The Experts below are selected from a list of 3993 Experts worldwide ranked by ideXlab platform
Francisco Belmar - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Predistortion Techniques on Fresnel Zone Plates in Ultrasound Applications
'MDPI AG', 2021Co-Authors: Jose Miguel Fuster, Sergio Pérez-lópez, Francisco Belmar, Pilar CandelasAbstract:In this work, we analyze the effect of predistortion techniques on the focusing profile of Fresnel Zone Plates (FZPs) in ultrasound applications. This novel predistortion method is based on either increasing or decreasing the width of some of the FZP Fresnel rings by a certain amount. We investigate how the magnitude of the predistortion, as well as the number and location of the predistorted rings, influences the lens focusing profile. This focusing profile can be affected in different ways depending on the area of the lens where the predistortion is applied. It is shown that when the inner area of the lens, closer to its center, is predistorted, this technique allows the control of the focal depth at the main focus. However, when the predistortion is applied to an area farther from the center of the lens, the acoustic intensity distribution among the main focus and the closest adjacent secondary foci can be tailored at a certain degree. This predistortion technique shows great potential and can be used to control, modify and shape the FZP focusing profile in both industrial and therapeutic applications
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on the use of phase correction rings on Fresnel Zone plates with ultrasound piston emitters
Applied Physics Letters, 2018Co-Authors: Sergio Perezlopez, Jose Miguel Fuster, Pilar Candelas, Constanza Rubio, Francisco BelmarAbstract:In this work, the distortion of the Fresnel Zone Plate focusing profile generated by a piston emitter in ultrasound applications is significantly reduced through the use of phase correction rings, which compensate the effect of the piston emitter radiation diagram. Both simulation and experimental results demonstrate the improvement achieved with this design method over the conventional case.In this work, the distortion of the Fresnel Zone Plate focusing profile generated by a piston emitter in ultrasound applications is significantly reduced through the use of phase correction rings, which compensate the effect of the piston emitter radiation diagram. Both simulation and experimental results demonstrate the improvement achieved with this design method over the conventional case.
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on the use of phase correction rings on Fresnel Zone plates with ultrasound piston emitters
Applied Physics Letters, 2018Co-Authors: Sergio Perezlopez, Jose Miguel Fuster, Pilar Candelas, Constanza Rubio, Francisco BelmarAbstract:In this work, the distortion of the Fresnel Zone Plate focusing profile generated by a piston emitter in ultrasound applications is significantly reduced through the use of phase correction rings, which compensate the effect of the piston emitter radiation diagram. Both simulation and experimental results demonstrate the improvement achieved with this design method over the conventional case.
Sergio Perezlopez - One of the best experts on this subject based on the ideXlab platform.
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on the use of phase correction rings on Fresnel Zone plates with ultrasound piston emitters
Applied Physics Letters, 2018Co-Authors: Sergio Perezlopez, Jose Miguel Fuster, Pilar Candelas, Constanza Rubio, Francisco BelmarAbstract:In this work, the distortion of the Fresnel Zone Plate focusing profile generated by a piston emitter in ultrasound applications is significantly reduced through the use of phase correction rings, which compensate the effect of the piston emitter radiation diagram. Both simulation and experimental results demonstrate the improvement achieved with this design method over the conventional case.In this work, the distortion of the Fresnel Zone Plate focusing profile generated by a piston emitter in ultrasound applications is significantly reduced through the use of phase correction rings, which compensate the effect of the piston emitter radiation diagram. Both simulation and experimental results demonstrate the improvement achieved with this design method over the conventional case.
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on the use of phase correction rings on Fresnel Zone plates with ultrasound piston emitters
Applied Physics Letters, 2018Co-Authors: Sergio Perezlopez, Jose Miguel Fuster, Pilar Candelas, Constanza Rubio, Francisco BelmarAbstract:In this work, the distortion of the Fresnel Zone Plate focusing profile generated by a piston emitter in ultrasound applications is significantly reduced through the use of phase correction rings, which compensate the effect of the piston emitter radiation diagram. Both simulation and experimental results demonstrate the improvement achieved with this design method over the conventional case.
Hoi Sing Kwok - One of the best experts on this subject based on the ideXlab platform.
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micro patterned photo aligned ferroelectric liquid crystal Fresnel Zone lens
Optics Letters, 2015Co-Authors: Abhishek Kumar Srivastava, Xiaoqian Wang, Shangqing Gong, Dong Shen, Yanqing Lu, Vladimir G Chigrinov, Hoi Sing KwokAbstract:In this Letter, we disclose a fast switchable Fresnel Zone lens (FZL) by confining the ferroelectric liquid crystals (FLCs) in multiple microscopically defined photo-aligned alignment domains. The photo-alignment (PA) offers good control on the anchoring energy (W) by mean of irradiation doses (ID) and thus excellent alignment for FLCs. Two operational modes of the FLCFZL, i.e., FOCUS/OFF and FOCUS/DEFOCUS, were demonstrated. The proposed diffracting element provides fast response time, high diffraction efficiency (η), with saturated electro-optical (EO) operations up to high frequency (≈2 kHz). Thus, the proposed FLCFZLs with simple fabrication open several opportunities to improve the quality of existing devices and to find new applications.
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liquid crystal Fresnel Zone lens based on single side patterned photoalignment layer
Applied Optics, 2014Co-Authors: Xiaoqian Wang, Abhishek Kumar Srivastava, Vladimir G Chigrinov, Fan Fan, Alwin M W Tam, Hoi Sing KwokAbstract:In this article, we disclose a method to fabricate a liquid crystal (LC) Fresnel Zone lens (FZL) with high efficiency. The LCFZL, based on patterned planar-aligned regions, has been prepared by means of a two-step photoalignment technique. The proposed binary-phase LCFZL manifests 39% diffraction efficiency at the focal point, which is close to the theoretical limit, 41%. Moreover, because of a lower driving voltage and faster response time, these elements could find application in many modern devices.
