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

50 Years of Image Analysis

A mean-field phase diagram for conformationally symmetric diblock melts using the standard Gaussian polymer model is presented. Our calculation, which traverses the weak- to strong-segregation regimes, is free of traditional approximations. Regions of stability are determined for disordered (DIS) melts and for ordered structures including lamellae (L), hexagonally packed cylinders (H), body-centered cubic spheres (QIm3m), close-packed spheres (CPS), and the bicontinuous cubic network with Ia3d symmetry (QIa3d). The CPS phase exists in narrow regions along the order−disorder transition for χN ≥ 17.67. Results suggest that the QIa3d phase is not stable above χN ∼ 60. Along the L/QIa3d phase boundaries, a hexagonally perforated lamellar (HPL) phase is found to be nearly stable. Our results for the bicontinuous Pn3m cubic (QPn3m) phase, known as the OBDD, indicate that it is an unstable structure in diblock melts. Earlier approximation schemes used to examine mean-field behavior are reviewed, and compa...

Unifying Weak- and Strong-Segregation Block Copolymer Theories

Perovskite solar cells (PSCs) have attracted much attention because of their rapid rise to 22% efficiencies. Here, we review the rapid evolution of PSCs as they enter a new phase that could revolutionize the photovoltaic industry. In particular, we describe the properties that make perovskites so remarkable, and the current understanding of the PSC device physics, including the operation of state-of-the-art solar cells with efficiencies above 20%. The extraordinary progress of long-term stability is discussed and we provide an outlook on what the future of PSCs might soon bring the photovoltaic community. Some challenges remain in terms of reducing non-radiative recombination and increasing conductivity of the different device layers, and these will be discussed in depth in this review.

The rapid evolution of highly efficient perovskite solar cells

A Review of Perovskites Solar Cell Stability

Jamin–Lebedeff polarizing interference microscopy is a classical method for determining the refractive index and thickness of transparent tissues. Here, we extend the application of this method to pigmented, absorbing biological tissues, based on a theoretical derivation using Jones calculus. This novel method is applied to the wings of the American Rubyspot damselfly, Hetaerina americana. The membranes in the red-colored parts of the damselfly’s wings, with a thickness of 2.5 mm, contain a pigment with maximal absorption at 490 nm and a peak absorbance coefficient of 0.7 mm 21 . The high pigment density causes a considerable and anomalous dispersion of the refractive index. This result can be quantitatively understood from the pigment absorbance spectrum by applying the Kramers–Kronig dispersion relations. Measurements of the spectral dependence of the refractive index and the absorption are valuable for gaining quantitative insight into how the material properties of animal tissues influence coloration. Light: Science & Applications (2013) 2, e100; doi:10.1038/lsa.2013.56; published online 27 September 2013

Quantifyingtherefractiveindexdispersionofapigmented biological tissue using Jamin-Lebedeff interference microscopy

The reflection of light from distributed microplatelets is an effective approach to creating color and controlling the optical properties in paints, security features, and optical filters. However, predictive tools for the design and manufacturing of such composite materials are limited due to the complex light–matter interactions that determine their optical response. Here, the optical reflectance of individual reflective microplatelets and of polymer‐based composites containing these engineered platelets as an aligned, dispersed phase are experimentally studied and analytically calculated. Transfer‐matrix calculations are used to interpret the effect of the platelet architecture, the number of platelets, and their size distribution on the experimentally measured reflectance of composites prepared using a previously established magnetic alignment technique. It is demonstrated that the reflectance of the composites can be understood as the averaged response of an array of Fabry–Pérot resonators, in which the microplatelets act as semi‐transparent flat reflectors and the polymer as cavity medium. By using an analytical model and computer simulations to describe the interaction of light with platelets embedded in a polymer matrix, this work provides useful tools for the design and fabrication of composites with tailored optical reflectance.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/adom.202201989

Optical Reflectance of Composites with Aligned Engineered Microplatelets

More than three quarters of all animal species on Earth are insects, successfully inhabiting most ecosystems on the planet. Due to their opulence, insects provide the backbone of many biological processes, but also inflict adverse impacts on agricultural and stored products, buildings and human health. To countermeasure insect pests, the interactions of these animals with their surroundings have to be fully understood. This review focuses on the various forms of insect attachment, natural surfaces that have evolved to counter insect adhesion, and particularly features recently developed synthetic bio-inspired solutions. These bio-inspired solutions often enhance the variety of applicable mechanisms observed in nature and open paths for improved technological solutions that are needed in a changing global society.

Bio-inspired materials to control and minimise insect attachment

Fruit Coloration: Attractive, Fatty Blue Colours?

Optical metamaterials offer the possibility of accessing extraordinary optical properties through the specific arrangement of their sub-wavelength structural units. A particularly interesting morphology is the gyroid due to its chiral, cubic, and triply-periodic geometry. Gyroid optical metamaterials with unit cell sizes of tens of nanometers can be conveniently fabricated via electrodeposition of gold into voided, self-assembled polymer templates. This bottom-up self-assembly approach allows the fabrication of gold gyroids with different orientations and unit cell sizes. We show here that gyroid metamaterials exhibit a depressed effective plasma frequency, as well as a circular and linear dichroism, a surprising result given the underlying cubic symmetry. By combining electron microscopy and optical goniometry, we show that the reflection of light from gold gyroids is strongly polarization-dependent, and is sensitive to the orientation of the gyroid and the terminations of its top surface. Our results highlight the influence of orientation and surface terminations on the optical properties of metamaterials, and have significant consequences for both their design and applications.

Bodo D. Wilts

Papers

Quantifyingtherefractiveindexdispersionofapigmented biological tissue using Jamin-Lebedeff interference microscopy

Optical Reflectance of Composites with Aligned Engineered Microplatelets

Bio-inspired materials to control and minimise insect attachment

Fruit Coloration: Attractive, Fatty Blue Colours?

Linear and Circular Dichroism in Gyroid Optical Metamaterials