# High performance graphene oxide-based humidity sensor integrated on a photonic crystal cavity

## TL;DR

This paper presents a highly sensitive, fast-response humidity sensor using graphene oxide on a photonic crystal cavity, enabling precise and rapid humidity detection suitable for applications like human breathing monitoring.

## Contribution

The work introduces a novel high-performance humidity sensor integrating graphene oxide with a photonic crystal cavity, achieving ultrahigh sensitivity and sub-100 ms response time.

## Key findings

- Resonant wavelength shifts of 0.68 nm/%RH in 60%-85% RH range
- Sensitivity exceeding 3.9 dB/%RH
- Response time less than 100 ms

## Abstract

We report a high performance relative humidity (RH) microsensor by coating a few-layer graphene oxide (GO) flake over a photonic crystal (PC) cavity. Since the GO layer has a high water-activity and interacts with the evanescent cavity mode strongly, the exposure of GO-PC cavity in varied humidity levels results in significant resonant wavelength shifts, showing a slope of 0.68 nm/%RH in the range of 60%-85% RH. By interrogating the power variation of the cavity reflection, the microsensor presents an ultrahigh sensitivity exceeding 3.9 dB/%RH. Relying on the unimpeded permeation of water molecules through the GO interlayers and microscale distribution of the cavity mode, the integrated sensor has a response time less than 100 ms, which promises successful measurements of human breathing. Combining with the ease of fabrication, this high performance RH sensor has potential applications requiring optical access, device compactness, and fast dynamic response.