Gas detection sensitivity of hybrid fs/ps and fs/ns CARS

Coherent anti-Stokes Raman scattering (CARS) is commonly used for thermometry and concentration measurement of major species. The quadratic scaling of CARS signal with number density has limited the use of CARS for detection of minor species, where more sensitive approaches may be more attractive. However, significant advancements in ultrafast CARS approaches have been made over the past two decades, including the development of hybrid CARS demonstrated to yield greatly increased excitation efficiencies. Yet, detailed detection limits of hybrid CARS have not been well established. In this Letter, detection limits for N-2, H-2, CO, and C2H4 by point-wise hybrid femtosecond (fs)/picosecond (ps) CARS are determined to be of the order of 10(15) molecules/cm(3). The possible benefit of fs/nanosecond (ns) hybrid CARS is also discussed. (C) 2022 Optica Publishing Group

Automated summary

Coherent anti-Stokes Raman scattering (CARS) is commonly used for thermometry and concentration measurement of major species. However, its use for detecting minor species is limited due to the quadratic scaling of CARS signal with number density. Recent advancements in ultrafast CARS approaches, including hybrid CARS, have increased the excitation efficiencies. This study determines the detection limits of N-2, H-2, CO, and C2H4 using point-wise hybrid femtosecond (fs)/picosecond (ps) CARS to be on the order of 10(15) molecules/cm(3), and discusses the possible benefits of fs/nanosecond (ns) hybrid CARS.