Abstract
We hetero-paired a ∼200 nm thin film consisting of colloidal 2.5 nm PbS quantum dots deposited on semi-insulating GaAs. By exciting the thin film with laser pulses (26 ps, 10 Hz) at 1064 nm, we observed the two-photon stimulated emission of the PbS quantum dots and the GaAs host. At a certain intensity of the optical stimulus, the absorption capability of the quantum dots collectively saturates, and more photons of the laser beam reach the GaAs host, causing a bistable-like up-switch in the GaAs photoluminescence intensity. The work further addresses the determination of the two-photon absorption coefficient, which was found to be 8.6 × 10−6 m/W.
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