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The spatial structure of nonparaxial radially polarized fields, propagating from the focal plane of a high-focusing optical system, is analytically characterized by means of certain overall parameters. The procedure is based in a formal analogy with the irradiance-moments framework used for describing paraxial beams. The dependence on the propagation distance from the focal plane is derived for the effective beam width recently defined for this type of vectorial highly focused field. Due to the different behavior of the transverse and longitudinal components of the field, they are investigated in separate ways. We also introduce for this kind of nonparaxial field the concepts of beam waist (plane where the transverse beam size reaches the minimum value) and collimation coefficient (connected with the beam spreading). The suitability of the proposed global description is examined by considering, at each transverse plane, the power-content ratio within a circle whose radius is the beam width. The above results are applied to an illustrative example. © 2011 IOP Publishing Ltd.

New transverse orthogonal axes associated with the beam shape are introduced on the basis of the irradiancemoment formalism that describes the overall spatial structure of partially coherent paraxial beams. We refer to them as the intrinsic axes of the beam. The angle between these axes and the laboratory reference coordinates can be determined from the measurements of the second-order spatial moments of the beam, even although the field amplitude is not analytically known. It has been found that the intrinsic axes remain invariant upon propagation through rotationally symmetric first-order optical systems. Two additional analytical quantities have also been introduced. One of them provides a measure of the beam symmetry, and the other one contains information about the beam rotation under propagation. When the field is referred to the intrinsic axes, these two quantities are shown to reach their extreme values. The results are illustrated by means of an example. © 2011 Springer-Verlag.

On the basis of a formal analogy with the irradiance moments, analytical definitions are proposed for the width of both the transverse and the longitudinal component of rotationally-symmetric radially-polarized fields at the focal plane of a high-focusing optical system. The beam width of the whole field is also introduced. The transverse beam size is thus associated with the overall spatial structure of the field. The beam-width definitions are applied to an illustrative example, which enables us to show that, at the focal plane, the power contained within a circle whose radius is given by the proposed beam widths represents the main part of the total power. © 2010 Optical Society of America.

Within the framework of the angular plane-wave spectrum of the electromagnetic field, the general form is given for the freely-propagating beams, exact solution of the Maxwell equations, that closely approach (in an algebraic sense) to a purely-longitudinal vectorial distribution at some transverse plane. In the rotationally symmetric case, such a field is written as the combination of radial and longitudinal components, whose propagation can be analysed independently. Several illustrative examples are also considered. © Springer-Verlag 2010.

The overall spatial structure of a general partially coherent field is shown to be connected with the cross-correlation between the so-called spiral modes, understood as the terms of the spiral-harmonics series expansion of the field. The formalism based on the beam irradiancemoments is used, and the light field is globally described by the beam width, the far-field divergence, the beam quality factor, the orientation of the beam profile and the angular orbital momentum, given as the sum of its asymmetrical and vortex parts. This overall spatial description is expressed in terms of the intermodal coherence features (cross-correlation between spiral modes). The above analytical results are also illustrated by means of an example. ©2009 Optical Society of America.