Sub-100 nm Focusing of Short Wavelength Plasmons in Homogeneous 2D Space

• Published in: Nano letters 2014-10, Vol.14 (10), p.5598-5602
• Main Authors: Gjonaj, B, David, A, Blau, Y, Spektor, G, Orenstein, M, Dolev, S, Bartal, G
• Format: Article
• Language: English
• Subjects: Applied sciences; Collective excitations (including excitons, polarons, plasmons and other charge-density excitations); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronics; Exact sciences and technology; Invariants; Molecular electronics, nanoelectronics; Nanostructure; Optical microscopes; Physics; Plasmons; Platforms; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Silver; Surface and interface electron states; Two dimensional; Wavelengths
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl502080n

We present a direct measurement of short-wavelength plasmons focused into a sub-100 nm spot in homogeneous (translation invariant) 2D space. The short-wavelength (SW) surface plasmon polaritons (SPP) are achieved in metal–insulator–insulator (MII) platform consisting of silver, silicon nitride, and air. This platform is homogeneous in two spatial directions and supports SPP at wavelength more than two times shorter than that in free space yet interacts with the outer world through the evanescent tail in air. We use an apertureless (scattering) near-field scanning optical microscope (NSOM) to map directly the amplitude and phase of these SW-SPP and show they can be focused to under 70 nm without structurally assisted confinement such as nanoantennas or nanofocusing. This, along with the use of visible light at 532 nm which is suitable for optical microscopy, can open new directions in direct biological and medical imaging at the sub-100 nm resolution regime.