# Extreme sensitivity refractive index sensor based on lithography-free metal-dielectric cavity

## TL;DR

This paper introduces a lithography-free metal-dielectric cavity sensor with extremely high sensitivity and figure of merit for detecting refractive index changes, suitable for integrated microfluidic applications.

## Contribution

It presents a novel, simple, low-cost sensing platform with record-high sensitivity and FOM, outperforming most existing methods.

## Key findings

- Sensitivity up to 1,456,700 nm/RIU for solutions
- FOM up to 1,234,500 /RIU for solutions
- Effective in both TE and TM modes

## Abstract

The use of relatively simple structures to achieve high performance refractive index sensors has always been urgently needed. In this work, we propose a lithography-free sensing platform based on metal-dielectric cavity, the sensitivity of our device can reach 1456700 nm/RIU for solution and 1596700 nm/RIU for solid material, and the FOM can be up to 1234500 /RIU for solution and 1900800 /RIU for solid material, which both are much higher than most sensing methods. This sensor has excellent sensing performance in both TE and TM light, and suitable for integrated microfluidic channels. Our scheme uses a multi-layers structure with a 10 nm gold film sandwiched between prism and analyte, and shows a great potential for low-cost sensing with high performance.