Time-resolved four-wave mixing in an InAs/InGaAs/GaAs electrically pumped quantum-dot amplifier is measured at room temperature for different applied bias currents going from optical absorption to gain of the device. The four-wave mixing signal from 140 fs pulses shows a transition from a delayed photon-echo response in the absorption regime to a prompt free polarization decay in the gain regime. This corresponds to a pronounced reduction of the dephasing time from 250 fs at zero bias to less than 50 fs at the maximum applied current. The four-wave mixing response at transparency of the device shows a composite structure with both photon echo and free-polarization decay. This is a signature of the digital occupation number in quantum dots, resulting at transparency in a signal from dots occupied with either zero or two excitons corresponding to absorption or gain of the dot ground state. (C) 2000 American Institute of Physics.
Bibliographical noteCopyright (2000) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
Borri, P., Langbein, W. W., Hvam, J. M., Heinrichsdorff, F., Mao, M-H., & Bimberg, D. (2000). Time-resolved four-wave mixing in InAs/InGaAs quantum-dot amplifiers under electrical injection. Applied Physics Letters, 76(11), 1380-1382. https://doi.org/10.1063/1.126038