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IEEE Photonics Conference

Coherence Time Prolongation in a Room Temperature Quantum Dot Ensemble

Igor Khanonkin, G. Eisenstein, Johann Peter Reithmaier

Published Sep 1, 2020• 0 citations
Publisher

Abstract

Significant prolongation of the coherence time by means of photon echo has been observed in a room temperature quantum dot amplifier operating at telecom wavelength. A record-long room temperature pure dephasing time of 4.7 ps was demonstrated using a detection technique suitable for practical applications.
DOI
10.1109/ipc47351.2020.9252451

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We report measurements of ultralong coherence in self-assembled quantum dots. Transient four-wave mixing experiments at 5 K show an average dephasing time of 372 ps, corresponding to a homogeneous linewidth of 3.5 microeV, which is significantly smaller than the linewidth observed in single-dot luminescence. Time-resolved luminescence measurements show a lifetime of the dot ground state of 800 ps, demonstrating the presence of pure dephasing at finite temperature. The homogeneous width is lifetime limited only at temperatures approaching 0 K.
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Storage and manipulation of quantum information requires (nearly) perfect timing---or precisely timed pulse sequences, anyhow. In quantum memory based on photon echoes, for example, the appearance time of the echo must be determined with great accuracy. This study shows how to control photon echoes in a quantum-dot optical amplifier operating at room temperature. As the amplifier is a distributed device, propagation effects are dominant in the generation of the echo pulse, and shaping the excitation pulse serves to control the echo's appearance time and strength.