides new opportunities for probing ultrafast laser dynamics.