Propagation and diffraction of truncated Gaussian beams

The Fresnel diffraction of a truncated Gaussian beam is investigated in detail. Our aim is to provide usable analytical expressions of the diffracted field with respect to the variation of propagation and diffraction parameters. Particular attention is paid to the determination of a trade-off between computing accuracy and simplicity. An illustration of the use of the various expressions describing the beam diffraction and propagation is given for the case of mode coupling in a single-mode fiber.