Optrode arrays for infrared neural stimulation

T. V. F. Abaya; Mohit Diwekar; S. Blair; P. Tathireddy; L. Rieth; G. A. Clark; F. Solzbacher

doi:10.1117/12.2012873

8 March 2013 Optrode arrays for infrared neural stimulation

T. V. F. Abaya, Mohit Diwekar, S. Blair, P. Tathireddy, L. Rieth, G. A. Clark, F. Solzbacher

Proceedings Volume 8565, Photonic Therapeutics and Diagnostics IX; 85655W (2013) https://doi.org/10.1117/12.2012873
Event: SPIE BiOS, 2013, San Francisco, California, United States

Abstract

Penetrating waveguide arrays made of glass (SiO_O) and silicon were fabricated for infared (IR) neural stimulation to provide 3D access to the brain or peripheral nerves for selective deep-tissue stimulation with different spatiotemporal patterns. Comprehensive bench characterization was performed to determine light delivery and loss mechanisms. Fused silica/quartz arrays have optrodes of constant geometry with a pyramidal tip at the end of a straight-edge shank; length, width, and tip angle of each optrode can be varied independently from array to array. Undoped silicon arrays are similar in form to the Utah Slant Electrode Array, which has tapered microneedles of varying length in one direction. Light transmission efficiency was investigated with input from different optical fibers. With a 120-μmm wide and 1.5-mm long glass optrode having a tip taper angle of 45° with respect to the optical axis, 70% of IR light from a butt-coupled 50-μm fiber is transmitted out of the tips; shank length and tip taper does not affect the output power. However, transmission is only 39% for a 1.5- mm long Si optrode, and less for shorter more tapered optrodes. Similar beam profiles were obtained for both arrays when glass optrodes have a 45° tip taper; decreasing the glass optrode tip angle to 30° increases the full-angle divergence from 15° to 55°, which leads to a wider yet shallower illumination volume. Results reveal that the dominant source of loss in both devices is from total internal reflection within the tips. Additional losses in silicon include tapered shank radiation and reflection from its high refractive index.

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T. V. F. Abaya, Mohit Diwekar, S. Blair, P. Tathireddy, L. Rieth, G. A. Clark, and F. Solzbacher "Optrode arrays for infrared neural stimulation", Proc. SPIE 8565, Photonic Therapeutics and Diagnostics IX, 85655W (8 March 2013); https://doi.org/10.1117/12.2012873

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KEYWORDS

Glasses

Silicon

Etching

Nerve

Infrared radiation

Tissue optics

Interfaces

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