Experiment research on ellipsoidal structure methane using the absorption characteristics of 3.31 μm mid-infrared spectroscopy

► We have successfully designed a new light collection system to enhance mid-infrared gas absorption signal. ► Signal to noise ratio can be great improved. ► The system was employed to fabricate methane sensor with the sensitivity of 50 ppm. ► The influence of temperature variations was investigated to analyze the application of this system in different environments.