Large nonlinear optical properties of ternary quantum dots and nanorods

Abstract

Recently there are many reports on the nonlinear optical (NLO) and electronics properties of semiconducting binary nanocrystals such as CdSe, PbS and CdS. In the spectral regime where the photon energy (ℏω) is less than the bandgap (Eg), two photon absorption and two-photon-absorption-associated processes are dominant mechanisms. When ℏω > Eg, however, saturable absorption due to band filling mechanism plays an important role. However, very few results related to optoelectronics properties on ternary nanocrystals are reported. Here, we present large NLO properties of ternary nanocrystals such as AgInS2 quantum dots (QDs) and AgInSe2 nanorods (NRs) studied by femtosecond laser pulse at 780 nm. By employing Z-scan and transient absorption techniques, the third-order susceptibility of AgInS2 QDs and AgInSe2 NRs has been measured to be as large as 10-8 esu. The origin of NLO properties in AgInS2 QDs is due to two photon absorption. While the NLO behavior of AgInSe2 NRs is mainly contributed by saturation in the nonlinear absorption and optical Kerr nonlinearity with a recovery time determined to be a few ten picoseconds.