title: Real-time resilient focusing through a bending multimode fiber.
abstract: Multimode optical fibers are attractive for biomedical and sensing applications because they possess a small cross section and can bend over small radii of curvature. However, mode phase-velocity dispersion and random mode coupling change with bending, temperature, and other perturbations, producing scrambling interference among propagating modes; hence preventing its use for focusing or imaging. To tackle this problem we introduce a system capable of re-focusing light through a multimode fiber in 37ms, one order of magnitude faster than demonstrated in previous reports. As a result, the focus spot can be maintained during significant bending of the fiber, opening numerous opportunities for endoscopic imaging and energy delivery applications. We measure the transmission matrix of the fiber by projecting binary-amplitude computer generated holograms using a digital micro-mirror device controlled by a field programmable gate array. The system shows two orders of magnitude enhancements of the focus spot relative to the background.
authors.affiliation: Department of Electrical, Computer, and Energy Engineering, University of Colorado, Boulder, Colorado 80309, USA. Antonio.Caravaca@Colorado.edu
authors.forename: Antonio M
authors.initials: AM
authors.lastname: Caravaca-Aguirre
authors.forename: Eyal
authors.initials: E
authors.lastname: Niv
authors.forename: Donald B
authors.initials: DB
authors.lastname: Conkey
authors.forename: Rafael
authors.initials: R
authors.lastname: Piestun
mesh_terms: D003199:Computer Systems; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D007834:Lasers; D007909:Lenses; D012031:Refractometry / Q000295:instrumentation*