title: Two-photon microscopy using fiber-based nanosecond excitation.
abstract: Two-photon excitation fluorescence (TPEF) microscopy is a powerful technique for sensitive tissue imaging at depths of up to 1000 micrometers. However, due to the shallow penetration, for in vivo imaging of internal organs in patients beam delivery by an endoscope is crucial. Until today, this is hindered by linear and non-linear pulse broadening of the femtosecond pulses in the optical fibers of the endoscopes. Here we present an endoscope-ready, fiber-based TPEF microscope, using nanosecond pulses at low repetition rates instead of femtosecond pulses. These nanosecond pulses lack most of the problems connected with femtosecond pulses but are equally suited for TPEF imaging. We derive and demonstrate that at given cw-power the TPEF signal only depends on the duty cycle of the laser source. Due to the higher pulse energy at the same peak power we can also demonstrate single shot two-photon fluorescence lifetime measurements.
authors.affiliation: Lehrstuhl für BioMolekulare Optik, Fakultät für Physik, Ludwig-Maximilians-Universität München, Oettingenstr. 67, 80538 Munich, Germany; Department of Electrical Engineering, University of California, Los Angeles, California 90095, USA.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Karpf
authors.affiliation: Institut für Biomedizinische Optik, Universität zu Lübeck, Peter-Monnik-Weg 4, 23562 Lübeck, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Eibl
authors.affiliation: Institut für Biomedizinische Optik, Universität zu Lübeck, Peter-Monnik-Weg 4, 23562 Lübeck, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Sauer
authors.affiliation: Institut für Biomedizinische Optik, Universität zu Lübeck, Peter-Monnik-Weg 4, 23562 Lübeck, Germany.
authors.forename: Fred
authors.initials: F
authors.lastname: Reinholz
authors.affiliation: Institut für Biomedizinische Optik, Universität zu Lübeck, Peter-Monnik-Weg 4, 23562 Lübeck, Germany.
authors.forename: Gereon
authors.initials: G
authors.lastname: Hüttmann
authors.affiliation: Lehrstuhl für BioMolekulare Optik, Fakultät für Physik, Ludwig-Maximilians-Universität München, Oettingenstr. 67, 80538 Munich, Germany; Institut für Biomedizinische Optik, Universität zu Lübeck, Peter-Monnik-Weg 4, 23562 Lübeck, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Huber
keywords: (060.2350) Fiber optics imaging; (060.4370) Nonlinear optics, fibers; (140.3510) Lasers, fiber; (180.2520) Fluorescence microscopy; (180.4315) Nonlinear microscopy