Filamentation-based, two-beam, 1-kHz, and single-shot N2 vibrational CARS thermometry in high-temperature flames

Abstract

We achieve two-beam, 1-kHz, and single-shot N2 vibrational coherent anti-Stokes Raman scattering (CARS) thermometry using hybrid femtosecond/picosecond CARS in high-temperature flames. Ultrabroadband pump/Stokes pulses are generated employing the filamentation of high-power femtosecond pulses and can excite the Raman shift up to ∼3000 cm−1. This configuration can avoid the need of a long hollow-core fiber and an additional supercontinuum compressor to obtain ultrabroadband pulses. The quasi-common-path second harmonic bandwidth compression system is utilized to generate narrow-band and sideband-free picosecond pulses, which are employed as the probe pulses in the CARS process. The accuracy and the precision of the fitting results from 1000 consecutive single-shot spectra at a target temperature of 1706 K are 0.66% and 4.47%, respectively. The results demonstrate that the simplified two-beam system has the potential for dynamic and accurate temperature measurement in practical applications.