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Author

Jianying Zhou

Other affiliations: Max Planck Society
Bio: Jianying Zhou is an academic researcher from Sun Yat-sen University. The author has contributed to research in topics: Backlight & Ultrashort pulse. The author has an hindex of 28, co-authored 173 publications receiving 3162 citations. Previous affiliations of Jianying Zhou include Max Planck Society.


Papers
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Journal ArticleDOI
TL;DR: A novel approach for designing richer Fourier spectra is introduced, by using a periodic structure that allows us to control its Fourier components almost at will, and it is shown how these structures can be employed to achieve highly efficient broad-band light trapping in thin films that approach the theoretical limit.
Abstract: Controlling the flux of photons is crucial in many areas of science and technology. Artificial materials with nano-scale modulation of the refractive index, such as photonic crystals, are able to exercise such control and have opened exciting new possibilities for light manipulation. An interesting alternative to such periodic structures is the class of materials known as quasi-crystals, which offer unique advantages such as richer Fourier spectra. Here we introduce a novel approach for designing such richer Fourier spectra, by using a periodic structure that allows us to control its Fourier components almost at will. Our approach is based on binary gratings, which makes the structures easy to replicate and to tailor towards specific applications. As an example, we show how these structures can be employed to achieve highly efficient broad-band light trapping in thin films that approach the theoretical (Lambertian) limit, a problem of crucial importance for photovoltaics.

236 citations

Journal ArticleDOI
TL;DR: In this article, a planar bidentate ligand and two twisted bipy ligands with torsional angles between each bipyridine were used to construct the complex.
Abstract: Imidazo[4,5-f]1,10-phenanthroline (ip), 2-phenylimidazo[4,5-f][1,10]phenanthroline (pip) and their (bipy) 2 Ru 2+ complexes (bipy = 2,2′-bipyridine) have been synthesized and characterized The oxidation potentials of [Ru(bipy) 2 (ip)] 2+ and [Ru(bipy) 2 (pip)] 2+ were found to be 1254 and 1284 V vs saturated calomel electrode respectively; the reduction of ip and pip appears to be irreversible at ca -085 V The photophysical properties of the complexes were perturbed in the presence of calf thymus DNA The distinct changes including hypo- or hyper-chromicity at different UV/VIS absorption bands, enhancements of integrated emission intensity and excited-state lifetime, and efficiency of emission quenching by [Fe(CN) 6 ] 4- all indicate the stronger binding affinity to DNA of [Ru(bipy) 2 (pip)] 2+ over that of [Ru(bipy) 2 (ip)] 2+ , consistent with the greater planar area and extended π system of the pip ligand The luminescence of the complexes showed monoexponential decay at any [DNA]∶[Ru] ratio The circular dichroism signals of the dialysates of the racemic complexes against calf thymus DNA suggest that the complexes bind to the DNA with enantioselectivity favouring the Δ isomers These phenomena all suggest that the complexes bind through intercalation of ip or pip into base pairs The crystal structure of [Ru(bipy) 2 (ip)][ClO 4 ] 2 ·H 2 O was determined; it contains the planar bidentate ligand ip and two twisted bipy ligands with torsional angles between each bipyridine ring pair of 57 and 86°

197 citations

Journal ArticleDOI
TL;DR: In this article, the binding properties of the two complexes to calf thymus DNA has been investigated with spectrophotometric methods and viscosity measurements, and the experimental results indicate that the complexes bind to DNA through a partial intercalative mode that is different from the bonding mode for their parent compound, [Ru(bpy)2(PIP)]2+ (PIP=2-phenylimidazo[4,5-f]1,10-phenanthroline).
Abstract: 2-(2-Chlorophenyl)imidazo[4,5-f]1,10-phenanthroline (CIP) or 2-(2-nitrophenyl)imidazo[4,5-f]1,10-phenanthroline (NIP) and their complexes [Ru(bpy)2(CIP)]2+ and [Ru(bpy)2(NIP)]2+ (bpy = 2,2′-bipyridine) have been synthesized and characterized. The binding of the two complexes to calf thymus DNA has been investigated with spectrophotometric methods and viscosity measurements. The experimental results indicate that the two complexes bind to DNA through a partial intercalative mode that is different from the bonding mode for their parent compound, [Ru(bpy)2(PIP)]2+ (PIP = 2-phenylimidazo[4,5-f]1,10-phenanthroline). The crystal structure of [Ru(bpy)2(CIP)][ClO4]2·2H2O was determined by X-ray diffraction analysis; the imidazo[4,5-f]1,10-phenanthroline moiety is not coplanar with the 2-chlorophenyl ring, having a dihedral angle of 44.5° in the CIP.

171 citations

Journal ArticleDOI
TL;DR: This work introduces and demonstrates a metalens with a high NA and high transmission in the visible range, based on crystalline silicon (c-Si), and envision the front-immersion design to be beneficial for achieving ultrahigh-NA metalenses as well as immersion metalens doublets, thereby pushing metasurfaces into practical applications such as high resolution, low-cost confocal microscopy and achromatic lenses.
Abstract: Subwavelength imaging requires the use of high numerical aperture (NA) lenses together with immersion liquids in order to achieve the highest possible resolution. Following exciting recent developments in metasurfaces that have achieved efficient focusing and novel beam-shaping, the race is on to demonstrate ultrahigh-NA metalenses. The highest NA that has been demonstrated so far is NA = 1.1, achieved with a TiO2 metalens and back-immersion. Here, we introduce and demonstrate a metalens with a high NA and high transmission in the visible range, based on crystalline silicon (c-Si). The higher refractive index of silicon compared to TiO2 allows us to push the NA further. The design uses the geometric phase approach also known as the Pancharatnam–Berry (P–B) phase, and we determine the arrangement of nanobricks using a hybrid optimization algorithm (HOA). We demonstrate a metalens with NA = 0.98 in air, a bandwidth (full width at half-maximum, fwhm) of 274 nm, and a focusing efficiency of 67% at 532 nm wave...

