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Flat lens imaging does not need negative refraction  [PDF]
Chao-Hsien Kuo,Zhen Ye
Physics , 2003,
Abstract: In a recent communication, Parimi et al. (Nature 426, 404 (2003)) reported the experimental results on imaging by a flat lens made of photonic crystals. They attributed the observed focusing to the negative refraction expected for the Left-Handed-Materials (LHMs). Here we demonstrate that the experimental observation is irrelevant to the negative refraction of LHMs. Rather, the phenomenon is a natural result of the anisotropic scattering by an array of scatterers.
Sub-wavelength imaging with a left-handed material flat lens  [PDF]
Michael W. Feise,Yuri S. Kivshar
Physics , 2004, DOI: 10.1016/j.physleta.2004.11.031
Abstract: We study numerically, by means of the pseudospectral time-domain method, the unique features of imaging by a flat lens made of a left-handed metamaterial that possesses the property of negative refraction. We confirm the earlier finding that a left-handed flat lens can provide near-perfect imaging of a point source and a pair of point sources with clear evidence of the sub-wavelength resolution. We illustrate the limitation of the resolution in the time-integrated image due to the presence of surface waves.
The application of dynamic scanning in target detection and imaging based on an NR-PC flat lens
WenJuan Meng,Hui Cao,TingGen Shen,FeiFei Wang,ZhengHua Li,BaoGuo Yuan,Ming Huang,YingFei Lian
Chinese Science Bulletin , 2011, DOI: 10.1007/s11434-010-4334-6
Abstract: In this paper a finite-difference time-domain method is used to model and analyze the application of dynamic scanning in target detection and imaging by using an effective negative-refraction photonic crystal (NR-PC) flat lens. The results show that there is a transmission peak, with a value far greater than unity, resulting from the influence of mini-forbidden bands and resonance excitation effect at a resonance frequency of 0.3068(a/λ). Thus, the lightwave emitted from the point source will provide strong backscattered waves after being focused on the target by the NR-PC lens that greatly improves the refocusing resolution and imaging resolution of the backscattered wave. Furthermore, a comparison with a non-dynamic scanning scheme clearly demonstrates that the dynamic scanning scheme provides improved refocusing resolution. In conclusion, our investigation optimized the performance of a detection and imaging system, and provided the basis for converting an idealized LHM lens into a physically realizable NR-PC flat lens.
Impacts of Refraction Index Mismatch on Performance of Target Detection and Imaging by Using Flat LHM Lens
FANG Jie-Ran,GONG Yu,DONG Xiao-Ting,WANG Gang,

中国物理快报 , 2008,
Abstract: Refraction index mismatch between flat left-handed metamaterial (LHM) lens and its surrounding medium generally destroys the focusing of flat LHM lens and degrades the performance of near-field target detection by using flat LHM lens. For LHM lens of refraction index mismatch within ±30%, numerical simulations demonstrate that lenses with large refraction index may suffer less resolution degradation than lenses with small refraction index, and the enhancement of refocused microwave backscattered from target can be subsided by up to approximately 5.5dB. The refraction index mismatch will also shift the target position in the reconstructed image so that theoretical prediction of target position needs to be modified.
Some electronic and optical properties of self-assembled quantum dots: asymmetries in a lens domain  [PDF]
Arezky H. Rodríguez,L. Meza-Montes
Physics , 2005, DOI: 10.1002/pssb.200541365
Abstract: The self-assembled quantum dot with lens domain has rotational symmetry but it is intrinsically asymmetric when the electron moves perpendicularly to its circular base, {\it i. e.} along the rotational axis. To characterize this asymmetry, an external electric field is applied along the positive or negative direction of the rotational axis. We report the different Stark shifts appearing in the spectra as a function of the field intensity for different lens domains. It is shown that for a flat lens domain the asymmetry effects decrease, but even for very flat lenses they can not be approximated by a cylindrical domain. Finally, some optical properties such as the dielectric constant and electroabsorption are studied. Signatures of the energy spectrum reveal in these quantities. The importance of considering the proper lens domain as long as the magnitude and direction field to tune a specific level transition is stressed.
