The thermal contribution to the nonlinear refractive index of air at 1.064μm was measured with a high-finesse Fabry-Perot cavity and a 500-mW cw laser beam. At room temperature and pressure, the nonlinear refractive-index coefficient of air was found to be n<sub>2</sub><sup>(th)</sup>=(-1.9±0.2)×10 <sup>-14</sup> cm<sup>2</sup>/W for a beam waist radius of 0.23 mm and was found to be independent of the relative humidity. The thermal nonlinearities of N<sub>2</sub> , O<sub>2</sub> , and CO<sub>2</sub> were also measured, and it was found that the dominant contribution to air is its O<sub>2</sub> content.
© 2000 Optical Society of America
Sean J. Bentley, Robert W. Boyd, William E. Butler, and Adrian C. Melissinos, "Measurement of the thermal contribution to the nonlinear refractive index of air at 1064nm," Opt. Lett. 25, 1192-1194 (2000)