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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 combination of a grating as a periodic object and a Fresnel zone plate with a quasi-periodic structure leads to some novel array generator elements and it is shown that diffraction performance of the proposed element depends on the grating structure, so that the diffractive performance may efficiently be increased if the grates is replaced with a checkerboard structure.
Abstract: The combination of a grating as a periodic object and a Fresnel zone plate with a quasi-periodic structure leads us to propose some novel array generator elements. It is shown that diffraction performance of the proposed element depends on the grating structure, so that the diffraction performance may efficiently be increased if the grating is replaced with a checkerboard structure. Depending on the kind of zone plate, we have demonstrated that the corresponding array generator is also created. For instance, a focused array of vortices is generated when the zone plate is replaced with a spiral zone plate. We have also clarified that the method allows us to generalize it to the other class of the zone plate-based elements, e.g., a cross zone plate. Namely, when the cross zone plate is used instead of the Fresnel zone plate, a spot array generator is again created whose diffractive performance is improved by modifying its phase structure. Also, it is clearly shown that the focusing feature of the element depends on the grating period. Finally, there is a good agreement between the simulation results and the corresponding experimental works.
17 citations
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TL;DR: In this article, a modified hologram reconstruction mechanism is presented which introduces the single shot capability in Fresnel incoherent correlation holography (FINCH) in inline configuration requires an active phase modulator and at least three camera shots to reconstruct objects without the twin image and bias terms.
Abstract: Fresnel incoherent correlation holography (FINCH) is a self-interference based super-resolution three-dimensional imaging technique. FINCH in inline configuration requires an active phase modulator and at least three camera shots to reconstruct objects without the twin image and bias terms. In this study, FINCH is realized using a randomly multiplexed bifocal binary Fresnel zone lenses fabricated using electron beam lithography. A modified hologram reconstruction mechanism is presented which introduces the single shot capability in FINCH. A point spread hologram library was recorded using a point object located at different axial locations and an object hologram was recorded. The image of the object at different planes were reconstructed using decorrelation of the object hologram by the point spread hologram library. Application potential including bio-medical optics is discussed.
17 citations
TL;DR: It is shown that the propagation of a temporal pulse in a single-mode optical fiber is mathematically equivalent to Fresnel diffraction of a spatial beam.
Abstract: It is shown that the propagation of a temporal pulse in a single-mode optical fiber is mathematically equivalent to Fresnel diffraction of a spatial beam. A time-domain Collett–Wolf equivalence theorem applies to pulse propagation in fibers.
17 citations
TL;DR: In this article, a stable interference ring pattern inside the conical four-photon emission was observed and attributed to the spatial arrangement of small-scale filaments at different distances in the glass.
Abstract: White supercontinuum (SC) produced from Fresnel diffraction was demonstrated in BK7 glasses using femtosecond laser pulses. For input pulse energy below the threshold for the onset of self-focusing and SC generation, an aperture was placed into the beam before the BK7 glass to redistribute the intensity by diffraction along the propagation axis to produce a stable SC. The SC occurred at various distances from the aperture containing odd number of Fresnel zones, mainly the first. This result plays an important role in studying the properties of SC sources as well as the diffraction field distribution. A distinct and stable interference ring pattern inside the conical four-photon emission is observed and attributed to the spatial arrangement of small-scale filaments at different distances in the glass.
17 citations
TL;DR: In this paper, it was shown that a radiating monopole can be described mathematically as two point sources located at each end of the monopole, and a microwave hologram was recorded using liquid crystals which upon optical reconstruction yielded two points as predicted by the theory.
Abstract: Microwave holography is applied to the investigation of the radiation mechanism of a monopole. It is shown that a radiating monopole can be described mathematically as two point sources located at each end of the monopole. A microwave hologram was recorded using liquid crystals which upon optical reconstruction yielded two points as predicted by the theory. Using optical techniques, one can visualize the field at the antenna plane, at a plane in the Fresnel zone, and at a plane in the far field. This technique is, however, only one example of microwave holography in the investigation of a radiator. It can be very useful in designing any type of antenna.
17 citations