Abstract

Experiments were performed using the Lawrence Livermore National Laboratory Nova laser to measure the nonlinear refractive index of air and argon gases via the technique of intensity-dependent ellipse rotation. These measurements directly impact our understanding of beam propagation issues and solid-state frequency conversion performance for large laser systems. Our experimental values for the nonlinear refractive index at 293 K, 1 atm, are ~0.98 × 10⁻¹⁶ esu for air and 0.23 × 10⁻¹⁶ esu for argon. We surveyed the recent literature to compile what we consider the most reliable values for the nonlinear indices of air (nitrogen and oxygen) and argon. This has been accomplished by deducing the third-order susceptibility tensor components for the optical Kerr effect from precise measurements of the dc Kerr effect and electric field-induced second harmonic generation reported in the literature.¹ Our ellipse rotation measurements and calculations confirm that the nonlinear indices for air are substantially lower than previously reported.² Thus nonlinear refraction over long air paths has less impact on diffraction and frequency conversion in large laser systems than previously believed.

© 1987 Optical Society of America