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.

Programmable Plenoptic Function for High-Quality Directional Backlight Autostereoscopy

Run-hua Li, Jian-xin Meng, Jian-ying Zhou," State Key Laboratory of Ultrafast Laser Spectroscopy Laboratory, Zhongshan University, Guangzhou 510275, CHINA Determining local structures surrounding metal ions in condensed phase, especially in a noncrystallized state, has been a difficult and interesting subject. In this work, we apply cooperative optical vibronic spectroscopy (COVS) to characterize the local structures surrounding rare earth ions ( R E ) . An RE interacts with its neighbor ligand through coulombic force and RE and ligand can absorb or emit photons cooperatively at the frequency of vcv = v ~ , f vile, where v,, is the frequency of an electronic transition for RE and vli( is the frequency of an infrared active transition for the ligand.' The absolute oscillator strength for COVS, P,, depends on the oscillation strength of the electronic transition for RE, P<,, and of the infrared active transition of the ligands, PI,, as well as on the mole fraction, or the number of the particular ligands in the first coordination sphere of the RE, n. That is:

Optical Characterization For Metal-ligand Structure: Cooperative Vibronic Spectroscopy

The image of an object behind turbid layers is recovered from speckles by an adaptive phase control technique assisted with Pearson correlation coefficient from a reference image, and hence image recovery fidelity is substantially improved.

Image recovery behind turbid layers by correlation with an identified object

P-88: Numerical Simulation and Quantitative Evaluation for Motional Display Uniformity in a Directional Backlight Glasses-free 3D Display

The plenoptic function [1] can be applied to describe a totality of light rays or radiance in three-dimensional (3D) space through any position and in any direction. This function describes everything that can be seen, as defined by Adelson [1] by Where ,  corresponds to the orientation or direction of a ray depending on the intensity with wavelength of  . t is the time dimension, and corresponds to a point in space [2] . We introduce the plenoptic function for backlight directional display illumination, which requires angular and position invariant smoothness on the display surfac e [3-4] . , x z P

Jianying Zhou

Papers

Programmable Plenoptic Function for High-Quality Directional Backlight Autostereoscopy

Optical Characterization For Metal-ligand Structure: Cooperative Vibronic Spectroscopy

Image recovery behind turbid layers by correlation with an identified object

P-88: Numerical Simulation and Quantitative Evaluation for Motional Display Uniformity in a Directional Backlight Glasses-free 3D Display

6.3: Harnessing Plenoptic Function with Composite Thin Films for Display