Abstract

We report the first observation of parametric gain suppression of stimulated rotational Raman scattering (SRRS) in atmospheric N₂ in propagation experiments over long air paths with a large-aperture large-Fresnel-number beam. We previously reported our observations of small-scale beam breakup in the near field and high-divergence speckle in the far field in strong SRRS conditions.¹ In our most recent data this speckle is absent in a far-field zone surrounding the forward direction and appears in a narrow cone peaked at an angle of ~300 μrad. We believe this is a manifestation of Raman gain suppression.

© 1988 Optical Society of America