Julio Serna

Parametric characterization of general partially coherent beams propagating through ABCD optical systems

Within the formalism of the Wigner distribution function, a new parameter is proposed, which characterizes arbitrary tridimensional partially coherent beams and is invariant through ABCD optical systems. The relationship between such a parameter and the bidimensional concept of beam quality is analyzed. An absolute lower bound that the new parameter can reach is also shown.

Complete spatial characterization of a pulsed doughnut-type beam by use of spherical optics and a cylindrical lens

A complete spatial characterization (in second-order moments) of a doughnut-type beam from a pulsed transversely excited atmospheric CO2 laser is described. It includes the measurement of the orbital angular momentum carried by the beam. The key element in the characterization is the use of a cylindrical lens in addition to the usual spherical optics. Internal features of the beam that would have remained hidden if only spherical optics were employed were revealed by use of the cylindrical lens. The experimental results are compared and agree with a theoretical Laguerre-Gauss mode beam.

Beam quality dependence on the coherence length of Gaussian Schell-model fields propagating through ABCD optical systems

The quality behaviour of Gaussian Schell-model fields propagating through general (non-orthogonal) ABCD optical systems has been characterized by introducing a number of parameters. Such parameters have been given in terms of the Wigner distribution function of the field, closely connected with its second-order coherence features. Dependence of the focusing capabilities, transversal widths and beam asymmetry on the coherence length of the field has been investigated.Abstract The quality behaviour of Gaussian Schell-model fields propagating through general (non-orthogonal) ABCD optical systems has been characterized by introducing a number of parameters. Such parameters have been given in terms of the Wigner distribution function of the field, closely connected with its second-order coherence features. Dependence of the focusing capabilities, transversal widths and beam asymmetry on the coherence length of the field has been investigated.

Rotation of partially coherent beams propagating through free space

The orientation of a general partially coherent beam is described by introducing two pairs of orthogonal axes defined in terms of the second-order coherence features of the field. A general classification scheme for light beams is presented, based on their rotational behaviour under free propagation. This behaviour could be inferred from the values of certain measurable parameters at some plane. As an example of interest, the above classification is applied to Gaussian (coherent) beams with general astigmatism.

On the paramtric characterization of the transversal spatial structure of laser pulses

Abstract From the application of a simple analytical model to describe a laser pulse, the transversal spatial structure of the pulse amplitude is linked to its (measurable) second-order intensity moments, integrated along the pulse duration. These formulae are applied to some examples. The experimental values correspond to TEA CO 2 laser pulses, for which the dependence of the beam quality on the presence of nitrogen in the gas mixture and also on the size of an intracavity diaphragm has also been investigated.

Beam quality changes of Gaussian Schell-model fields propagating through Gaussian apertures

Beam quality behavior of Gaussian Schell-model beams that propagate through Gaussian apertures is analyzed.

Beam quality in monomode diode lasers

An analytic and measurable beam parameter is defined for beams emerging from heterojunction monomode diode lasers with very thin active layers, which provides a joint description of their focusing capabilities and far field divergence behaviour. This parameter can be of use as a figure of merit to compare either the output responses of this type of laser or the different optical systems employed to modify the laser beam. The minimum value of this parameter is determined. Also, it is shown that the beams emitted by these lasers cannot be transformed into circularly symmetric ones by anyABCD optical system. Finally, the possibility of achieving circularly symmetric intensities (at least to second order) and/or beam collimation at some plane is investigated, and its connection with the coupling efficiency between a monomode diode laser and an optical fibre is pointed out.

Quality changes of beams propagating through super-Gaussian apertures

Beam quality behavior of Hermite-Gauss modes and Gauss Schell-model fields propagating through super-Gaussian apertures are analyzed.

Time-resolved spatial structure of TEA CO2 laser pulses

The evolution of the intensity profile of TEA CO2 laser pulses along the pulse length is investigated both analytically and experimentally. A simple scalar model of the pulse amplitude is introduced, which gives the loaded-cavity modes as a linear combination of bidimensional Hermite-Gauss functions. According to this model a number of equations are derived which link the time-varying spatial structure of the pulse to its time-resolved second-order intensity moments, namely, the beam width and the M2 parameter.

Parametric characterization of Hermite-Gauss mode beams and Gauss Schell-model fields propagating through super-Gaussian apertures

The influence of super-Gaussian apertures on the beam power, beam size, beam quality factor and kurtosis parameter of Hermite-Gauss mode beams and Gauss Schell-model fields is investigated in detail.