Plasmonic Nanolenses Produced by Cylindrical Vector Beam Printing for Sensing Applications

TL;DR

This paper presents a cost-effective laser-based method to fabricate plasmonic nanorings with enhanced electromagnetic fields, suitable for nanophotonic and biosensing applications, confirmed by simulations and dye molecule detection.

Contribution

It introduces a novel maskless laser fabrication technique for plasmonic nanorings with high field enhancement, advancing scalable production for sensing technologies.

Findings

Achieved electromagnetic field enhancement at nanoring centers.

Demonstrated detection of organic dye molecules via PL signal.

Validated design with FDTD simulations and experimental measurements.

Abstract

Here, we demonstrate a simple direct maskless laser-based approach for fabrication of back-reflector-coupled plasmonic nanorings arrays. The approach is based on delicate ablation of an upper metal film of a metal-insulator-metal (MIM) sandwich with donut-shaped laser pulses followed by argon ion-beam polishing. After being excited with a radially polarized beam, the as-prepared MIM configuration of the nanorings permitted to realize efficient nanofocusing of constructively interfering plasmonic waves excited in the gap area between the nanoring and back-reflector mirror. For optimized geometric parameters of such MIM structure, substantial enhancement of the electromagnetic near-fields at the center of the ring within a single focal spot with the size of 0.37$\lambda^{2}$ can be achieved, which is confirmed by Finite Difference Time Domain (FDTD) calculations, as well as by detection of enhanced PL signal from adsorbed organic dye molecules. The simple large-scale and cost-efficient fabrication procedure used, along with relatively good tolerance to excitation beam misalignment, make the proposed structures promising for realization of various nanophotonic and biosensing platforms that utilize cylindrical vector beam as a pump source.