Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 16: II-VI Semiconductors I
HL 16.1: Vortrag
Montag, 26. März 2012, 15:00–15:15, EW 202
Geometry effects of nonlinear optical properties in 0D-1D II-VI semiconductor nanocrystals — •Alexander W. Achtstein1, Jonas Hennig1, Anatol Prudnikau2, Marya Hardzei2, Mikhail Artemyev2, and Ulrike Woggon1 — 1Institute of Optics and Atomic Physics, Technical University of Berlin, Berlin, Germany — 2Institute for Physico-Chemical Problems, Belarussian State University, Minsk, Belarus
Semiconductor nanoparticles have unique properties due to spatial confinement and shape control also in the nonlinear optical regime. This work studies the optical nonlinearities in colloidal 0D and 1D zinc-blende- and wurtzite-type II-VI semiconductor nanocrystals. To understand nonlinear effects at a nanoscale, spatial confinement and its influence on the nonlinear optical properties are investigated. The expected strong geometry and size dependence of the two photon absorption (TPA) cross-section has been tested by a size series of colloidal CdS dots and rods starting from a near 0D system to long 1D nanorods in a z-scan setup. A pronounced change of volume normalized TPA cross sections at the transition from dots to elongated rods has been found. While the bulk TPA coefficient of CdS is only 17GM/nm3, it grows in spherical CdS nanocrystals to 140GM/nm3 and becomes 2.3×103 GM/nm3 in elongated CdS nanorods. The contributions of spatial confinement and local field effects of the dielectric environment are evaluated separately to get a deeper insight in the confinement effect on TPA. Additional Two-Photon Luminescence Excitation measurements reveal the spectral dependence of the TPA coefficients.