Far Field Imaging Research Based on Multilayer Positive- and Negative-Refractive-Index Media Under Off-Axis Illumination
Pengfei Cao;Xiaoping Zhang;Lin Cheng;Qingqing Meng
PIER , 2009, DOI: 10.2528/PIER09092801
Abstract: In this work, a far field imaging model based on the array structure of positive- and negative-refractive-index media and modulation subwavelength-gratings is firstly presented and is named as the multilayer far field superlens (MLFSL). This new lens is capable of producing optical images by enhancing evanescent waves to the far field. The principle of MLFSL is discussed in detail, and the necessary and sufficient condition for designing MLFSL is obtained. Simultaneously, off-axis illumination technology is introduced to MLFSL system to further improve super-resolution, and the transfer matrix which contains the incidence angles is obtained. The results demonstrate that, compared with other far field superlens, the subwavelength resolution of MLFSL has been enhanced. Such remarkable imaging capability of MLFSL promises new potential for nanoscale imaging and lithography.
Flat Lens Criterion by Small-Angle Phase  [PDF]
Peter Ott,Mohammed H. Al Shakhs,Henri J. Lezec,Kenneth J. Chau
Physics , 2015,
Abstract: We show that a classical imaging criterion based on angular dependence of small-angle phase can be applied to any system composed of planar, uniform media to determine if it is a flat lens capable of forming a real paraxial image and to estimate the image location. The real paraxial image location obtained by this method shows agreement with past demonstrations of far-field flat-lens imaging and can even predict the location of super-resolved images in the near-field. The generality of this criterion leads to several new predictions: flat lenses for transverse-electric polarization using dielectric layers, a broadband flat lens working across the ultraviolet-visible spectrum, and a flat lens configuration with an image plane located up to several wavelengths from the exit surface. These predictions are supported by full-wave simulations. Our work shows that small-angle phase can be used as a generic metric to categorize and design flat lenses.
Dielectric Optical-Controlled Magnifying Lens by Nonlinear Negative Refraction  [PDF]
Jianjun Cao,Ce Shang,Yuanlin Zheng,Xianfeng Chen,Xiaogan Liang,Wenjie Wan
Physics , 2014,
Abstract: A simple optical lens plays an important role for exploring the microscopic world in science and technology by refracting light with tailored spatially varying refractive index. Recent advancements in nanotechnology enable novel lenses, such as, superlens, hyperlens, Luneburg lens, with sub-wavelength resolution capabilities by specially designing materials' refractive indices with meta-materials and transformation optics. However, these artificially nano/micro engineered lenses usually suffer high losses from metals and are highly demanding in fabrication. Here we experimentally demonstrate for the first time a nonlinear dielectric magnifying lens using negative refraction by degenerate four-wave mixing in a plano-concave glass slide, obtaining magnified images. Moreover, we transform a nonlinear flat lens into a magnifying lens by introducing transformation optics into nonlinear regime, achieving an all-optical controllable lensing effect through nonlinear wave mixing, which may have many potential applications in microscopy and imaging science.
Subwavelength imaging with opaque left-handed nonlinear lens  [PDF]
Alexander A. Zharov,Nina A. Zharova,Ilya V. Shadrivov,Yuri S. Kivshar
Physics , 2004, DOI: 10.1063/1.2034114
Abstract: We introduce the concept of subwavelength imaging with an opaque nonlinear left-handed lens by generating the second-harmonic field. We consider a slab of composite left-handed metamaterial with quadratic nonlinear response and show that such a flat lens can form, under certain conditions, an image of the second-harmonic field of the source being opaque at the fundamental frequency.
Actively tunable plasmonic lens for subwavelength imaging at different wavelengths  [PDF]
Beibei Zeng,Haofei Shi,Xiangang Luo
Physics , 2011,
Abstract: A type of tunable plasmonic lens with nanoslits is proposed for subwavelength imaging in the far field at different wavelengths. The nanoslits array in the plasmonic lens, which have constant depths but varying widths, could generate desired optical phase retardations based on the particular propagation property of the Surface Plasmon Polaritons (SPPs) in the metal-dielectric-metal (MDM) slit waveguides. We theoretically and numerically demonstrate the tunability of a single plasmonic lens for subwavelength imaging (full width at half maximum, 0.37 ~0.47) by adjusting the surrounding dielectric fluid, thereby realizing the compact in-plane tunable plasmonic lens. This work provides a novel approach for developing integrative tunable plasmonic lens for a variety of lab-on-chip applications.
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