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Updated: Jul 16, 2025
Resonance Fluorescence of an InGaAs Quantum Dot in a Planar Cavity Using Orthogonal Excitation and Detection
Published on: October 13, 2017
Ultrafast Cascade Charge Transfer in Multibandgap Colloidal Quantum Dot Solids Enables Threshold Reduction for
Nima Taghipour1, Mariona Dalmases1, Guy Luke Whitworth1
1ICFO, Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, 08860 Spain.
Abstract:
Achieving low-threshold infrared stimulated emission in solution-processed quantum dots is critical to enable real-life applications including photonic integrated circuits (PICs), LIDAR application, and optical telecommunication. However, realization of low threshold infrared gain is fundamentally challenging due to high degeneracy of the first emissive state (e.g., 8-fold) and fast Auger recombination. In this Letter, we demonstrate ultra-low-threshold infrared stimulated emission with an onset of 110 μJ cm-2 employing cascade charge transfer (CT) in Pb-chalcogenide colloidal quantum dot (CQD) solids. In doing so, we investigate this idea in two different architectures including a mixture of multiband gap CQDs and a layer-by-layer (LBL) configuration. Using transient absorption spectroscopy, we show ultrafast cascade CT from large band gap PbS CQD to small band gap PbS/PbSSe core/shell CQDs in LBL (∼2 ps) and mixture (∼9 ps) configurations. These results indicate the feasibility of using cascade CT as an efficient method to reduce the optical gain threshold in CQD solid films.
