[17a-A34-1~9] 4.1 Plasmonics and Nanophotonics

10:00 〜 10:15英語発表

[17a-A34-3] Optical chirality enhancement at the nanoscale using inversely-designed 3D nanogap antennas

〇Atsushi Taguchi¹, Keiji Sasaki¹ (1.Hokkaido Univ.)

キーワード：

chiral nanogap antenna、optical chirality enhancement、topology optimization

We present a 3D nanogap antenna with a high chiral dissymmetry––the field intensity at the nanogap is high for a particular handedness of circularly polarized incident light while not for the other. The antenna structure was found using a computational inverse design technique called topology optimization. With circularly polarized incident light implemented into the algorithm, a spiral structure was created that is too complex to attain by human intuition or imagination. We calculated the near-field intensity at the nanogap of the structure, and the resultant dissymmetry factor was as high as 1.40. We also found a 50-fold enhancement of the optical chirality within the nanogap. The chirality enhancement was elucidated with a fluid model of the chirality flux within the 3D nanoantenna, which is then correlated to light’s spin angular momentum (SAM). This finding can be a novel design strategy to enhance optical chirality density at the nanoscale using nanophotonic structures.