title: Efficient optical trapping of CdTe quantum dots by femtosecond laser pulses.
abstract: The development in optical trapping and manipulation has been showing rapid progress, most of it is in the small particle sizes in nanometer scales, substituting the conventional continuous-wave lasers with high-repetition-rate ultrashort laser pulse train and nonlinear optical effects. Here, we evaluate two-photon absorption in optical trapping of 2.7 nm-sized CdTe quantum dots (QDs) with high-repetition-rate femtosecond pulse train by probing laser intensity dependence of both Rayleigh scattering image and the two-photon-induced luminescence spectrum of the optically trapped QDs. The Rayleigh scattering imaging indicates that the two-photon absorption (TPA) process enhances trapping ability of the QDs. Similarly, a nonlinear increase of the two-photon-induced luminescence with the incident laser intensity fairly indicates the existence of the TPA process.
authors.affiliation: Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University , 1001 Ta Hsueh Rd., Hsinchu 30010, Taiwan.
authors.forename: Wei-Yi
authors.initials: WY
authors.lastname: Chiang
authors.forename: Tomoki
authors.initials: T
authors.lastname: Okuhata
authors.forename: Anwar
authors.initials: A
authors.lastname: Usman
authors.forename: Naoto
authors.initials: N
authors.lastname: Tamai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Masuhara