Multiphoton Microscopy by Multiexcitonic Ladder Climbing in Colloidal Quantum Dots

Nir Rubin, Ben Haim, Dan Oron

Research output: Contribution to journalConference articlepeer-review


Depth resolved multiphoton microscopy is performed by collecting the fluorescent emission of two-exciton states in colloidal quantum dots. The biexciton is formed via two sequential resonant absorption events. Due to the large absorption cross-section and the long lifetime of the intermediate (singly excited) state, unprecedented low excitation energy and peak powers (down to 105W/cm2) are required to generate this nonlinear response.Depending on the quantum dot parameters, the effective two-photon cross section can be as large as 1010 GM,orders of magnitude higher than for nonresonant excitation. The biexciton emission can be differentiated from that of the singly excited state by utilizing its different transient dynamics. Alternate methods for discrimination are also discussed. This system is ideal for performing three-dimensional microscopy using low excitation power. Moreover, it enables to perform multiphoton imaging even with near-infrared emitting quantum dots, which are highly compatible with imaging deep into a scattering tissue. The depth resolution of our microscope is shown to be equivalent to a standard two-photon microscope. The system also shows slow saturation due to the contribution of higher (triply and above) excited states to the emitted signal.

Original languageEnglish
Article number71831K
JournalProgress in Biomedical Optics and Imaging - Proceedings of SPIE
Publication statusPublished - Jun 1 2009
EventMultiphoton Microscopy in the Biomedical Sciences IX - San Jose, CA, United States
Duration: Jan 25 2009Jan 27 2009


  • Biexciton
  • Multiphoton microscopy
  • Optical sectioning
  • Semiconductor quantum dots

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging

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