Precision measurement of the refractive index of carbon dioxide with a frequency comb

We report a higher precision measurement of the refractive index of carbon dioxide using a frequency comb as the light source in a Mach-Zehnder interferometer setup. The experimental sensitivity can reach the level of 8.8 X 10(-9). Taking into account the measurement accuracy of temperature and pressure, the experimental accuracy has a value of 1.2 X 10(-8). The measurement result has a deviation from the commonly quoted result [Old et al., J. Opt. Soc. Am. 61, 89 (1971)] by 6.4 X 10(-7) at 800 nm. (c) 2007 Optical Society of America.