Design of multilevel spiral phase Fresnel zone plates
04 Oct 2012-pp 95-96
TL;DR: In this paper, an improved version of the spiral phase Fresnel zone plate (FZP) was proposed to allow for a compact optical configuration for generation of elliptical donut beams.
Abstract: Optical techniques are widely used for trapping of particles. One such technique involves the use of passive diffractive optical elements. Recently, a novel passive diffractive optical element, a spiral phase Fresnel zone plate (FZP) was proposed [1]. In this paper, we present an improved version, of the earlier reported element, that will allow for a compact optical configuration for generation of elliptical donut beams. This compact design enables easy insertion of the device into optical trapping experiments for micro level trapping. The proposed multilevel spiral phase FZP can be used for applications such as trapping by illuminating it with a narrow spectral width laser as shown in Fig. 1(a). The simulated 3-D structure of the proposed multilevel spiral phase FZP is shown in Fig. 1(b).
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TL;DR: In this paper, two kinds of Fresnel zone plates (FZPs) have been employed as optical coupling devices to enhance the response of versatile laser detection systems, and the simulation and experiment results indicate that the FZPs have selective focusing abilities for wavelength and coherence of the incident lights, which contributes to high collection efficiency to the laser signals and suppression to the ambient lights.
Abstract: In this paper, Fresnel zone plates (FZPs) have been employed as optical coupling devices to enhance the response of versatile laser detection systems. Two kinds of FZPs, amplitude-Fresnel zone plate (AFZP) and phase-Fresnel zone plate (PFZP), were fabricated and studied for comparison. The simulation and experiment results indicate that the FZPs have selective focusing abilities for wavelength and coherence of the incident lights, which contributes to high collection efficiency to the laser signals as well as suppression to the ambient lights. A 34 and 26 times gain in response were obtained when illuminated by coherent laser light by applying an AFZP and PFZP to an InGaAs/InP p-i-n photodetector, respectively. And a 30 % reduction in response was achieved by using an AFZP when illuminated by incoherent Tungsten-halogen lamp. In addition, 9.6 times of response enhancement has been observed after utilizing the AFZP for the laser ranging system.
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References
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TL;DR: In this paper, the Huygens-Fresnel-Kirchhoff diffraction integral has been formulated for incident spherical waves with use of the Kirchhoff obliquity factor and the wave front as the surface of integration instead of the aperture plane.
Abstract: The Huygens–Fresnel diffraction integral has been formulated for incident spherical waves with use of the Kirchhoff obliquity factor and the wave front as the surface of integration instead of the aperture plane. Accurate numerical integration calculations were used to investigate very-near-field (a few aperture diameters or less) diffraction for the well-established case of a circular aperture. It is shown that the classical aperture-plane formulation degenerates when the wave front, as truncated at the aperture, has any degree of curvature to it, whereas the wave-front formulation produces accurate results from ∞ up to one aperture diameter behind the aperture plane. It is also shown that the Huygens–Fresnel–Kirchhoff incident-plane-wave-aperture-plane-integration and incident-spherical-wave-wave-front-integration formulations produce equally accurate results for apertures with exit f-numbers as small as 1.
39 citations
"Design of multilevel spiral phase F..." refers methods in this paper
...The multilevel spiral phase FZP is analyzed using standard scalar diffraction formulae [2] and the corresponding simulated intensity profile along the x direction at the focal plane of the FZP is shown in Fig....
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TL;DR: Numerical results show that hollow beams can be generated and can also be controlled by the number of the zones and the topological charge, which implies the potential applications of such kind of zone plate in trapping and manipulating particles.
Abstract: Focusing properties of Fresnel zone plates with spiral phase with integer and fractional topological charges illuminated by plane wave are studied. Numerical results show that hollow beams can be generated and can also be controlled by the number of the zones and the topological charge, which implies the potential applications of such kind of zone plate in trapping and manipulating particles.
31 citations
"Design of multilevel spiral phase F..." refers background or methods in this paper
...Recently, a novel passive diffractive optical element, a spiral phase Fresnel zone plate (FZP) was proposed [1]....
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...The generation of a donut beam is proposed and numerically demonstrated by introducing a spiral phase to either the odd or the even half period zones of the FZP proposed in [1]....
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