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Taco D Visser

Publications and source records attributed to Taco D Visser.

10 recordsLinked to original sources
PubMed2006

Scattering of light from quasi-homogeneous sources by quasi-homogeneous media.

The field generated by scattering of light from a quasi-homogeneous source on a quasi-homogeneous, random medium is investigated. It is found that, within the accuracy of the first-order Born approximation, the far field satisfies two reciprocity relations (sometimes called uncertainty relations). One of them implies that the spectral density (or spectral intensity) is proportional to the convolution of the spectral density of the source and the spatial Fourier transform of the correlation coefficient of the scattering potential. The other implies that the spectral degree of coherence of the far field is proportional to the convolution of the correlation coefficient of the source and the spatial Fourier transform of the strength of the scattering potential. While the case we consider might seem restrictive, it is actually quite general. For instance, the quasi-homogeneous source model can be used to describe the generation of beams with different coherence properties and different angular spreads. In addition, the quasi-homogeneous scattering model adequately describes a wide class of turbulent media, including a stratified, turbulent atmosphere and confined plasmas.

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PubMed2005

On the wavefront spacing of focused, radially polarized beams.

We analyze the phase behavior of strongly focused, radially polarized electromagnetic fields. It is shown that, under certain circumstances, the spacing between successive wavefronts can be either greater or smaller than that of a plane wave of the same frequency. Also, this spacing can be significantly larger than that which is predicted for a linearly polarized field that is focused by the same system.

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PubMed2004

Connection between phase singularities and the radiation pattern of a slit in a metal plate.

We report a new fundamental relation between the minima of the far-zone radiation pattern of a narrow slit in a metal plate and the location of phase singularities in the intermediate field. If a system parameter such as the wavelength is changed, a previously unappreciated singular optics phenomenon occurs: namely, the transition of a near-zone phase singularity into a singularity of the radiation pattern. Our results have significance for the design of novel nanoscale light sources and antennas.

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PubMed2004

Spatial correlation properties of focused partially coherent light.

We investigate the spatial coherence properties in the focal region of a converging, spatially partially coherent wave field. In particular, we find that, depending on the effective coherence length of the field in the aperture, the longitudinal and transverse coherence lengths in the focal region can be either larger or smaller than the corresponding width of the intensity distribution. Also, the correlation function is shown to exhibit phase singularities.

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PubMed2003

Can spatial coherence effects produce a local minimum of intensity at focus?

It is demonstrated that, for high-Fresnel-number focusing systems illuminated by certain classes of partially coherent light, it is possible to produce a local minimum of intensity at the geometrical focus. Such an effect is possible even though the average intensity in the entrance plane of the lens is uniform. An explanation is offered for this effect, and potential applications are considered.

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PubMed2003

New effects in Young's interference experiment with partially coherent light.

We analyze the coherence properties of a partially coherent optical field emerging from two pinholes in a plane opaque screen. We show that at certain pairs of points in the region of superposition the light is fully coherent, regardless of the state of coherence of the light at the pinholes. In particular, this result also holds if each pinhole is illuminated by a different laser.

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PubMed2003

Phase singularities of the coherence functions in Young's interference pattern.

We analyze the coherence properties of a partially coherent field emerging from two pinholes in an opaque screen and show that the spectral degree of coherence possesses phase singularities on certain surfaces in the region of superposition. To our knowledge, this is the first illustration of the singular behavior of the spectral degree of coherence, and the results extend the field of singular optics to the study of phase singularities of correlation functions.

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PubMed2003

Light transmission through a subwavelength slit: waveguiding and optical vortices.

The anomalous (i.e., more than 100%) light transmission through a subwavelength slit in a thin metal plate is accompanied by a combination of waveguiding and phase singularities of the field of power flow near the slit. The crucial role of these phase singularities (such as optical vortices and saddle points) in exciting the waveguide modes is systematically studied. We predict transmission efficiencies as high as 300% for certain configurations.

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PubMed2002

Singular behavior of the spectrum in the neighborhood of focus.

In a recent paper [Phys. Rev. Lett. 88, 013901 (2002)] it was shown that when a convergent spatially coherent polychromatic wave is diffracted at an aperture, remarkable spectral changes take place on axis in the neighborhood of certain points near the geometrical focus. In particular, it was shown that the spectrum is red-shifted at some points, blueshifted at others, and split into two lines elsewhere. In the present paper we extend the analysis and show that similar changes take place in the focal plane, in the neighborhood of the dark rings of the Airy pattern.

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