Optimization-free approach for generating sub-diffraction quasi-non-diffracting beams.
TL;DR: An optimization-free design approach is proposed and the possibility of generating sub-diffraction quasi-non-diffracting beams with sub-wavelength size for different polarizations by a binary-phase Fresnel planar lens is demonstrated.
Abstract: Sub-diffraction quasi-non-diffracting beams with sub-wavelength transverse size are attractive for applications such as optical nano-manipulation, optical nano-fabrication, optical high-density storage, and optical super-resolution microscopy. In this paper, we proposed an optimization-free design approach and demonstrated the possibility of generating sub-diffraction quasi-non-diffracting beams with sub-wavelength size for different polarizations by a binary-phase Fresnel planar lens. More importantly, the optimization-free method significantly simplifies the design procedure and the generation of sub-diffracting quasi-non-diffracting beams. Utilizing the concept of normalized angular spectrum compression, for wavelength λ0 = 632.8 nm, a binary-phase Fresnel planar lens was designed and fabricated. The experimental results show that the sub-diffraction transverse size and the non-diffracting propagation distances are 0.40λ0–0.54λ0 and 90λ0, 0.43λ0–0.54λ0 and 73λ0, and 0.34λ0–0.41λ0 and 80λ0 for the generated quasi-non-diffracting beams with circular, longitudinal, and azimuthal polarizations, respectively.
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TL;DR: Recent developments in optical ‘superoscillation’ technologies are reviewed, which aim to overcome current limitations in superresolution techniques requiring contact with the observed object, the use of fluorescent labels, or viewing that is restricted to the near-field of a lens.
Abstract: The resolution of conventional optical elements and systems has long been perceived to satisfy the classic Rayleigh criterion. Paramount efforts have been made to develop different types of superresolution techniques to achieve optical resolution down to several nanometres, such as by using evanescent waves, fluorescence labelling, and postprocessing. Superresolution imaging techniques, which are noncontact, far field and label free, are highly desirable but challenging to implement. The concept of superoscillation offers an alternative route to optical superresolution and enables the engineering of focal spots and point-spread functions of arbitrarily small size without theoretical limitations. This paper reviews recent developments in optical superoscillation technologies, design approaches, methods of characterizing superoscillatory optical fields, and applications in noncontact, far-field and label-free superresolution microscopy. This work may promote the wider adoption and application of optical superresolution across different wave types and application domains.
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25 Oct 2021
TL;DR: In this article, the authors review the fundamental properties of super-oscillatory optical fields and examine emerging technological applications, and discuss advances in imaging and metrology with superoscillatorial light that, in combination with artificial intelligence, offer deeply subwavelength optical resolution.
Abstract: Optical superoscillations are rapid, subwavelength spatial variations of the intensity and phase of light, occurring in complex electromagnetic fields formed by the interference of several coherent waves. The discovery of superoscillations stimulated a revision of the limits of classical electromagnetism — in particular, the studies of phenomena such as unlimitedly small energy hotspots, phase singularities, energy backflow, anomalously high wavevectors and their intriguing similarities to the evanescent plasmonic fields on metals. In recent years, the understanding of superoscillatory light has led to the development of superoscillatory lensing, imaging and metrology technologies. Dielectric, metallic and metamaterial nanostructured superoscillatory lenses have been introduced that are able to create hotspots smaller than allowed by conventional lenses. Far-field, label-free, non-intrusive deeply subwavelength super-resolution imaging and metrology techniques that exploit high light localization and rapid variation of phase in superoscillatory fields have also been developed, including new approaches based on artificial intelligence. We review the fundamental properties of superoscillatory optical fields and examine emerging technological applications. Optical superoscillations are rapid spatial variations of the intensity and phase of light. This Review describes technologies for generating superoscillatory hotspots and discuss advances in imaging and metrology with superoscillatory light that, in combination with artificial intelligence, offer deeply subwavelength optical resolution.
24 citations
TL;DR: In this paper, a superoscillatory optical device has been used to focus cylindrically polarized waves in order to study the properties of super-oscillated optical devices.
Abstract: Superoscillatory optical devices have been widely investigated in the past several years. Due to their unique focusing properties, the ones that focus cylindrically polarized waves are attractive f...
21 citations
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TL;DR: The axicon autocollimator as discussed by the authors is a projector which projects a straight line of images into space, and it can be used to determine the perpendicularity of a mirror.
