Magnetic Nature of Light Transmission through a 5-nm Gap

• Published in: Scientific reports Vol. 8; no. 1; pp. 2751 - 6
• Main Authors: Yang, Hyosim, Kim, Dai-Sik, Kim, Richard H. Joon-Yeon, Ahn, Jae Sung, Kang, Taehee, Jeong, Jeeyoon, Lee, Dukhyung
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 09.02.2018; Nature Publishing Group; Nature Portfolio
• Subjects: 142/126; 639/624/400/1021; 639/624/400/1103; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Disease transmission; Humanities and Social Sciences; Light transmission; Magnetic fields; Magnetism; multidisciplinary; Science; Science & Technology - Other Topics; Science (multidisciplinary)
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-018-21037-1

Slot antennas have been exploited as important building blocks of optical magnetism because their radiations are invoked by the magnetic fields along the axes, as vectorial Babinet principle predicts. However, optical magnetism of a few-nanometer-width slit, for which fascinating applications are found due to the colossal field enhancement but Babinet principle fails due to the nonnegligible thickness, has not been investigated. In this paper, we demonstrated that the magnetic field plays a dominant role in light transmission through a 5-nm slit on a 150-nm-thick gold film. The 5-nm slit was fabricated by atomic layer lithography, and the transmission was investigated for various incident angles by experiment and simulation at 785-nm wavelength. We found that, due to the deep subwavelength gap width, the transmission has the same incident angle dependence as the tangential magnetic field on the metal surface and this magnetic nature of a nanogap holds up to ~100-nm width. Our analysis establishes conditions for nanogap optical magnetism and suggests new possibilities in realizing magnetic-field-driven optical nonlinearities.