Title

Optimization of Band Structure and Quantum-Size-Effect Tuning for Two-Photon Absorption Enhancement in Quantum Dots

Authors

Authors

L. A. Padilha; G. Nootz; P. D. Olszak; S. Webster; D. J. Hagan; E. W. Van Stryland; L. Levina; V. Sukhovatkin; L. Brzozowski;E. H. Sargent

Comments

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Abbreviated Journal Title

Nano Lett.

Keywords

Nonlinear optics; two-photon absorption; quantum dots; nonlinear; spectroscopy; lead salt; band structure; OPTICAL NONLINEARITIES; SEMICONDUCTOR MICROCRYSTALLITES; MEDIATED; ENHANCEMENT; EXCITATION; PBS; NANOCRYSTALS; SPECTROSCOPY; DYES; Chemistry, Multidisciplinary; Chemistry, Physical; Nanoscience &; Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied; Physics, Condensed Matter

Abstract

The two-photon absorption, 2PA, cross sections of PbS quantum dots, QDs, are theoretically and experimentally investigated and are shown to be enhanced with increasing quantum confinement. This is in contrast to our previous results for CdSe and CdTe QDs where the reduced density of states dominated and resulted in a decrease in 2PA with a decrease in QD size. Qualitatively this trend can be understood by the highly symmetric distribution of conduction and valence band states in PbS that results in an accumulation of allowed 2PA transitions in certain spectral regions. We also measure the frequency nondegenerate 2PA cross sections that are up to five times larger than for the degenerate case. We use a k.p four-band envelope function formalism to model the increasing trend of the two-photon cross sections due to quantum confinement and also due to resonance enhancement in the nondegenerate case.

Journal Title

Nano Letters

Volume

11

Issue/Number

3

Publication Date

1-1-2011

Document Type

Article

Language

English

First Page

1227

Last Page

1231

WOS Identifier

WOS:000288061500054

ISSN

1530-6984

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