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Proceedings Paper

Two-photon absorption spectra of CdTe quantum dots
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Paper Abstract

Both degenerate and nondegenerate two-photon absorption (2PA) spectra are studied in two different samples of CdTe quantum-dots in borosilicate glass hosts. One sample (CdTe-600) contains quantum-dots of radius 3.2 ± 0.2 nm and has its absorption edge at 600nm. The other sample (CdTe-750) contains quantum-dots of radius 6.6 ± 0.9 nm and absorption edge at 750nm. CdTe-600 contains quantum-dots with a narrower size distribution than CdTe-750. Consequently, the peaks corresponding to discrete transitions are more clearly visible in CdTe-600 than in CdTe-750. Both nondegenerate and degenerate spectra for these samples show a marked difference from bulk CdTe. In CdTe-750 the two-photon absorption spectrum has a shape similar to that for bulk solids but for CdTe-600 the 2PA spectrum is somewhat different from that expected for the bulk. In the Z-scan measurements we also observed a photo-darkening effect, which is accompanied by an increase in the measured effective 2PA coefficient. All results suggest that 2PA cannot be predicted by the bulk theory especially near to the 2PA edge, that the 2PA in quantum dots is generally smaller than would be expected for the same volume of bulk semiconductor with the same band edge, and that the quantum-dot size and size distribution play important roles in the 2PA spectral behavior and magnitude.

Paper Details

Date Published: 18 August 2005
PDF: 10 pages
Proc. SPIE 5931, Nanoengineering: Fabrication, Properties, Optics, and Devices II, 59310U (18 August 2005); doi: 10.1117/12.617338
Show Author Affiliations
Lazaro A. Padilha, College of Optics and Photonics/Univ. of Central Florida (United States)
Univ. Estadual de Campinas (Brazil)
Jie Fu, College of Optics and Photonics/Univ. of Central Florida (United States)
David J. Hagan, College of Optics and Photonics/Univ. of Central Florida (United States)
Eric W. Van Stryland, College of Optics and Photonics/Univ. of Central Florida (United States)
Carlos L. Cesar, Univ. Estadual de Campinas (Brazil)
Luiz C. Barbosa, Univ. Estadual de Campinas (Brazil)
Carlos H. B. Cruz, Univ. Estadual de Campinas (Brazil)


Published in SPIE Proceedings Vol. 5931:
Nanoengineering: Fabrication, Properties, Optics, and Devices II
Elizabeth A. Dobisz; Louay A. Eldada, Editor(s)

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