All-optical fluorescence blinking control in quantum dots with ultrafast mid-infrared pulses

TL;DR

This paper demonstrates a novel all-optical method using ultrafast mid-infrared pulses to suppress blinking in quantum dots, enhancing their stability and brightness for various applications.

Contribution

It introduces the first deterministic all-optical technique to control quantum dot blinking using combined visible and MIR excitation, without altering the sample.

Findings

MIR pulses switch QD emission from charged to neutral states.

Significant reduction in quantum dot flickering observed.

Method applicable to other emitters with charging-induced intermittency.

Abstract

Photoluminescence (PL) intermittency is a ubiquitous phenomenon detrimentally reducing the temporal emission intensity stability of single colloidal quantum dots (CQDs) and the emission quantum yield of their ensembles. Despite efforts for blinking reduction via chemical engineering of the QD architecture and its environment, blinking still poses barriers to the application of QDs, particularly in single-particle tracking in biology or in single-photon sources. Here, we demonstrate the first deterministic all-optical suppression of quantum dot blinking using a compound technique of visible and mid-infrared (MIR) excitation. We show that moderate-field ultrafast MIR pulses (5.5 $\mu$m, 150 fs) can switch the emission from a charged, low quantum yield 'grey' trion state to the 'bright' exciton state in CdSe/CdS core-shell quantum dots resulting in a significant reduction of the QD intensity flicker. Quantum-tunneling simulations suggest that the MIR fields remove the excess charge from trions with reduced emission quantum yield to restore higher brightness exciton emission. Our approach can be integrated with existing single-particle tracking or super-resolution microscopy techniques without any modification to the sample and translates to other emitters presenting charging-induced PL intermittencies, such as single-photon emissive defects in diamond and two-dimensional materials.