Abstract
Optical transmission modulation in PbS quantum dots is investigated using a dual-wavelength pump–probe technique. High-energy excitation at 800 nm efficiently alters the transmission of a probe beam 1100– 1600 nm spectral range, with a clear enhancement observed at longer wavelengths towards the exciton peak (2100 nm) . A decay time of less than 2.5 ps is measured for pump intensities of up to 3.8 GW/cm 2 . The maximum modulation is delayed by approximately 1 ps relative to the perfect overlap of the pump and probe pulses, the time required for the electrons to reach lower energy states. Long-term exposure shows photodegradation but the process is reversible and recovers on its own after several hours.
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