Focus the electromagnetic field to $10^{-6} \lambda$ for ultra-high enhancement of field-matter interaction

TL;DR

This paper demonstrates a method to focus microwave electromagnetic fields to an extremely small scale of 10^{-6} times the wavelength, significantly enhancing field-matter interactions for quantum and photonic applications.

Contribution

The study introduces a novel nanowire-bowtie antenna design that achieves unprecedented microwave field localization and enhancement at deep-subwavelength scales.

Findings

Microwave field localized to 10^{-6} λ using nanowire coupling.

Field intensity enhanced by 2.0×10^8 times.

Microwave-spin interaction strength increased by 1.4×10^4 times.

Abstract

Focusing electromagnetic field to enhance the interaction with matter has been promoting researches and applications of nano electronics and photonics. Usually, the evanescent-wave coupling is adopted in various nano structures and materials to confine the electromagnetic field into a subwavelength space. Here, based on the direct coupling with confined electron oscillations in a nanowire, we demonstrate an extreme localization of microwave field down to 10$^{-6}\lambda$. A hybrid nanowire-bowtie antenna is further designed to focus the free-space microwave to this deep-subwavelength space. Detected by the nitrogen vacancy center in diamond, the field intensity and microwave-spin interaction strength are enhanced by 2.0$\times$10$^{8}$ and 1.4$\times$10$^{4}$ times, respectively. Such an extreme concentration of microwave field will further promote integrated quantum information processing, sensing and microwave photonics in a nanoscale system.