Precision of single‐shot dual‐broadband rotational CARS thermometry with single‐mode and multi‐mode Nd:YAG lasers

Abstract

The precision of single-shot coherent anti-Stokes Raman spectroscopy (CARS) thermometry is an important characteristic for the application of CARS in various combustion devices such as internal combustion engines. It is generally assumed that the precision of CARS is directly related to the spectral noise of the interacting laser fields, and previous studies have presented a theoretical model describing the behaviour of the noise as a function of various experimental parameters. In this work, the aim was to test the results predicted by the previously developed model for dual-broadband rotational CARS. We studied the precision of evaluated temperatures in pure nitrogen under different experimental conditions, namely the dependence of precision on the gas pressure and on the linewidth of the narrowband laser (the Nd : YAG laser). It was demonstrated that our experiments reproduce the main features of the model, and that a single-mode Nd : YAG laser leads to better precision than a multi-mode Nd : YAG laser for dual-broadband rotational CARS thermometry.

Thermometry for turbulent flames by coherent anti-Stokes Raman spectroscopy with simultaneous referencing to the modeless excitation profile

“…Single-shot imprecision ranges from 4% to 5% at room temperature to 6% to 7% near 2000 K for measurements above a water-cooled porous-plug burner in the burnt gases of a premixed methane-air flame, 27 in hot air in a high-temperature oven, 24,28 -30 in convective heat transfer flows, 31 and at high pressures. 32,33 In an internal-combustion engine a 1% relative standard deviation was obtained, 34 but it is still not understood why these measurements ended up with lower relative standard deviations than detected in similar laboratory conditions. 35 Recently a dual-pump, dual-broadband CARS system was demonstrated to simultaneously probe purerotational as well as rovibrational transitions.…”

“…9,10,12,24 It compares well with the best values reported for pure-rotational CARS systems. 24,[27][28][29]31,33,35 An interesting option to improve on this precision would be the application of an optical pulse stretcher. 47 In summary, the rovibrational CARS system presented here combines optimal single-shot precision at room and at flame temperatures.…”

Rotational CARS thermometry at high temperature (1800 K) and high pressure (0.1–1.55 MPa)

“…Results from two cases are shown: evaluation of a major part of the spectrum (above ¾110 cm 1 ) represented by filled squares and evaluation of a limited spectral region (above ¾178 cm 1 ) represented by filled triangles. 9 In the same investigation a detailed theoretical explanation has been given for this behaviour. 22.…”

Coherent anti-Stokes Raman scattering microscopy with spectrally tailored ultrafast pulses

“…Elaborate pulsed laser systems with one narrow and one or more broad band outputs have been developed and are favored by many research groups. 19,20 Recently several new CARS microscopy techniques have been developed. Based on the pioneering CARS microscopy work by Duncan et al using two dye lasers, 13 Xie et al have developed a more advanced system in which two Ti: Sapphire oscillators were employed.…”