Taking Two-Photon Excitation to Exceptional Path-Lengths in Photonic Crystal Fiber

Gareth O. S. Williams, Tijmen G. Euser, Jochen Arlt, Philip St. John Russell, Anita C. Jones

Research output: Contribution to journalArticlepeer-review


The well-known, defining feature of two-photon excitation (TPE) is the tight, three-dimensional confinement of excitation at the intense focus of a laser beam. The extremely small excitation volume, on the order of 1 μm3 (1 femtoliter), is the basis of far-reaching applications of TPE in fluorescence imaging, photodynamic therapy, nanofabrication, and three-dimensional optical memory. Paradoxically, the difficulty of detecting photochemical events in such a small volume is a barrier to the development of the two-photon-activated molecular systems that are essential to the realization of such applications. We show, using two-photon-excited fluorescence to directly visualize the excitation path, that confinement of both laser beam and sample solution within the 20 μm hollow core of a photonic crystal fiber permits TPE to be sustained over an extraordinary path-length of more than 10 cm, presenting a new experimental paradigm for ultrasensitive studies of two-photon-induced processes in solution.
Original languageEnglish
Pages (from-to)790-793
Number of pages4
JournalACS Photonics
Issue number9
Early online date25 Aug 2014
Publication statusPublished - 17 Sep 2014


  • two-photon absorption
  • two-photon cross-section
  • nonlinear optics
  • fluorescence
  • photochemistry
  • optofluidics


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