Industrial Spectroscopic-Grade – Portable Multiplex Gas Sensing System

Opportunity

In the mid-IR region, gases exhibit absorption spectral features that are typically two orders of magnitude stronger compared to the near-IR region. This makes the mid-IR quantum cascade laser a highly suitable choice of light source for gas spectroscopy applications. QCLs offer several advantages, including broadband spectral coverage ranging from 3 to 25 μm, narrow linewidth, compact size and robustness. 

In this context, we have developed a portable gas sensing system by harnessing quantum cascade laser arrays, spanning two specific wavelength regimes: 9-10 μm and 13-14 μm. To further enhance detection sensitivity, an AI algorithm has been integrated into the sensor. Moreover, the incorporation of a hollow-core fibre as a miniaturised gas cell contributes to the overall compactness of the system. By leveraging the capabilities of quantum cascade laser, this gas sensing system overcomes critical weaknesses associated with existing approaches, particularly the lack of selectivity and inability to differentiate mixtures of gases effectively.

Technology

• A key innovation lies in our custom-built QCL array, surpassing commercially available quantum cascade lasers in performance for broadband operation wavelength regimes with tunability, expanding into 9-10 μm and the ~13-14 μm regions. This expansion is advantageous for detecting volatile organic compounds that have strong absorption features in this ranges. 
• The gas sensor has been shown to achieve 940 parts per billion (ppb) for acetylene and 470 ppb for o-xylene.
• Using a hollow-core fibre, the gas cell ensures rapid analyte charging, completing in less than 1 minute. 
• Featuring a broadband laser source, the sensor enables simultaneous detection of multiple gases. Its exceptional performance in lasing peak and transverse mode makes it an ideal light source for gas spectroscopic systems.
• Integration of an AI algorithm automates concentration calculations for target gases, presenting results on the software interface for a seamless, user-friendly experience.

Applications & Advantages  

Primary application areas: scientific research, environmental monitoring and industrial process control, with additional applications in indoor air quality monitoring and oil and gas sectors. 

Potential products: Mid-IR photoacoustic gas sensor, quantum cascade laser-based dual-comb gas sensor, cavity ring-down gas sensor and liquid sensors. 

This portable technology offers both high selectivity and sensitivity, with key benefits spanning three domains: 

1. Gas Sensing: Facilitating precise and accurate gas sensing, enabling the detection and differentiation of multiple trace gases across diverse environment. 
2. Spectroscopy / Instrumentation: Leveraging the capability to design and produce long-wavelength quantum cascade lasers, our technology proves adept for advanced spectroscopy and instrumentation applications.
3. IoT for Smart Nation: Integrating this technology into the IoT framework, contributes to building smarter and more efficient societies with improved environmental monitoring and management. 

The most critical problem of existing technologies, such as electronic and chemical sensors, lies in their lack of selectivity. They are unable to distinguish between multiple trace gases without resorting to more advanced methods like GC-MS and FTIR technology. Unfortunately, these advanced methods are both bulky and expensive, restricting their usage to laboratory settings only.