Optimum Truncation of a Gaussian Beam for Propagation Through Atmospheric Turbulence.
AEROSPACE CORP EL SEGUNDO CA TECHNOLOGY OPERATIONS
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We consider the mean on-axis far-field or focal-plane irradiance of a Gaussian Beam truncated by a circular aperture in the presence of atmospheric turbulence. In the absence of turbulence, we present an accurate analytic approximation for the irradiance distribution that is valid within the main central lobe of the beam. Based on this approximation, we then obtain the mean on-axis far-field irradiance and corresponding turbulence Strehi ratio for the truncated Gaussian beam. By maximizing the on-axis irradiance, we obtain the optimum ratio of the beam diameter to the aperture diameter in the presence of turbulence and present results for the corresponding maximum on-axis irradiance as a function of the strength of turbulence. In particular, for Dr sub 0 1, where D is the aperture diameter, and r sub 0 is Frieds coherence length, optimum truncation of a Gaussian beam and uniform illumination of a circular aperture where the same total power is uniformly distributed over the aperture result in the same on-axis irradiance in the presence of uncompensated turbulence. AN
- Lasers and Masers