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.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

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.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

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.

/pdf/optical-vortices-30-years-on-oam-manipulation-from-2yknluuuga.pdf

Optical vortices 30 years on: OAM manipulation from topological charge to multiple singularities

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.

Non-invasive single-shot imaging through scattering layers and around corners via speckle correlations

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.

/pdf/light-management-for-photovoltaics-using-high-index-2u8o7699oo.pdf

Light management for photovoltaics using high-index nanostructures.

12.2: An Ultra‐thin Directional Backlight Auto‐stereoscopic Display

Display illumination with modulated directional backlight

The ligand type and the number of each type of ligand can be determined with CV spectra of RE ions. This technique provides a simple method to measure the number of metal-coordinated water molecules and in this technique no D2O replacement is needed. Therefore, the range of ligands whose binding numbers can be determined directly is also extended. This spectroscopic technique is not limited by the form of sample and has high detecting sensitivity. It can be used as a structure analysis method for usual samples, and more important, it can also be used as a spectral probe of the coordination environment of RE ions in biological samples. So CV technique is especially important for studying the biological functions of RE elements.

Determination of coordination environment of rare earth ions with cooperative vibronic spectroscopy

Resonant photonic bandgap structures, formed by Bragg-spaced quantum wells, are studied experimentally with resonant pump-probe spectroscopy. We find ultrafast suppression due to the ac Stark effect and ultrafast recovery enabled by superradiant decay of the coherent polarization.

Ultrafast suppression and recovery of a resonant photonic bandgap

The invention discloses a color filtering method and device of a multicolor displayer. The method comprises the steps that the position sequences of all sub-pixels in pixel units in the multicolor displayer are acquired; the maximum relative luminance difference of all the sub-pixels in the position sequences is acquired according to color intensity distributions generated by overlapping additional film layers of the multicolor displayer in the pixel units; the position sequences of the sub-pixels in the pixel units are changed, and the position of each sub-pixel in each pixel unit is configured according to the position sequence with the minimum maximum relative luminance difference corresponding to the color intensity distributions in a display screen. According to the color filtering method and device of the multicolor displayer, the maximum relative luminance difference of the sub-pixels in the pixel units is calculated, the positions of the sub-pixels in the pixel units are set by selecting the arrangement mode of the sub-pixels under the condition of selecting the minimum maximum relative luminance difference, and therefore moire fringes can be weakened, and the display quality of the displayer can be improved.

Jianying Zhou

Papers

12.2: An Ultra‐thin Directional Backlight Auto‐stereoscopic Display

Display illumination with modulated directional backlight

Determination of coordination environment of rare earth ions with cooperative vibronic spectroscopy

Ultrafast suppression and recovery of a resonant photonic bandgap

Color filtering method and device of multicolor displayer