The past decade has seen an intensive effort to achieve optical imaging resolution beyond the diffraction limit. Apart from the Pendry-Veselago negative index superlens, 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 it, or work only for a narrow class of samples, such as intensely luminescent or sparse 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.

Super-oscillatory optical lenses have recently been shown to achieve subwavelength focusing and have been used for super-resolution imaging. However, the subwavelength hotspots created by these lenses are always accompanied by sidebands containing a significant fraction of the optical energy and are highly localised in the axial direction. Here, we report a class of super-oscillatory lenses that form extended subwavelength optical needles on a 15λ field of view.

Subradiant excitations, originally predicted by Dicke, have posed a long-standing challenge in physics owing to their weak radiative coupling to environment. Here we engineer massive coherently driven classical subradiance in planar metamaterial arrays as a spatially extended eigenmode comprising over 1000 metamolecules. By comparing the near-and far-field response in large-scale numerical simulations with those in experimental observations we identify strong evidence for classically correlated multimetamolecule subradiant states that dominate the total excitation energy. We show that similar spatially extended many-body subradiance can also exist in plasmonic metamaterial arrays at optical frequencies. DOI: 10.1103/PhysRevLett.119.053901 The classic example of neutrons and magnetic dipole radiation by Dicke [1] over 60 years ago describes the collective super-radiant and subradiant response of emitters at high density. Super-radiance, where the emission is enhanced due to constructive interference, has been experimentally observed in a variety of systems [2]. For subradiant states the emission is suppressed owing to the destructive interference of the radiation from the emitters. Because of the inherently weak coupling of the subradiant states to external electromagnetic (EM) fields, their experimental studies have been limited. In the early experiments subradiant emission was observed for two trapped ions [3] as well as for two trapped molecules [4]. Two-particle subradiant and super-radiant states have an analogy with the gerade (even) and ungerade (odd) symmetry states of homonuclear molecular dimers, and subradiant states have also been created in weakly bound ultracold Sr 2 [5] and Yb 2 [6] molecules. Super-radiant states in dimers represent excitations via strong electric dipole transitions, while subradiant states may, e.g., be produced by weak magnetic dipole or electric quadrupole transitions.Similar effects have been investigated in the context of plasmonics, where the analogy between nanostructured plasmonic resonators and molecular states encountered in natural media has lead to a plasmon hybridization theory [7]. Excitations in such systems, reminiscent of molecular wave functions, have consequently resulted in an analysis of dark and bright modes, with subradiant and super-radiant characteristics, respectively. Narrow Fano resonances in the transmitted field or subradiant and super-radiant excitations were experimentally observed in plasmonic resonators consisting of three or four nanorods [8,9], and in plasmonic heptamers [10][11][12], while efforts to increase the mode complexity of the resonators are attracting considerable attention [13,14]. Recent theoretical work also highlighted that the connection between transmission resonances and the existence of subradiant excitations is less obvious than commonly recognized, since narrow Fano resonances are also produced by the interference of nonorthogonal modes even in the absence of subradiance [15,16].Experiments on EM field transmission in lar...

We present the key results from a comprehensive study of the refraction and focusing properties of a two-dimensional dodecagonal photonic "quasicrystal" (PQC), carried out via both full-wave numerical simulations and microwave measurements on a slab made of alumina rods inserted in a parallel-plate waveguide. We observe anomalous refraction and focusing in several frequency regions, confirming some recently published results. However, our interpretation, based on numerical and experimental evidence, differs substantially from the one in terms of "effective negative refractiveindex" that was originally proposed. Instead, our study highlights the critical role played by shortrange interactions associated with local order and symmetry.PACS numbers: 42.70. Qs, 41.20.Jb, 61.44.Br, Since the pioneering work by Yablonovitch 1 and John 2 , "photonic crystals" (PCs) have elicited great attention from the scientific community, in view of the variety of peculiar electromagnetic (EM) bandgap, waveguiding/confinement, refraction, and emission effects attainable through their use. Among the most intriguing applications, it is worth mentioning those to negative refraction and subwavelength imaging ("superlensing") 3,4,5,6 . The most typical PC configurations are based on dielectric inclusions (or voids) arranged according to periodic lattices in a host medium, and can thus be studied using well-established tools and concepts such as Bloch theorem, unit cell, Brillouin zone, equifrequency surfaces, etc.With specific reference to lensing applications, two different approaches have been presented to obtain subwavelength resolution using a dielectric PC slab. In the first one, a PC with high dielectric contrast is tuned so as to behave (usually near a frequency band edge) like a homogeneous material with a negative refractive index n = −1 3 , and the focus position of the flat lens follows a simple ray-optical construction 7 . In the second approach, "all angle negative refraction" (AANR) is achieved without an effective negative index, provided that the equifrequency surfaces (EFSs) of the PC are all convex and larger than the one pertaining to the host medium 8 . In this case, the focus position does not follow the ray-optical construction and is restricted 9 .During the last decade, the discovery in solidstate physics of certain metallic alloys (the so-called "quasicrystals" 10,11 ) whose X-ray diffraction spectra exhibit "noncrystallographic" rotational symmetries (e.g., 5-fold or (K > 6)-fold, known to be incompatible with spatial periodicity) has generated a growing interest toward aperiodically-ordered geometries, leading to the study of the so-called "photonic quasicrystals" (PQCs). In this framework, useful tools for geometrical parameterization can be borrowed from the theory of "aperiodic tilings" 12 . Several recent numerical and experimental studies have explored the EM properties of PQCs, in the form of two-dimensional (2-D) aperiodic arrays of cylindrical rods or holes, as well as 3-D structures fabricated via stere...