Diffraction of a Gaussian beam through a finite aperture lens and the resulting heterodyne efficiency

The diffraction field of a Gaussian beam through a finite aperture lens is investigated. The field distributions at the position where the field is most focused are shown and compared with those obtained by an infinite aperture lens. The results are applied to an optical heterodyne detection system with Gaussian fields, and the optimum conditions that maximize the heterodyne efficiency are obtained numerically.