Sensitive hybrid femtosecond/picosecond vibrational coherent anti-Stokes Raman scattering thermometry using optimized probe time delays

We propose a method that utilizes optimized probe time delays of 10-35 ps in hybrid femtosecond/picosecond (fs/ps) vibrational coherent anti-Stokes Raman scattering thermometry and obtains maximum temperature sensitivity from 300 to 2500K. The relationship between temperature sensitivity and the optimal probe time delay can be approximated by a power function. Sensitive measurements at flame temperatures (1700-2100K) using optimal time delays are performed in further experiments where the Raman coherence of nitrogen molecules is excited by 35-fs pump and Stokes pulses and probed with a spectrally narrow pulse generated from a 4-f pulse shaper. Temperature results at optimal time delays exhibit state-of-the-art accuracy and superior uncertainty, demonstrating its capability to achieve sensitive measurements.