Size dependence of two-photon absorption in semiconductor quantum dots

Georgi L. Dakovski, Jie Shan

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Quantum confinement plays an important role in the optical properties of semiconductor quantum dots (QDs). In this work, we combine experiment and modeling to systematically investigate the size dependence of the degenerate two-photon absorption (TPA) of below-band-gap radiation in CdSe QDs. The TPA coefficient β at 800 nm of CdSe QDs of varying radii was measured using femtosecond white-light transient absorption spectroscopy by probing the pump-induced bleaching at the first exciton transition energy. β was also calculated using a model based on the multiband effective-mass approximation. Satisfactory agreement between experiment and theory was obtained. Our findings show the evolution of the TPA in the QDs from that of atom-like to bulk-like with increasing the radius R. The TPA coefficient (or the volume normalized TPA cross-section) increases with radius approximately linearly in the strong confinement regime due to the rapid increase of the joint density of states for the two-photon allowed transitions, and saturates for R > 5 nm (the exciton Bohr radius), approaching that of bulk CdSe.

Original languageEnglish (US)
Article number014301
JournalJournal of Applied Physics
Volume114
Issue number1
DOIs
StatePublished - Jul 7 2013

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quantum dots
photons
radii
absorptivity
excitons
bleaching
absorption cross sections
absorption spectroscopy
pumps
optical properties
radiation
approximation
atoms
energy

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Cite this

Dakovski, Georgi L. ; Shan, Jie. / Size dependence of two-photon absorption in semiconductor quantum dots. In: Journal of Applied Physics. 2013 ; Vol. 114, No. 1.
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Size dependence of two-photon absorption in semiconductor quantum dots. / Dakovski, Georgi L.; Shan, Jie.

In: Journal of Applied Physics, Vol. 114, No. 1, 014301, 07.07.2013.

Research output: Contribution to journalArticle

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AU - Dakovski, Georgi L.

AU - Shan, Jie

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AB - Quantum confinement plays an important role in the optical properties of semiconductor quantum dots (QDs). In this work, we combine experiment and modeling to systematically investigate the size dependence of the degenerate two-photon absorption (TPA) of below-band-gap radiation in CdSe QDs. The TPA coefficient β at 800 nm of CdSe QDs of varying radii was measured using femtosecond white-light transient absorption spectroscopy by probing the pump-induced bleaching at the first exciton transition energy. β was also calculated using a model based on the multiband effective-mass approximation. Satisfactory agreement between experiment and theory was obtained. Our findings show the evolution of the TPA in the QDs from that of atom-like to bulk-like with increasing the radius R. The TPA coefficient (or the volume normalized TPA cross-section) increases with radius approximately linearly in the strong confinement regime due to the rapid increase of the joint density of states for the two-photon allowed transitions, and saturates for R > 5 nm (the exciton Bohr radius), approaching that of bulk CdSe.

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