Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering for high-speed CH4/N-2 measurements in binary gas mixtures

作者：Engel Sascha R; Miller Joseph D; Dedic Chloe E; Seeger Thomas; Leipertz Alfred; Meyer Terrence R^*

来源：Journal of Raman Spectroscopy, 2013, 44(10): 1336-1343.

DOI：10.1002/jrs.4261

• coherent anti-Stokes Raman scattering
• ultrafast spectroscopy
• concentration measurement
• gas sensing

Hybrid femtosecond/picosecond (fs/ps) vibrational coherent anti-Stokes Raman scattering was demonstrated for high-speed, in-situ measurements of CH4/N-2 mole fractions in binary gas mixtures with temporal nonresonant suppression. A single broadband, 100-fs laser source was used to simultaneously excite CH4 and N-2 vibrational Raman transitions, characterized by a spectral separation of similar to 584cm(-1), followed by frequency-domain detection with a time-delayed ps probe pulse. In this manner, the temporal evolution of the nonresonant background and vibrational wavepackets of CH4 and N-2 could be evaluated to maximize signal and minimize interferences. A typical accuracy of similar to 95% was achieved for experimental CH4 mole fractions between 0.02 and 0.70, and a precision of similar to 4% was achieved by maximizing relative excitation energy through induced chirp in the pump and Stokes pulses. It was further shown that mole-fraction measurements were not affected by variations in bi-molecular broadened linewidths over a wide range of mixture fractions.

• 出版日期2013-10