Pseudo-guide wave propagation in stratified, inverted temperature distributions in the atmosphere

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Conference Proceeding

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We have developed a theoretical model and a simulation model of wave propagation through stratified, inverted temperature distributions in the atmosphere. These conditions are present when local weather conditions cause a warm layer of air to exist above a cool layer of air, rather than the more common situation at low altitude, where the air temperature gradually decreases with increasing altitude. In this situation a sort of guided wave propagation is possible for laser beams. The ray describing the beam propagation direction is found to follow a path through the inverted layer similar to the path a guided ray follows through a gradient-index optical fiber, but without the phase matching condition being satisfied in general, leading to our use of the term pseudo-guided wave for this propagation phenomenon. For the temperature inversion to exist, it is necessarily the case that the vertical component of the wind must be very weak, and we conjecture that as a result the turbulence is quite weak in this layer, and possibly anisotropic. In this paper we describe this phenomenon, and establish the realistic nature of the phenomenon by examining real vertical temperature profiles. Ray optics and wave optics propagators are used to show that propagation through these layers leads to much higher beam quality at a target plane than would be expected under more typical atmospheric conditions. We also use the measured vertical temperature profiles to show that these conditions are quite common. © 2014 IEEE.

Publication Title

IEEE Aerospace Conference Proceedings