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Creation, Movement, and Amplification of Exciton Conde nsed Phase Pulses in External Potential

Olesia Dmytruk, V. I. Sugakov

Published Jan 1, 2012• 0 citations
OpenAlex

Abstract

Moveme nt of an exciton condensed phase pulse, created by a laser pulse in double quantum wells, is studied in the presence of an external potential. It is shown that the maximum of the exciton condensed phase pulse remains stable for a long time, significantly longer than in case of exciton pulse movement in gas phase. Imposing another laser pulse may amplify exciton condensed phase pulse. Thus this system can be used for information transmission.

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Moveme nt of an exciton condensed phase pulse, created by a laser pulse in double quantum wells, is studied in the presence of an external potential. It is shown that the maximum of the exciton condensed phase pulse remains stable for a long time, significantly longer than in case of exciton pulse movement in gas phase. Imposing another laser pulse may amplify exciton condensed phase pulse. Thus this system can be used for information transmission.
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We report the coherent control of excitons in quantum wells with pairs of 150-fs infrared pulses. Oscillations in the exciton density versus inter-pump-pulse separation, which correspond to the resonant transition energy, yield new insight into coherent exciton dynamics when their phase is analyzed. We demonstrate that these oscillations are caused when the second laser pulse destroys or enhances excitons that were created by the first pulse. The coherent carrier destruction generates ultrafast exciton dynamics that are not limited by the linewidth of the optical transition.
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In this paper, we report on the ultrafast coherent control of excitons in quantum wells using a phase-locked pulse sequence generated by pulse-shaping techniques. The pulse-shaping system with a double liquid-crystal spatial light modulator (SLM), and a Ti3+-sapphire laser is used to generate phase-locked pulses. The ultrafast coherent control of the exciton population and polarization is demonstrated by the observation of the reflectivity change in the pump-probe and the diffracted power in the degenerate-four-wave-mixing (DFWM) measurements. In single quantum wells, good coherent control characteristics with 87% coherent carrier destruction are demonstrated at the low excitation power of 0.15 mW (∼1.1×1010 photons/cm2). In addition, the preliminary manipulation of the exciton population is demonstrated by the phase-locked triple pulses. In the case of coupled quantum wells, the modulation of the SLM is carefully controlled and the coherent control of both the exciton population and the polarization is demonstrated in the two different coupled quantum-well samples.