TARGET-PLANE INTENSITY APPROXIMATION FOR APERTURED GAUSSIAN BEAMS APPLIED TO HETERODYNE BACKSCATTER LIDAR SYSTEMS

With an application in lidar systems in mind, we investigate the effec ts of transmit-aperture truncation of Gaussian beams by employing the extended Huygens-Fresnel principle. We derive an approximation to the top-hat aperture-transmission function by defining an abstract Gaussia n aperture-transmission function. The two fitting parameters of the la tter are found when the beam radius and the on-axis intensity for both aperture cases are equated in the observation plane. Bounds for the a pplicability of the approximation are established, and its accuracy an d usefulness is demonstrated through application to the calculation of the return signal of a heterodyne lidar system.