Three-photon excitation of quantum dots with a telecom band ultrafast   fiber laser
  We demonstrate three-photon excitation in quantum dots with a mode-locked fiber laser operating in the telecommunications band. We compare spectra and intensity dependence of fluorescence from one- and three-photon excitation of commercially available 640 nm quantum dots, using a 372 nm diode laser for one-photon excitation and 116 fs pulses from a mode-locked fiber laser with a center wavelength of 1575 nm for three-photon excitation. 
M.J. Petrasiunas, J.B.O. Wood, D. Kielpinski, E.W. Streed
physics.optics cond-mat.mes-hall