2D Photonic Structures Research Articles

Translucent in air and iridescent in water: structural analysis of a salamander egg sac.

Females of some Asian salamanders of the genus Hynobius deposit in streams their eggs embedded in a translucent envelope called an 'egg sac'. The edges of the envelope exhibit a spectacular blue-to-yellow iridescent glow, which instantaneously disappears when the sac is removed from water. First, our scanning electron microscopy analyses reveal that the inner surface of the 100 μm-thick envelope displays striations (length scale of about 3 μm), which are themselves covered by much smaller (190 ± 30 nm) and quasi-periodic corrugations. The latter could constitute a surface diffraction grating generating iridescence by light interference. Second, our transmission electron microscopy and focused-ion-beam scanning electron microscopy analyses show that the bulk of the egg sac wall is composed of meandering fibres with a quasi-periodic modulation of 190 ± 60 nm along the thickness of the envelope, generating a photonic crystal. Third, Fourier power analyses of 450 electron microscopy images with varying incident angles indicate that changing the surrounding medium from water to air shifts most of the backscattered power spectrum to the ultraviolet range, hence, explaining that the egg sac loses visible iridescence when removed out of the water. Fourth, the results of our photography and optical spectroscopy experiments of submerged and emerged egg sacs rule out the possibility that the iridescence is due to a thin film or a multilayer, whereas the observed non-specular response is compatible with the backscattering expected from surface diffraction gratings and volumetric photonic crystals with spatial 1D modulation. Finally, although we mention several potential biological functions of the egg sac structural colours and iridescence, we emphasise that these optical properties might be the by-products of the envelope material internal structure selected during evolution for its mechanical properties.

One-photon absorption based direct laser writing for fabrication of multi-dimensional photonic and plasmonic nanostructures

We have successfully demonstrated a simple and low-cost fabrication technique, called direct laser writing (DLW), for realisation of photonic and plasmonic nanostructures. First, based on low one-photon absorption (LOPA) phenomena in a weakly absorbing photoresist (532 nm laser vs. SU8 or S18 photoresist), this DLW enabled production of submicrometre 2D and 3D photonic structures on demand using a very modest laser power. We also demonstrated that the LOPA based DLW allowed embedding a single nanoparticle (fluorescent, nonlinear, magnetic, or metallic nature) in a desired position of polymeric photonic structures. Second, by using optically induced local thermal effect, the DLW allowed us to directly fabricate plasmonic nanostructures on gold and/or silver films. Different applications of these fabricated photonic and plasmonic structures could be envisioned, and partially realised, such as tunable photonic devices, data storage, bright single photon source, quantum information, plasmonic data storage, and colour nanoprinter.

Повышение эффективности полимерного нанокомпозита для формирования фотонных структур методом оптической записи

In this work, the conditions for optimizing an optical recording material based on photosensitive acrylate-urethane nanocomposites with silicon oxide nanoparticles, for efficient Bragg gratings recording by multibeam interference method is presented. It was shown that the choice of the most effective monomers and their concentrations in the nanocomposite which depends on their structure and polymerization rate, followed by determination of the optimal recording radiation intensity for the given composition, makes it possible to adjust the conditions for component diffusion and redistribution, and hence, the formation of regions with different refractive indices in the recording medium. These results can be useful for creating complex 2D and 3D photonic structures based on the targeted modification of photosensitive polymer nanocomposites with different properties (luminescent, nonlinear optical, etc.).

