Shirong Luo

Beam propagation factor of hard-edge diffracted cosh-Gaussian beams

Abstract Based on a generalized truncated second-order irradiance moments definition, an analytical generalized beam propagation factor ( M G 2 -factor) of hard-edge diffracted cosh-Gaussian beams is derived and illustrated numerically. It is shown that the advantage of the method is its consistency with the previous results. The relevant subjects of truncated beams are also discussed.

Propagation of flattened Gaussian beams with rectangular symmetry passing through a paraxial optical ABCD system with and without aperture

The propagation of flattened Gaussian beams (FGBs) passing through a paraxial optical ABCD system has been studied in detail, where both unapertured and apertured cases have been considered. For the unapertured case, a closed-form propagation expression has been derived, and for the apertured case typical numerical examples have been given to illustrate our results and method.

Approximate propagation equations of flattened gaussian beams passing through a paraxial ABCD system with hard-edge aperture

Abstract The propagation of flattened Gaussian beams through a paraxial optical ABCD system with hard-edge aperture is studied. Approximate closed-form equations of FGBs for the apertured case are derived by means of the expansion of the circ function into a finite sum of complex Gaussian functions. The advantages of the method as compared with the straightforward integration of the Collins formula are discussed and illustrated with numerical examples.

Far-field intensity distribution, M2 factor, and propagation of flattened Gaussian beams.

Explicit expressions for the M(2) factor and field distribution of flattened Gaussian beams that propagate through an unapertured paraxial ABCD system are derived and illustrated with numerical examples. We show that the far-field expression of flattened Gaussian beams can be readily obtained by use of our results.

Propagation of three-dimensional flattened Gaussian beams

The concept of flattened Gaussian beams (FGBs) has been extended to the three-dimensional (3D) case, and their propagation properties have been studied in detail for both apertured and unapertured cases. In addition, some special cases only for 3D FGBs, for example, the transformation of a 3D asymmetric FGB into a symmetric one, have been discussed.

The beam quality of annular lasers and related problems

Abstract A detailed study of the beam quality of annular lasers, for example, lasers with or without phase distortions emitted from unstable resonators, is made, where the power in the bucket (PIB) and β-parameter are chosen as criteria for characterizing the beam quality in the far field. It is shown that better focusability is achieved at the real focal plane rather than at the geometrical focal plane due to the focal shift, and the negative quartic phase distortions may improve the beam quality measured in terms of the PIB and/or β-parameter. From a practical point of view the PIB and β can be chosen as beam quality characteristic parameters for such lasers. However, some related problems remain, which are discussed briefly.

A further comparative study of flattened gaussian beams and super-Gaussian beams

Abstract A further comparison between flattened Gaussian beams (FGBs) and super-Gaussian beams (SGBs) is performed. It is shown that the two FGB and SGB having the same beam propagation factor (M2−factor) but different waist widths demonstrate a similar irradiance profile at the position of the equal generalized Fresnel number, while they propagate through a paraxial ABCD system. Furthermore, the focusing by a spherically aberrated lens is studied, and nearly the same propagation characteristics are achieved for the two FGB and SGB with the same M2−factor and waist width.

The pointing stability of flattened Gaussian beams

Based on the moment characterization of the beam pointing stability proposed by Morin et al., the pointing stability of flattened Gaussian beams (FGBs) is studied. The analytical expression for the misalignment factor of FGBs is derived and a comparison with the approximate result is made. The effect of relative transverse and angular shifts on the misalignment factor is analysed. The validity of the exact and approximate expressions is discussed with illustrative numerical examples. The pointing stability of Gaussian beams and truncated plane waves is also studied, and treated as the spatial cases of FGBs.

Improving the accuracy in retrieving particle size distribution using multi-wavelength scattering

A proposal is reported for improving accuracy when retrieving particle size distributions based on light scattering. The method uses a multi-wavelength incident beam combined with the selection of appropriate detection angles. The validity of this method is verified through computer simulation.

Beam quality of annular lasers

The power in the bucket (PIB) and (beta) -parameter are chosen as criteria for characterizing the laser beam quality in the far field, the beam quality of annular lasers with or without phase distributions is studied in detail. It is shown that the better focusability is achieved at the real focal plane, and a suitable choice of negative phase distributions may improve the beam quality.