Velocity measurements with structured light transmitted through a multimode optical fiber using digital optical phase conjugation

Abstract

Lensless fiber microendoscopes enable optical diagnostics and therapy with minimal invasiveness. Because of their small diameters, multimode fibers are ideal candidates, but mode scrambling hinders the transmission of structured light fields. We present the generation of a localized fringe system at variable distances from the distal fiber end by exploiting digital optical phase conjugation. The replayed fringe system was used for quantitative metrology. Velocity measurements of a microchannel flow in the immediate proximity of the fiber end without the use of any imaging lenses are shown. Lensless multimode fiber systems are of interest especially for biomedical imaging and stimulation as well as technical inspection and flow measurements.

Tracking connectivity maps in human stem cell–derived neuronal networks by holographic optogenetics

“…DMDs can reach switching rates of several kHz but suffer from poor light or diffraction efficiency ( Ronzitti et al, 2017 ; Shemesh et al, 2017 ). Stimulation with computer-generated phase holograms is more flexible even without additional devices ( Papagiakoumou, 2013 ): It enables higher stimulation energies than DMD and organic light-emitting diodes, three-dimensional scanning ( Ronzitti et al, 2017 ), versatile fiber-optic approaches ( Büttner et al, 2020 ; Tehrani et al, 2021 ), and compensation of sample-induced aberrations ( Tehrani et al, 2021 ). Holographic optogenetic stimulation with single-cell spatial resolution and sufficient temporal precision, less than a millisecond, has been applied to brain slices and intact brain tissue ( Ronzitti et al, 2017 ; Shemesh et al, 2017 ; Gill et al, 2020 ).…”

Complex Wavefront Shaping through a Multi-Core Fiber

“…However, due to the optical path difference between individual cores, a plane-wave illumination at the proximal facet results in a random speckle pattern at the distal output. DOPC [23,24] is implemented to compensate the phase distortion [16][17][18]. The phase delay of each core is measured at the distal side using off-axis holography, and the conjugated phase is then displayed on the SLM to precompensate for the phase distortion.…”

Intensity-Only Mode Decomposition on Multimode Fibers Using a Densely Connected Convolutional Network

“…By using both optical accesses of the MMF, a fast calibration of the MMF can be achieved. Digital Optical Phase Conjugation (DOPC) is a commonly used method to enable light control through an MMF [7], [8] or coherent fiber bundle [9]. However, the application of DOPC is limited to the reconstruction or superposition of guide stars and is not used to generate arbitrary output signals.…”