3D electronic and photonic structures as active biological interfaces

AbstractBiocompatible materials and structures with three‐dimensional (3D) architectures establish an ideal platform for the integration of living cells and tissues, serving as desirable interfaces between biotic and abiotic systems. While conventional 3D bioscaffolds provide a mechanical support for biomatters, emerging developments of micro‐, nano‐, and mesoscale electronic and photonic devices offer new paradigms in analyzing and interrogating biosystems. In this review, we summarize recent advances in the development of 3D functional biointerfaces, with a particular focus on electrically and optically active materials, devices, and structures. We first give an overview of representative methods for manufacturing 3D biointegrated structures, such as chemical synthesis, microfabrication, mechanical assembly, and 3D printing. Subsequently, exemplary 3D nano‐, micro‐, and mesostructures based on various materials, including semiconductors, metals, and polymers are presented. Finally, we highlight the latest progress on versatile applications of such active 3D structures in the biomedical field, like cell culturing, biosignal sensing/modulation, and tissue regeneration. We believe future 3D micro‐, nano‐, and mesostructures that incorporate electrical and/or optical functionalities will not only profoundly advance the fundamental studies in biological sciences, but also create enormous opportunities for medical diagnostics and therapies.image

Optical properties of 2D photonic structures fabricated by direct laser writing

This paper presents the results of fabrication and investigation of different 2D photonic structures with the square C4v, hexagonal C6v, and pentagonal local C5v symmetry. The samples were created using the direct laser writing technique. The number of submicron scatterers varied from 25 to 10,000, and the lattice parameters varied in different samples in the range of 0.5 μm ≤ a ≤ 8.0 μm. Our experimental and theoretical studies demonstrate that 2D photonic structures reveal many remarkable optical effects. Created ordered and disordered photonic structures demonstrate a great variety of optical phenomena observed on a far-field screen placed behind the sample. When the random fluctuations of the orientation for individual rods were introduced to the perfect fishnet photonic structure, a crossover from Laue diffraction to speckle patterns was observed and investigated.

An energy window study of light transmission-disorder relationship in 1D photonic structures

While the light transmission of photonic crystals is characterized by the photonic band gap, the one of disordered photonic structures is typified by a multiplicity of transmission depths. The total transmission over a range of wavelengths is related to the width of such range, but also to the type of disorder. Less homogeneous disordered structures transmit more light than the ordered counterpart regardless of the wavelengths range width. More homogeneous disordered structures transmit more light than the ordered counterpart only above a certain value of the width. We studied this behaviour with a statistical analysis over 5000 permutations of structures for six wavelength widths and for two different homogeneity degrees (Shannon-Wiener index).

Bioinspired 2D Nanomaterials for Sustainable Applications

The increasing demand for constructing ecological civilization and promoting socially sustainable development has encouraged scientists to develop bioinspired materials with required properties and functions. By bringing science and nature together, plenty of novel materials with extraordinary properties can be created by learning the best from natural species. In combination with the exceptional features of 2D nanomaterials, bioinspired 2D nanomaterials and technologies have delivered significant achievements. Here, the progress over the past decade in bioinspired 2D photonic structures, energy nanomaterials, and superwetting materials, is summarized, together with the challenges and opportunities in developing bioinspired materials for sustainable energy and environmental technologies.

The realization of the intermediate layer (IML) in a tandem solar cell using silicon-based photonic ribbon structure

The silicon-based 1D photonic structure is proposed in this research to realize an intermediate layer, which could be used in tandem solar cell, where 1 D photonic structure deals with a silicon ribbon with having 10 number of circular periodic air hole on it. Further, the principle of realization of the present intermediate layer is based on the generation of photonic band gap with respect to the visible light, which is evaluated with the help of the plane wave expansion method. Finally, photonic band gap analysis confirms that the proposed one-dimensional photonic ribbon structure can be a suitable layer to introduce in a tandem solar cell to envisage better efficiency.

