Mid-infrared high-sensitive cavity-free in-situ CO gas sensing based on up-conversion detection

TL;DR

This paper demonstrates a highly sensitive, cavity-free in-situ CO gas sensor using up-conversion detection to convert mid-infrared signals to visible light, enabling real-time detection at room temperature.

Contribution

It introduces a novel up-conversion detection method for mid-infrared CO sensing that achieves high sensitivity with a compact setup and real-time capabilities.

Findings

Achieved 79.6 ppb sensitivity in cavity-free in-situ detection.

Enabled single-photon level real-time CO detection after diffuse reflection.

Demonstrated the effectiveness of up-conversion detection at room temperature.

Abstract

Carbon monoxide (CO) is a significant indicator gas with considerable application value in atmospheric monitoring, industrial production and medical diagnosis. Its fundamental vibrational band locates around 4.6 $\upmu$m and has larger absorption line strength than that of overtone band, which is more suitable for the precise identification and concentration detection of CO. In this paper, the up-conversion detection is employed to convert the mid-infrared absorption signal obtained by TDLAS to the visible light band, then a silicon-based detector is utilized for detection. By which, we can achieve the highest sensitivity of 79.6 ppb under the condition of cavity-free in-situ with an absorption range length of only 0.14 m. Furthermore, the single-photon level real-time detection of CO concentration after the diffuse reflection is realized by using SPAD. This work demonstrates the merits of the up-conversion detection in terms of its functionality at room temperature and capacity for sensitivity detection. Furthermore, it presents a design and optimization methodology that has the potential to underpin the advancement of the method towards more practical applications, like industrial process monitoring, medical diagnosis and so on.