Fixed-distance coupling and encapsulation of heterogeneous quantum dots using phonon-assisted photo-curing
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Fixed-distance coupling and encapsulation of heterogeneous quantum dots using phonon-assisted photo-curing Naoya Tate • Yang Liu • Tadashi Kawazoe • Makoto Naruse • Takashi Yatsui • Motoichi Ohtsu
Received: 16 August 2012 / Revised: 5 September 2012 / Published online: 25 November 2012 Ó Springer-Verlag Berlin Heidelberg 2012
Abstract We propose a novel method of coupling heterogeneous quantum dots at fixed distances and capsulating the coupled quantum dots by utilizing nanometric local curing of a photo-curable polymer caused by multistep electronic transitions based on a phonon-assisted optical near-field process between quantum dots. Because the coupling and the capsulating processes are triggered only when heterogeneous quantum dots floating in a solution closely approach each other to induce optical near-field interactions between them, the distances between the coupled quantum dots are physically guaranteed to be equal to the scale of the optical near fields. To experimentally verify our idea, we fabricated coupled quantum dots, consisting of CdSe and ZnO quantum dots and a UV-curable polymer. We also measured the photoluminescence properties due to the quantum-dot coupling and showed that the individual photoluminescences from the CdSe and ZnO quantum dots exhibited a tradeoff relationship.
1 Introduction The field of nanophotonics has seen rapid progress in recent years. Nanophotonics exploits the local interactions between nanometer-scale particles via optical near fields in order to meet the requirements of future optical N. Tate (&) Y. Liu T. Kawazoe T. Yatsui M. Ohtsu The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan e-mail: [email protected] M. Naruse National Institute of Information and Communications Technology, 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795, Japan
technologies [1]. An optical near field can also be described as a dressed photon (DP), which is a quasi-particle representing the coupled state of a photon and an electron in a nanometric space [2]. By using the energy transfer between semiconductor quantum dots (QDs) via DPs, novel nanophotonic devices and systems have been realized. Useful features such as compactness and low-energy consumption have been experimentally demonstrated [3–7]. A fundamental issue in implementing practicable nanophotonic devices and systems that consist of coupled QDs is the design and assembly of an appropriate nanometric setup using QDs to induce the intended optical nearfield interactions and corresponding optical far-field responses [8]. Although there have been several reports of self-assembled QD systems based on crystal growth [9– 12], coupling of heterogeneous QDs is not straightforward due to their physical incompatibilities. Achieving more diverse types of coupling and the corresponding optical properties requires self-assembling methods for coupledQD devices consisting of heterogeneous QDs. Moreover, in recent work by the authors, self-assembling techniques for implementing nanophotonic devices and syst
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