Detection of optical trapping of CdTe quantum dots by two-photon-induced luminescence

Abstract

Nanometer-sized CdTe quantum dots (QDs) in ${\mathrm{D}}_{2}\mathrm{O}$ can be optically trapped by a high repetition-rate picosecond Nd:YLF laser with an input power as low as $100\phantom{\rule{0.3em}{0ex}}\mathrm{mW}$. A large two-photon absorption (TPA) cross section of ${10}^{4}--{10}^{5}\phantom{\rule{0.3em}{0ex}}\mathrm{GM}$ for CdTe QDs makes it possible to detect the trapping process with TPA induced luminescence. In ${\mathrm{D}}_{2}\mathrm{O}$, the luminescence intensity of CdTe QDs was found to increase with time, whereas an intensity decrease was clearly detected in ${\mathrm{H}}_{2}\mathrm{O}$. In addition, the optically trapped CdTe QDs were fixed on a hydrophilic glass substrate. Laser trapping of QDs may provide a basic technique for quantum information and biological applications.