164 citations

Journal ArticleDOI
TL;DR: A highly symmetric excitation optical field and optimized detection scheme are proposed to harness the total point-spread function for a microscopic system, showing that the proposed scheme provides a better image quality.
Abstract: The resolution limit of far-field optical microscopy is reexamined with a full vectorial theoretical analysis. A highly symmetric excitation optical field and optimized detection scheme are proposed to harness the total point-spread function for a microscopic system. Spatial resolution of better than $1/6\ensuremath{\lambda}$ is shown to be obtainable, giving rise to a resolution better than 100 nm with visible light excitation. The experimental measurement is applied to examine nonfluorescent samples. A lateral resolution of $1/5\ensuremath{\lambda}$ is obtained in truly far-field optical microscopy with a working distance greater than $\ensuremath{\sim}500\ensuremath{\lambda}$. Comparison is made for the far-field microscopic measurement with that of a nearfield scanning optical microscopy, showing that the proposed scheme provides a better image quality.

117 citations


Cited by
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Proceedings Article
01 Jan 1999
TL;DR: In this paper, the authors describe photonic crystals as the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures, and the interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.
Abstract: The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

2,722 citations

Journal Article
TL;DR: In this article, a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators were developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of 3D micro-optical and micromechanical structures, including photonic-bandgap-type structures.
Abstract: Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.

1,833 citations

Journal ArticleDOI
TL;DR: The authors survey the steady refinement of techniques used to create optical vortices, and explore their applications, which include sophisticated optical computing processes, novel microscopy and imaging techniques, the creation of ‘optical tweezers’ to trap particles of matter, and optical machining using light to pattern structures on the nanoscale.
Abstract: Thirty years ago, Coullet et al. proposed that a special optical field exists in laser cavities bearing some analogy with the superfluid vortex. Since then, optical vortices have been widely studied, inspired by the hydrodynamics sharing similar mathematics. Akin to a fluid vortex with a central flow singularity, an optical vortex beam has a phase singularity with a certain topological charge, giving rise to a hollow intensity distribution. Such a beam with helical phase fronts and orbital angular momentum reveals a subtle connection between macroscopic physical optics and microscopic quantum optics. These amazing properties provide a new understanding of a wide range of optical and physical phenomena, including twisting photons, spin-orbital interactions, Bose-Einstein condensates, etc., while the associated technologies for manipulating optical vortices have become increasingly tunable and flexible. Hitherto, owing to these salient properties and optical manipulation technologies, tunable vortex beams have engendered tremendous advanced applications such as optical tweezers, high-order quantum entanglement, and nonlinear optics. This article reviews the recent progress in tunable vortex technologies along with their advanced applications.

1,016 citations

Journal ArticleDOI
TL;DR: In this article, a single high-resolution image of the scattered light, captured with a standard camera, encodes sufficient information to image through visually opaque layers and around corners with diffraction-limited resolution.
Abstract: Optical imaging through and inside complex samples is a difficult challenge with important applications in many fields. The fundamental problem is that inhomogeneous samples such as biological tissue randomly scatter and diffuse light, preventing the formation of diffraction-limited images. Despite many recent advances, no current method can perform non-invasive imaging in real-time using diffused light. Here, we show that, owing to the ‘memory-effect’ for speckle correlations, a single high-resolution image of the scattered light, captured with a standard camera, encodes sufficient information to image through visually opaque layers and around corners with diffraction-limited resolution. We experimentally demonstrate single-shot imaging through scattering media and around corners using spatially incoherent light and various samples, from white paint to dynamic biological samples. Our single-shot lensless technique is simple, does not require wavefront-shaping nor time-gated or interferometric detection, and is realized here using a camera-phone. It has the potential to enable imaging in currently inaccessible scenarios. Diffraction-limited imaging in a variety of complex media is realized based on analysis of speckle correlations in light captured using a camera phone.

899 citations

Journal ArticleDOI
TL;DR: This Review discusses some of the recent developments in the design and implementation of such photonic elements in thin-film photovoltaic cells, including nanoscale wires, particles and voids.
Abstract: High-performance photovoltaic cells use semiconductors to convert sunlight into clean electrical power, and transparent dielectrics or conductive oxides as antireflection coatings. A common feature of these materials is their high refractive index. Whereas high-index materials in a planar form tend to produce a strong, undesired reflection of sunlight, high-index nanostructures afford new ways to manipulate light at a subwavelength scale. For example, nanoscale wires, particles and voids support strong optical resonances that can enhance and effectively control light absorption and scattering processes. As such, they provide ideal building blocks for novel, broadband antireflection coatings, light-trapping layers and super-absorbing films. This Review discusses some of the recent developments in the design and implementation of such photonic elements in thin-film photovoltaic cells.

835 citations