Tracking Dark Excitons with Exciton Polaritons in Semiconductor Microcavities

Area of Science:

• Solid State Physics
• Quantum Optics
• Semiconductor Nanostructures

Background:

• Dark excitons are crucial for semiconductor processes but optically challenging to study due to weak light interaction.
• Understanding dark exciton dynamics is essential for advancing semiconductor device applications.

Purpose of the Study:

• To reveal and characterize dark excitons nonresonantly injected into an InGaAs/GaAs quantum well microcavity.
• To investigate the interaction of dark excitons with the bright lower polariton mode.
• To explore the implications of dark exciton lifetime on semiconductor microcavity dynamics.

Main Methods:

• Nonresonant injection of dark excitons using a gated train of eight 100 fs pulses.
• Monitoring interactions with the bright lower polariton mode via time-resolved transmission.
• Development of a rate equation model for quantitative analysis.

Main Results:

• Observed a surprisingly long dark exciton lifetime exceeding 20 ns.
• Demonstrated a memory effect due to the dark exciton lifetime being longer than the pulse delay.
• Achieved quantitative agreement between experimental data and the proposed rate equation model.

Conclusions:

• Dark excitons possess significantly long lifetimes in semiconductor microcavities, enabling memory effects.
• The study provides a novel method for investigating optically inactive excitonic states.
• Findings offer insights into fundamental semiconductor physics and potential applications in quantum information processing.