Effect factors of temperature measurements by femtosecond time-resolved CARS

Femtosecond time-resolved coherent anti-Stokes Raman spectroscopy is utilized to measure the premixed methane/oxygen/nitrogen flame temperature at atmospheric-pressure. The procedure for fitting theoretical spectra to experimental spectra is explained. The experimental results show good agreements with theoretical ones and present a good repeatability. Laser parameters are very important for accurate temperature measurements. The effects of laser parameters on temperature measurements are discussed. Laser parameters in our discussion are shown as follows. Laser pulse shape is hyperbolic secant and Lorentz, respectively. The delay time between the pump and Stokes is from -40 fs to +40 fs. The central wavelength of the pump/probe pulses is from 650 nm to 700 nm. Pulse duration is from 40 fs to 120 fs. In 2000 K, variations of delay time between the pump and Stokes pulses lead to less than 5% error and while variations of the other three parameters lead to less than 1.5% error. Timing jitter is added to the pump/probe pulses and Stokes pulses. In 2000 K, the results indicate that timing jitter of 10% lead to less than 2% error for temperature measurements. In the higher temperature measurement, the impact of laser parameters’ error is greater.