Three-Photon Absorption in Seeded CdSe/CdS Nanorod Heterostructures

摘要

Size-dependent three-photon absorption (3PA) and three-photon-excited photoluminescence (PL) of CdSe/CdS nanorod heterostructures have been investigated using Z-scan and upconversion PL techniques with 150 fs laser pulses at 1300 nm. The PL from these rods shows clear cubic power dependence, and the 3PA cross section (σ3) was found to be as high as 1.5 X 10~(-75) cm s photon~(-2) for 39 nm long rods, which is 2-4 orders of magnitude larger than those previously reported for spherical semiconductor nanocrystals under ~100 fs laser pulse excitation. Importantly, by exploiting the unique property of the seeded nanorods to exhibit strong quantum confinement even at relatively large rod sizes, a superlinear dependence of the 3PA cross section on nanoparticle volume was found and validated over a wide volume range. A simple derived relation that quantitatively describes σ3 and takes into account the laserpulse duration is proposed, thereby providing a clear basis of comparison between the σ3 values of various II- VI semiconductor nanomaterials and facilitating a more judicious choice of their use in 3PA applications.