Besinc Pseudo-Schell Model Sources with Circular Coherence

Abstract

Partially coherent sources with non-conventional coherence properties present unusual behaviors during propagation, which have potential application in fields like optical trapping and microscopy. Recently, partially coherent sources exhibiting circular coherence have been introduced and experimentally realized. Among them, the so-called pseudo Schell-model sources present coherence properties that depend only on the difference between the radial coordinates of two points. Here, the intensity and coherence properties of the fields radiated from pseudo Schell-model sources with a degree of coherence of the besinc type are analyzed in detail. A sharpening of the intensity profile is found for the propagated beam by appropriately selecting the coherence parameters. As a possible application, the trapping of different types of dielectric nanoparticles with this kind of beam is described.

Propagation features of a class of beams radiated from pseudo-Schell model vectorial sources

“…It can be demonstrated that the electromagnetic degree of coherence depends on the angular variables through the square of cosine functions, so it shows a periodic behaviour with π period. It is worth noting that this behaviour is dierent from that observed for scalar pseudo Schellmodel beams where the degree of coherence present a circular symmetry [7,8]. The radial dependence of the electromagnetic degree of coherence [22] shows a maximum for points on the same circle but this maximum has not to be necessarily 1, even though this parameter is calculated for the eld at the same point (see Fig.…”

“…(1) where r j = (r j , θ j ) (with j = 1, 2) are the polar coordinates of two points across the source plane. W P S (r 1 , r 2 ) is a scalar cross-spectral density (CSD) of the Gaussian pseudo-Schell model type [7,8], i.e.,…”

“…The interest for such beams lies in the peculiar properties that they may present, both across the source plane and upon propagation. Just to quote some of them, we recall the self-focusing, particle trapping, or propagation through turbulent media [915] A recently introduced example of structured sources in the scalar realm are the so-called pseudo-Schell model (PSM) sources [7,8], which present coherence characteristics that only depend on the dierence of the radial distance to the center of two points in the source transverse section, i.e., on the dierence of their radial coordinates. Vectorial PSM (VPSM) sources have also been proposed by Hyde [16] who, in addition, presented a scheme aimed at synthesizing them.…”

Modal Analysis of Pseudo-Schell Model Sources

“…More general sources, though, can be envisaged with different behaviors of the correlation function. In particular, since their coherence properties affect the features of the radiated beam [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], this opens a new way to searching for particular light sources that best fit for specific applications, such as particle trapping [12,19], free space optical communications [20,21], or sub-Rayleigh imaging [22][23][24][25], among others.…”

“…Here we deal with a wide class of nonconventionally correlated partially coherent sources, the so called pseudo-Schell model sources [11] that are characterized by a degree of coherence that depends only on the difference of the radial coordinates between the involved points. The cross-spectral density (CSD) of the fields produced by such sources was found to possess several peculiar properties [11,12].…”