An optimal system for temperature measurements by coherent anti-Stokes Raman spectroscopy (CARS) in turbulent flames and flows is presented. In addition to a single-mode pump laser and a modeless dye laser, an echelle spectrometer with a cross disperser is used. This system permits simultaneous measurement of the N2 CARS spectrum and the broadband dye laser profile. A procedure is developed to use software to transform this profile into the excitation profile by which the spectrum is referenced. Simultaneous shot-to-shot referencing is compared to sequential averaged referencing for data obtained in flat flames and in room air. At flame temperatures, the resultant 1.5% imprecision is limited by flame fluctuations, indicating that the system may have a single-shot imprecision below 1%. At room temperature, the 3.8% single-shot imprecision is of the same order as the best values reported for dual-broadband pure-rotational CARS. Using the unique shot-to-shot excitation profiles, simultaneous referencing eliminates systematic errors. At 2000 and 300 K, the 95% confidence intervals are estimated to be ±20 and ±10 K, respectively.
© 2005 Optical Society of America
(120.1740) Instrumentation, measurement, and metrology : Combustion diagnostics
(120.6780) Instrumentation, measurement, and metrology : Temperature
(190.1900) Nonlinear optics : Diagnostic applications of nonlinear optics
(300.6230) Spectroscopy : Spectroscopy, coherent anti-Stokes Raman scattering
Eric H. van Veen and Dirk Roekaerts, "Thermometry for turbulent flames by coherent anti-Stokes Raman spectroscopy with simultaneous referencing to the modeless excitation profile," Appl. Opt. 44, 6995-7004 (2005)