Plasmonic Waveguide Ring Resonators with 4 nm Air Gap and λ₀²/15 000 Mode-Area Fabricated Using Photolithography

Abstract

Plasmonic air-gap disk resonators with 3.5 μm diameter and a 4 nm thick, 40 nm wide air gap for a mode area of only λ0(2)/15,000 were fabricated using photolithography only. The resonant modes were clearly identified using tapered fiber coupling method at the resonant wavelengths of 1280-1620 nm. We also demonstrate the advantage of the air-gap structure by using the resonators as label-free biosensors with a sensitivity of 1.6 THz/nm.

Control of optical nanometer gap shapes made via standard lithography using atomic layer deposition

“…For instance, V-groove gaps are used for plasmonic light confinement. 31,32 In particular, the spotlike dimension of the cross-sectional enhancement area is capable to trap one or two particles by enhanced optical trapping at the nanoantenna without stacking more particles. 33,34 On the contrary, the nanogap structures with a high-aspect ratio composing a line-like cross-sectional enhancement area within the gap have simplified FE volume in the fields of nanoelectrodes, 35 optical circuits, 36 and optical nonlinearity measurements 8,37 compared with other gap shapes.…”

Rational and Facile Construction of 3D Annular Nanostructures with Tunable Layers by Exploiting the Diffraction and Interference of Light

“…Photolithographic patterning allows the production of structures in parallel and with high throughput on a wafer‐sized scale, which has facilitated a wide range of applications in fields such as electronics, photonics, and biomedicines . Patterning nanoscale features via photolithography, however, have been challenged by the diffraction and interference as inherent nature of light .…”

Ultra sub-wavelength surface plasmon confinement using air-gap, sub-wavelength ring resonator arrays

“…Such a strong enhancement of the E-field in a small volume is highly advantageous not only for many diverse applications such as sensors 10 11 12 13 , lasers 14 15 16 17 , and color displays 18 19 20 21 but also for fundamental control of optical phenomena 22 23 . Consequently, such gap structures, also called metal-insulator-metal (MIM) structures 24 or gap plasmons 25 , have been the subject of intense research activities 26 27 28 29 30 31 32 33 34 35 .…”

“…In this way the T-shaped gap is formed along the circumference of the disk between the sidewall of the top disk and the top surface of the bottom disk. A gap as narrow as 4 nm, with a cross-sectional mode area of 7 × 10 −5 λ 0 2 could be fabricated using photolithography, and the possibility of application for a biosensor was demonstrated 35 . However, the resonators were rather large, with a diameter of 3.5 μm, leading to large overall mode volume.…”