Femtosecond coherent anti-stokes Raman scattering measurement of gas temperature simultaneously from H2, N2 and CO2

Femtosecond coherent anti-Stokes Raman scattering (fs-CARS) is an ideal approach for non-invasive temperature measurement under high temperature and high pressure conditions [1], which is essentially important for applications in gasification or combustion [2]. In this study, the important combustion species hydrogen (H2), nitrogen (N2) and carbon dioxide (CO2) are used for temperature determination. Using a ∼ 7 fs ultra-broadband (∼ 650 nm - 1100 nm, 200 kHz) beam from an OPCPA laser as the pump/Stokes beam, and a ∼ 1.5 ps narrowband (∼ 516 nm, 200 kHz) beam as the probe, we show that our two-beam fs-CARS setup enables a wide simultaneously detectable range for multiple molecules, covering Raman shift up to ∼ 4160 cm-1. Moreover, we present that in a H2/N2/CO2 gas mixture, the temperature can be determined without considering the non-resonant signal simultaneously from a single spectrum of H2/CO2 fs-CARS within ∼ 3 ps probe delay [3], and also from the decay rate of N2 fs-CARS signal in the same measurement. Temperature measurements have been implemented up to 1000 K and at pressures up to 20 bar. This provides high flexibility when targeting temperature determination under different environments. The modelling for fs-CARS gas temperature determination is described in detail in [4].