Abstract

Tunable excimer laser beams are increasingly used for imaging of combustion and/or flow systems. We (1) describe the need to use known polarization phenomena in interpreting diagnostics based on Rayleigh scattering (RS); (2) present relative RS cross sections for some important species at the most relevant wavelengths, 193 and 248 nm; and (3) measure the degree of linear polarization and the locking efficiency of the excimer beam, which are important diagnostic parameters that are otherwise difficult to obtain. Laser sheets, whose direction of linear polarization are adjustable, pass through gases. The Rayleigh light goes into intensified charge-coupled dervice (CCD) cameras. We report RS cross sections, normalized to those for N2, at 193 nm for H2, O2, H2O, CO2, and CH4, and at 248 nm for Ar, H2, O2, H2O, CO2, and CH4. Even when these normalized RS cross sections are used, the diagnostics can be very sensitive to the laser beam's polarization state. For example, for CO2, the normalized cross section changes by a factor of 4 with polarization. This usually unwanted sensitivity is greatest when an unmodified tunable excimer laser is used. The degree of polarization of the lasers, as well as their locking efficiency, is derived via RS from the spherical molecules Ar and CH4.

Rayleigh scattering cross sections of combustion species at 266, 355, and 532 nm for thermometry applications

Jeffrey A. Sutton and James F. Driscoll
Opt. Lett. 29(22) 2620-2622 (2004)

Application of tunable excimer lasers to combustion diagnostics: a review

Erhard W. Rothe and Peter Andresen
Appl. Opt. 36(18) 3971-4033 (1997)

Atomic vapor filter for two-dimensional Rayleigh imaging experiments with a narrow-band KrF excimer laser

P. Gölz and P. Andresen
Appl. Opt. 35(30) 6054-6061 (1996)

Study of UV Rayleigh scattering thermometry for flame temperature field measurement

Qianlong Wang, Liqiao Jiang, Weiwei Cai, and Yi Wu
J. Opt. Soc. Am. B 36(10) 2843-2849 (2019)

Photoabsorption cross-section measurement of Ar₂F excimer at 248 nm

Kohzo Hakuta, Susumu Miki, and Hiroshi Takuma
J. Opt. Soc. Am. B 5(6) 1261-1265 (1988)