Abstract

Self-focusing and self-defocusing of a transversely excited atmosphere CO₂ laser pulse in a CH₃F medium are investigated. The self-defocusing effect that was previously reported at the two laser lines 9P(20) and 9P(22) is confirmed, and the self-focusing effect at the 9P(18) line is observed in this experiment for the first time to our knowledge. From the spectral data of CH₃F we find that the self-focusing of the 9P(18) line results from the resonant absorption (J = 13 → J = 14, ν₃ = 0 → ν₃ = 1) in ¹³CH₃F. The nonlinear refractive-index coefficients obtained for the 9P(20), 9P(22), and 9P(18) lines are (−5.5 ± 0.4) × 10⁻¹², (−2.9 ± 0.4) × 10⁻¹², and (+4.2 ± 0.3) × 10⁻¹² cm²/W, respectively.

© 1991 Optical Society of America

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