Record-breaking light coupling into nanostructured optical fibers under large incident angles
Coupling of light into optical fibers is important for many applications, while for commonly used step-index optical fibers it massively drops for oblique incident angles <15 degrees, limiting their operational range to a narrow angle interval. In this work, we address this issue via inclusion of dielectric concentric ring-type nanostructures located in the core region of commercially available step-index fibers. Modification of fiber facet with the optimized ring-like nanostructure leads to polarization- and azimuthally-independent enhancement of in-coupling efficiency across the entire angle interval from 15 to 85 degrees. We develop the analytical model and show the percent-level of light in-coupling efficiency even at angles as large as 70 degrees, addressing a domain that is out-of-reach for fibers with unstructured end faces. The main result of this work is the enhancement of the in-coupling efficiency at large incident angles (<30 degrees) by several orders of magnitude with respect to a bare fiber. The results obtained are promising for any application that demands to remotely collect light under large angles, such as in-vivo spectroscopy, biosensing or quantum technology.
ITMO Univ. (Russian Federation), V. N. Karazin Kharkiv National Univ. (Ukraine)
Oleh Yermakov was born in Kharkiv, Ukraine, in 1993. He received the B.Sc. degree (cum laude) in Applied Physics from V. N. Karazin Kharkiv National University, Ukraine, in 2014, the M.Sc. degree in Photonics and Optical Information Technologies and PhD in Optics from ITMO University, Saint Petersburg, Russia in 2016 and 2020, respectively. Since January 2015, he has been with the Department of Physics and Engineering, ITMO University. Since October 2019 he has been also with V. N. Karazin Kharkiv National University. He is a member of SPIE since 2014. He was awarded SPIE Travel Scholarship in 2016, Best Student Paper Award at SPIE Optics+Optoelectronics in 2017, SPIE Optics and Photonics Education Scholarship in 2019. He is advisor of the potentially emerging SPIE Student Chapter in V. N. Karazin Kharkiv National University. His research interests include: photonics, plasmonics, surface waves, metasurfaces, fiber optics, polarization, optical spin.