Modal demultiplexing properties of tapered and nanostructured optical fibers for in vivo optogenetic control of neural activity.
Optogenetic approaches to manipulate neural activity have revolutionized the ability of neuroscientists to uncover the functional connectivity underlying brain function. At the same time, the increasing complexity of in vivo optogenetic experiments has increased the demand for new techniques to precisely deliver light into the brain, in particular to illuminate selected portions of the neural tissue. Tapered and nanopatterned gold-coated optical fibers were recently proposed as minimally invasive multipoint light delivery devices, allowing for site-selective optogenetic stimulation in the mammalian brain [Pisanello , Neuron82, 1245 (2014)]. Here we demonstrate that the working principle behind these devices is based on the mode-selective photonic properties of the fiber taper. Using analytical and ray tracing models we model the finite conductance of the metal coating, and show that single or multiple optical windows located at specific taper sections can outcouple only specific subsets of guided modes injected into the fiber.
Istituto Italiano di Tecnologia (IIT), Center for Biomolecular Nanotechnologies, Via Barsanti SNC, 73010 Arnesano (LE), Italy ; Dipartimento di Ingegneria dell'Innovazione, Università del Salento, Via per Monteroni, 73100 Lecce, Italy ; Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA ; These authors contributed equally to this work.
Marco
M
Pisanello
Istituto Italiano di Tecnologia (IIT), Center for Biomolecular Nanotechnologies, Via Barsanti SNC, 73010 Arnesano (LE), Italy ; These authors contributed equally to this work.
Andrea
A
Della Patria
Istituto Italiano di Tecnologia (IIT), Center for Biomolecular Nanotechnologies, Via Barsanti SNC, 73010 Arnesano (LE), Italy.
Leonardo
L
Sileo
Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA.
Bernardo L
BL
Sabatini
Istituto Italiano di Tecnologia (IIT), Center for Biomolecular Nanotechnologies, Via Barsanti SNC, 73010 Arnesano (LE), Italy ; Dipartimento di Ingegneria dell'Innovazione, Università del Salento, Via per Monteroni, 73100 Lecce, Italy.
Massimo
M
De Vittorio
Istituto Italiano di Tecnologia (IIT), Center for Biomolecular Nanotechnologies, Via Barsanti SNC, 73010 Arnesano (LE), Italy.
Ferruccio
F
Pisanello
(170.0170) Medical optics and biotechnology; (220.0220) Optical design and fabrication