SBIR Phase I: Cavity-Enhanced Direct Frequency Comb Spectroscopy: A Multi-Species Technology for Fingerprinting Fugitive Emissions

This Small Business Innovation Research Phase I project will be a pivotal step towards the development of the first commercial analyzer based on Cavity-Enhanced Direct Frequency Comb Spectroscopy (CE-DFCS). This new technique overcomes the traditional divide between narrow-band, highly specific, laser-based techniques and broadband, low-resolution, multi-species methods. CE-DFCS offers the advantages of both categories in a single instrument, opening a realm of possibilities. For the proposed application of fugitive emissions monitoring, CE-DFCS will help to obtain valuable data to better understand and mitigate methane emissions from both agricultural activities and natural gas leakage. The latter issue represents an enormous problem that not only accelerates climate change, but also causes millions of dollars in economic losses and represents a risk to public safety. These issues will drive an increasing market for this type of monitoring technology: the approximately $50 million current market could potentially double within five years. Beyond this application, the versatility and capability inherent in CE-DFCS will also make it widely applicable to other industries, e.g. for real-time process control and chemometrics, where it can ultimately displace complex instruments such as Fourier transform spectrometers and gas chromatographs. The intellectual merit of this project is finding a pathway to making CE-DFCS sufficiently robust for portable precision measurements in climate research and pollution mitigation. This technology represents a major change from present day spectroscopic technologies, such as Tunable Diode Laser, Cavity Ring-Down, and Fourier Transform Spectroscopy. The resulting instrument will allow researchers and industry to more precisely identify and quantify emissions from pipelines, wells, farms, landfills, forests, swamps, and other sources. While experiments from academia have demonstrated that CE-DFCS has great potential for this application, little work has focused on robustness necessary for field use. Phase I research will focus on the critical need for long-term stability in the coupling between the frequency comb and the optical enhancement cavity, which must be impervious to vibrations and environmental changes to a much higher degree than previously demonstrated. Therefore, the research objective is to properly design, integrate and optimize the electronics with a commercial optical cavity, for robust and self-optimizing comb-cavity coupling. With the proposed design and optimized control parameters and feedback mechanics, excellent long-term stability and vibration resistance is anticipated. The obtained results will serve as a basis to further develop and optimize CE-DFCS for commercial applications.