# Spiral-Grating Tapered Gold Tip Used for Micro-Nanoscale Multi-Functional Sensing

## TL;DR

A new optical sensor with a spiral-shaped gold tip is developed for high-resolution sensing and imaging at micro and nanoscale levels.

## Contribution

The paper introduces a novel fiber-integrated spiral-grating tapered gold tip SPR sensor with multifunctional sensing capabilities.

## Key findings

- The sensor achieves high space–time resolution for surface plasmon resonance sensing.
- It is successfully applied to study liquid–liquid diffusion and plasmonic enhanced fluorescence.
- The sensor is also used in scanning near-field optical microscopy.

## Abstract

Optical fiber surface plasmon resonance (SPR) sensing, as a label-free, highly sensitive, rapid-response and in situ detection technology, has demonstrated significant utility in various physical, chemical and biological detection applications. This paper focuses on a fiber-integrated microscale spiral-grating tapered gold tip SPR sensor. We first introduce the working principle and sensing capability with high space–time resolution of this SPR microsensor. Then we provide a comprehensive description of its application in the study on the important fundamental scientific issue of liquid–liquid diffusion. Finally, we demonstrate the application of the spiral-grating tapered gold tip to plasmonic enhanced fluorescence and scanning near-field optical microscopy. By systematically summarizing the excellent multifunctional sensing performance of the microscale spiral-grating tapered gold tip, this paper aims to provide new optical schemes and tools for the study on complex physicochemical processes and light-matter interactions at microscale and nanoscale.