Abstract: A search for a universal-focus lens has led to a new class of optical elements. These are called axicons. There are many different kinds of axicons but probably the most important one is a glass cone. It may be either transmitting or reflecting. Axicons form a continuous straight line of images from small sources.One application is in a telescope. The usual spherical objective is replaced by a cone. This axicon telescope is in focus for targets from a foot or so to infinity without the necessity of moving any parts. It can be used to view simultaneously two or more small sources placed along the line of sight.If a source of light is suitably added to the telescope it becomes an autocollimator. Like ordinary autocollimators it can be used to determine the perpendicularity of a mirror. In addition, it can simultaneously act as a telescope for a point target which may be an illuminated pinhole in the mirror.The axicon autocollimator is also a projector which projects a straight line of images into space.
956 citations
TL;DR: In this article, a high-numerical-aperture lens is used to achieve light with longitudinal polarization, which has some intriguing possibilities for particle acceleration. But it is difficult to obtain longitudinal polarization.
Abstract: Light is often thought of in terms of radial polarization, but longitudinal polarization is also possible, and it has some intriguing possibilities for particle acceleration. Binary optics, combined with a high-numerical-aperture lens, is a potential route to achieving light with this unusual property.
799 citations
TL;DR: Recent advances in applying a versatile PSO engine to real-number, binary, single-objective and multiobjective optimizations for antenna designs are presented, with a randomized Newtonian mechanics model developed to describe the swarm behavior.
Abstract: The particle swarm optimization (PSO) is a recently developed evolutionary algorithm (EA) based on the swarm behavior in the nature. This paper presents recent advances in applying a versatile PSO engine to real-number, binary, single-objective and multiobjective optimizations for antenna designs, with a randomized Newtonian mechanics model developed to describe the swarm behavior. The design of aperiodic (nonuniform and thinned) antenna arrays is presented as an example for the application of the PSO engine. In particular, in order to achieve an improved peak sidelobe level (SLL), element positions in a nonuniform array are optimized by real-number PSO (RPSO). On the other hand, in a thinned array, the on/off state of each element is determined by binary PSO (BPSO). Optimizations for both nonuniform arrays and thinned arrays are also expanded to multiobjective cases. As a result, nondominated designs on the Pareto front enable one to achieve other design factors than the peak SLL. Optimized antenna arrays are compared with periodic arrays and previously presented aperiodic arrays. Selected designs fabricated and measured to validate the effectiveness of PSO in practical electromagnetic problems
760 citations
TL;DR: A new super-resolution microscope for optical imaging that beats the diffraction limit of conventional instruments and the recently demonstrated near-field optical superlens and hyperlens is reported.
Abstract: The maximum imaging resolution in classical optics is limited to approximately the wavelength of light used, and subwavelength resolution can only be achieved by advanced imaging schemes. The appeal of the super-oscillatory lens optical microscope described here is that it enables subwavelength imaging with, in principle, unlimited resolution using a modified conventional microscope. The past decade has seen an intensive effort to achieve optical imaging resolution beyond the diffraction limit. Apart from the Pendry–Veselago negative index superlens1, implementation of which in optics faces challenges of losses and as yet unattainable fabrication finesse, other super-resolution approaches necessitate the lens either to be in the near proximity of the object or manufactured on it2,3,4,5,6, or work only for a narrow class of samples, such as intensely luminescent7,8 or sparse9 objects. Here we report a new super-resolution microscope for optical imaging that beats the diffraction limit of conventional instruments and the recently demonstrated near-field optical superlens and hyperlens. This non-invasive subwavelength imaging paradigm uses a binary amplitude mask for direct focusing of laser light into a subwavelength spot in the post-evanescent field by precisely tailoring the interference of a large number of beams diffracted from a nanostructured mask. The new technology, which—in principle—has no physical limits on resolution, could be universally used for imaging at any wavelength and does not depend on the luminescence of the object, which can be tens of micrometres away from the mask. It has been implemented as a straightforward modification of a conventional microscope showing resolution better than λ/6.
587 citations
TL;DR: In this article, the authors proposed to obtain intense optical fields, whose form shows little change in size over long paths, through the use of either conical lenses or spherical lenses showing spherical aberration together with a single projecting lens.
Abstract: It is proposed to obtain intense optical fields, whose form shows little change in size over long paths, through the use of either conical lenses or spherical lenses showing spherical aberration together with a single projecting lens. The conical lens is shown to produce fields whose transverse structure is given by a zero-order Bessel function J0, while the spherical aberrating lens produces (real or virtual) J0-like transverse structures, provided that the central portion of the aberrating lens is occluded. In all cases projection gives a J0 real-image optical structure. Intensity, size of the transverse structure, and range considerations are developed, and some aspects of optimization are discussed. A negative aberrating lens gives a long range of nearly constant size in the image field, and a universal expression is presented to describe the image size as a function of image distance for this case. Projection with an aberrating projection lens is shown to improve the constancy of the final J0 pattern size dramatically. Typical photographic results are included for beams generated by using a low-power He–Ne laser. Brief considerations of practical uses of diffractionless beams are presented.
550 citations