Constanza Rubio - One of the best experts on this subject based on the ideXlab platform.
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on the use of phase correction rings on Fresnel Zone plates with ultrasound piston emitters
Applied Physics Letters, 2018Co-Authors: Sergio Perezlopez, Jose Miguel Fuster, Pilar Candelas, Constanza Rubio, Francisco BelmarAbstract:In this work, the distortion of the Fresnel Zone Plate focusing profile generated by a piston emitter in ultrasound applications is significantly reduced through the use of phase correction rings, which compensate the effect of the piston emitter radiation diagram. Both simulation and experimental results demonstrate the improvement achieved with this design method over the conventional case.In this work, the distortion of the Fresnel Zone Plate focusing profile generated by a piston emitter in ultrasound applications is significantly reduced through the use of phase correction rings, which compensate the effect of the piston emitter radiation diagram. Both simulation and experimental results demonstrate the improvement achieved with this design method over the conventional case.
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on the use of phase correction rings on Fresnel Zone plates with ultrasound piston emitters
Applied Physics Letters, 2018Co-Authors: Sergio Perezlopez, Jose Miguel Fuster, Pilar Candelas, Constanza Rubio, Francisco BelmarAbstract:In this work, the distortion of the Fresnel Zone Plate focusing profile generated by a piston emitter in ultrasound applications is significantly reduced through the use of phase correction rings, which compensate the effect of the piston emitter radiation diagram. Both simulation and experimental results demonstrate the improvement achieved with this design method over the conventional case.
O V Minin - One of the best experts on this subject based on the ideXlab platform.
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experimental demonstration of square Fresnel Zone plate with chiral side lobes
Applied Optics, 2017Co-Authors: A Vijayakumar, Igor V. Minin, O V Minin, B Vinoth, Joseph Rosen, Chau Jern ChengAbstract:In this study, we introduce what we believe is a novel holographic optical element called a chiral square Fresnel Zone plate (CSFZP). The chirality is imposed on a square Fresnel Zone plate (SFZP) using a nonclassical technique by rotating the half-period Zones relative to one another. The rotation of the half-period Zones, in turn, twists the side lobes of the diffraction pattern without altering the focusing properties inherent to a SFZP. As a consequence, the beam profile is hybrid, consisting of a strong central Gaussian focal spot with gradient force similar to that generated by a lens and twisted side lobes with orbital angular momentum. The optical fields at the focal plane were calculated and found to possess a whirlpool-phase profile and a twisted intensity profile. Analysis of the field variation along the direction of propagation revealed a spiraling phase and amplitude distribution. Poynting vector plot of the fields revealed the presence of angular momentum in the regions of chiral side lobes. The phase of the CSFZPs were displayed on a phase-only reflective spatial light modulator and illuminated using a laser. The intensity patterns recorded in the experiment match the calculated ones, with a strong central focal spot and twisted side lobes. The beam pattern was implemented in an optical trapping experiment and was found to possess particle trapping capabilities.
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Fresnel Zone plate antenna with hexagonal cut Zones
Microwave and Optical Technology Letters, 2008Co-Authors: S M Stoutgrandy, Igor V. Minin, A Petosa, O V Minin, J S WightAbstract:A novel Fresnel Zone plate antenna (FZPA) with hexagonal-cut Zones is presented. This new structure was simulated at 30 GHz using a finite-difference time-domain software to study its gain and sidelobe levels in relation to the standard circular FZPA and the hexagonal FZPA. Several prototypes were built and tested to verify the simulations. It was found that the FZPA with rotated alternating hexagonal-cut Zones provides the ability to control the shape and location of the sidelobes while still maintaining the benefits of the hexagonal shape in terms of array packing. Also, this new structure has an improved sidelobe level over the standard version. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 672–676, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23183
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novel reflector backed Fresnel Zone plate antenna
Microwave and Optical Technology Letters, 2007Co-Authors: S M Stoutgrandy, Igor V. Minin, A Petosa, O V Minin, J S WightAbstract:A novel reflector-backed Fresnel Zone plate antenna (FZPA) is presented. The reflector is positioned at the aperture of the feed antenna such that the radiation that was reflected back off the metal Zones of the FZPA gets reradiated instead of being lost. This structure enhances the directivity of the FZPA by about 1 dB and also improves the sidelobes and aperture efficiency. The other benefit of the structure is that it enables a significant reduction in the volume of the FZPA. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3096–3098, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22946
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improved zoning rule for designing square Fresnel Zone plate lenses
Microwave and Optical Technology Letters, 2007Co-Authors: Igor V. Minin, A Petosa, O V Minin, S ThirakouneAbstract:An improved zoning rule is presented for designing a square Fresnel Zone plate lens (FZPL). This new rule results in a higher gain when the FZPL is used as an antenna element or can enhance the focusing properties of the square FZPL when used to collimate an incident plane wave. The derivation of this improved zoning rule is presented along with simulated results for some typical cases. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 276–278, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22108
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array of Fresnel Zone plate lens antennas circular hexagonal with chiral symmetry and hexagonal boundary
Joint International Conference on Infrared Millimeter Waves and International Conference on Teraherz Electronics, 2006Co-Authors: Igor V. Minin, O V MininAbstract:A novel hexagonal Fresnel Zone plate antenna with chiral beampattern is introduced and compared to the traditional circular Fresnel Zone plate antenna. The hexagonal geometry is better suited for arrays and provides the ability to both improve the sidelobe level and shift the sidelobe location away from boresight.
