We present a method based on digital phase conjugation to selectively excite in a multimode fiber specific optical fiber modes that follow similar optical paths as they travel through the fiber. The excited modes interfere constructively at the fiber output generating an ultrashort spatially focused pulse. The excitation of a limited number of modes following similar optical paths limits modal dispersion, allowing the transmission of the ultrashort pulse. We have experimentally demonstrated the delivery of a focused spot of pulse width equal to 500 fs through a 30 cm, 200 micrometer core step index multimode fiber. The results of this study show that two-photon imaging capability can be added to ultra-thin lensless endoscopy using commercial multimode fibers.
ACCESS THE FULL ARTICLE
Edgar E. Morales-Delgado, Ioannis N Papadopoulos, Salma Farahi, Demetri Psaltis, Christophe Moser, "Delivery of ultrashort spatially focused pulses through a multimode fiber," Proc. SPIE 9584, Ultrafast Nonlinear Imaging and Spectroscopy III, 95840I (26 August 2015);