Using femtosecond differential transmission spectroscopy, we observed a "nondegenerate" biexciton, consisting of an electron-hole pair in the dot ground state and an electron-hole pair in the excited state, in InGaAs self-organized quantum dots. We resonantly pumped the ground state transition in the quantum dots and observed an induced resonance in the probe differential transmission spectrum near the first excited-state transition, which we attribute to the formation of a nondegenerate biexciton state. The binding energy of 15 meV does not change with excitation power, thus reflecting a genuine feature of few-particle states. Our theoretical model calculations show good agreement with these experimental results. When a prepulse is used to generate a population inversion in the quantum dots, we also observed the effects of nondegenerate biexcitonic correlations in differential transmission.
Bibliographical noteFunding Information:
We thank Professor Bhattacharya for the supply of QD samples. This study was supported by a grant from the National R & D Program for Cancer Control, Ministry of Health & Welfare, Republic of Korea (0720170), by the Bio R & D program through the Korea Science and Engineering Foundation funded by the Ministry of Science & Technology (KOSEF 2007-8-1158), and by a Korea Research Foundation Grant provided by the Korean Government (MOEHRD, Basic Research Promotion Fund) (KRF-2007-331-C00121).
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)