Lensless two-photon imaging through a multicore fiber with coherence-gated digital phase conjugation

Abstract

, "Lensless two-photon imaging through a multicore fiber with coherence-gated digital phase conjugation," J. Abstract. We performed near-diffraction limited two-photon fluorescence (TPF) imaging through a lensless, multicore-fiber (MCF) endoscope utilizing digital phase conjugation. The phase conjugation technique is compatible with commercially available MCFs with high core density. We demonstrate focusing of ultrashort pulses through an MCF and show that the method allows for resolution that is not limited by the MCF core spacing. We constructed TPF images of fluorescent beads and cells by digital scanning of the phase-conjugated focus on the target object and collection of the emitted fluorescence through the MCF.

Learning to see through multimode fibers

“…The transmission of images through a MMF was first presented in 1967 by Spitz and Wertz [3] who demonstrated experimentally that the distortion introduced by modal dispersion can be undone by phase conjugation. In the intervening years numerous publications have described methods for transmitting image information through MMFs or scattering media [4][5][6][7][8][9][10][11][12][13][14][15]. These methods rely on coherent (holographic) recording of the speckle pattern detected at the distal end of the fiber and they use phase conjugation or the transmission matrix method to compensate for the effects of modal dispersion and either focus the light at the distal end or project focused images.…”

Ultrathin endoscopes based on multicore fibers and adaptive optics: a status review and perspectives

“…The proof of principle two-photon lensless endoscope reported by us and others 44,58,62 opens the door to many other nonlinear image contrasts in lensless endoscopes. Any kind of nonlinear microscopy that can proceed by point scanning and relies on a single-excitation beam, e.g., three-photon fluorescence, secondharmonic generation, and third-harmonic generation microscopy, could be implemented in a lensless endoscope following the same principles.…”

“…While our approach relies on having an MCF that is optimized for transport of ultrashort pulses, a quite different approach to two-photon imaging in lensless endoscopes is represented by the recent work by Conkey et al, 62 which, in effect, describes an approach where one can use a commercial imaging fiber bundle and partially compensate for its imperfections with coherence-gated digital phase conjugation.…”

“…45, a faster version of this method was used, where a spatial Fourier transform replaces the need to scan over ϕ proximal i . Also, an even faster method is based on digital phase conjugation, 61,62 which additionally eliminates the need for sequential, pairwise illumination of cores, but requires an external reference beam.…”

Three-dimensional microfabrication through a multimode optical fiber

“…In parallel to the progress of photo-polymerization, several techniques have been developed to focus and scan light patterns [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] and optical pulses [40][41][42][43][44] through scattering media and multimode optical fibers. Different than a lens, the multimode fiber itself does not directly allow the transmission of images or focused optical pulses.…”