Topic
Fresnel zone
About: Fresnel zone is a research topic. Over the lifetime, 2337 publications have been published within this topic receiving 37650 citations.
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TL;DR: The basic conclusion is that rectangular aperture unstable resonators are quite insensitive to misalignment, in the sense that the lowest-loss mode continues to be essentially diffraction limited as long as the feedback mirror remains well within the output beam.
Abstract: A previously developed technique for the calculation of modes of perfectly aligned unstable resonators in the limit of large Fresnel number is here extended to include effects of misalignment. It is shown how asymptotic techniques may be employed to simplify the calculation of near- and far-field patterns produced by such modes. The basic conclusion is that rectangular aperture unstable resonators are quite insensitive to misalignment, in the sense that the lowest-loss mode continues to be essentially diffraction limited as long as the feedback mirror remains well within the output beam.
44 citations
TL;DR: In this paper, an approximate analysis of VLF propagation in the earth-ionosphere waveguide of variable height is given, and it is shown that ionospheric perturbations lying within the first Fresnel zone are most effective in modifying the phase of the received signal.
Abstract: An approximate analysis is given for VLF propagation in the earth-ionosphere waveguide of variable height. The height changes are not restricted to points along the great circle path connecting the transmitter and receiver. By choosing a simple example, we show that ionospheric perturbations lying within the first Fresnel zone are most effective in modifying the phase of the received signal. This paper is a sequel to an earlier one published in the Journal in 1961 about ionospheric depressions that were infinite in their transverse dimension.
44 citations
TL;DR: In this paper, a high repetition rate femtosecond laser system is combined with a spatial light modulator (SLM) for diffractive multiple beam processing, and the effect of the zero order beam is eliminated by adding a Fresnel zone lens to defocus the undiffracted beam at the processing plane.
44 citations
TL;DR: The presented double-sided zone plates with 30 nm smallest zone width offer up to 9.9% focusing efficiency at 9 keV, that results in a factor of two improvement over their previously demonstrated single-sided counterparts.
Abstract: The fabrication of high aspect ratio metallic nanostructures is crucial for the production of efficient diffractive X-ray optics in the hard X-ray range We present a novel method to increase their structure height via the double-sided patterning of the support membrane In transmission, the two Fresnel zone plates on the two sides of the substrate will act as a single zone plate with added structure height The presented double-sided zone plates with 30 nm smallest zone width offer up to 99% focusing efficiency at 9 keV, that results in a factor of two improvement over their previously demonstrated single-sided counterparts The increase in efficiency paves the way to speed up X-ray microscopy measurements and allows the more efficient utilization of the flux in full-field X-ray microscopy
44 citations
TL;DR: It is shown that, although Abbe's sine law applies to zone plates but not to Fresnel lenses, both can yield single-element aplanats if formed on a curved surface.
Abstract: The generalization of zone plates and Fresnel lenses from the usual flat surfaces to curved surfaces is discussed. It is shown that, although Abbe's sine law applies to zone plates but not to Fresnel lenses, both can yield single-element aplanats if formed on a curved surface. Third-order aberration formulas are given.
43 citations