SiOx by magnetron sputtered revisited: Tailoring the photonic properties of multilayers

Abstract Traditionally porous silicon based photonic structures have been prepared by electrochemically etching of silicon. In this work, porous multilayers of nanocolumnar SiOx and SiO2 thin films acting as near infrared (NIR) 1D-photonic nanostructures are prepared by magnetron sputtering deposition at oblique angles (MS-OA). Simultaneous control of porosity and stoichiometry of the stacked films is achieved by adjusting the deposition angle and oxygen partial pressure according to a parametric formula. This new methodologoy is proved for the synthesis of SiOx thin films with x close to 0.4, 0.8, 1.2, 1.6 and nanostructures varying from compact (at 0° deposition angle) to highly porous and nanocolumnar (at 70° and 85° deposition angles). The strict control of composition, structure and nanostructure provided by this technique permits a fine tuning of the absorption edge and refraction index at 1500 nm of the porous films and their manufacturing in the form of SiOx-SiO2 porous multilayers acting as near infrared (NIR) 1D-photonic structures with well-defined optofluidic responses. Liquid tunable NIR Bragg mirrors and Bragg microcavities for liquid sensing applications are presented as proof of concept of the possibilities of this MS-OA manufacturing method as an alternative to the conventional electrochemical fabrication of silicon based photonic structures.

Beyond Seashells: Bioinspired 2D Photonic and Photoelectronic Devices

AbstractThe discovery of novel materials that possess extraordinary optical properties are of special interest, as they inspire systems for next‐generation solar energy harvesting and conversion devices. Learning from nature has inspired the development of many photonic nanomaterials with fascinating structural colors. 2D photonic nanostructures, inspired by the attractive optical properties found on the inner surfaces of seashells, are fabricated in a facile and scalable way. The shells generate shining clusters for preying on phototactic creatures through interaction with incident solar light in water. By alternately depositing graphene and 2D ultrathin TiO2 nanosheets to form 2D–2D heterostructures and homostructures, seashell‐inspired nanomaterials with well‐controlled parameters are successfully achieved. They exhibit exceptional interlayer charge transfer properties and ultrafast in‐plane electron mobility and present fascinating nacre‐mimicking optical properties and significantly enhanced light‐response behavior when acting as photoelectrodes. A window into the fabrication of novel 2D photonic structures and devices is opened, paving the way for the design of high‐performance solar‐energy harvesting and conversion devices.

Distortion analysis of crystalline and locally quasicrystalline 2D photonic structures with grazing-incidence small-angle X-ray scattering

In this study, grazing-incidence small-angle X-ray scattering (GISAXS) is used to collect statistical information on dimensional parameters in an area of 20 × 15 mm on photonic structures produced by nanoimprint lithography. The photonic structures are composed of crystalline and locally quasicrystalline two-dimensional patterns with structure sizes between about 100 nm and 10 µm to enable broadband visible light absorption for use in solar-energy harvesting. These first GISAXS measurements on locally quasicrystalline samples demonstrate that GISAXS is capable of showing the locally quasicrystalline nature of the samples while at the same time revealing the long-range periodicity introduced by the lattice design. The scattering is described qualitatively in the framework of the distorted-wave Born approximation using a hierarchical model mirroring the sample design, which consists of a rectangular and locally quasicrystalline supercell that is repeated periodically to fill the whole surface. The nanoimprinted samples are compared with a sample manufactured using electron-beam lithography and the distortions of the periodic and locally quasiperiodic samples are quantified statistically. Owing to the high sensitivity of GISAXS to deviations from the perfect lattice, the misalignment of the crystallographic axes was measured with a resolution of 0.015°, showing distortions of up to ±0.15° in the investigated samples.

A proposal to identify live cancer cell by naked eye: Realization of biomedical application using 1D photonic structure

The present communication deals with the investigation of the type of cell either normal or cancerous using one dimensional photonic structure, where the proposed structure manipulates with three layers of silicon (1 st and 3rd layer) and examining cell (2nd layer). Furthermore, the principle of detection of cell is based on the analysis of the reflected signal as well as the photonic band gap of the said structure. Lastly, the outcomes of quantitative analysis confirm that the naked eye could detect the type of cell. For example, if the reflected signal belongs to red color zone then cell would be normal. Similarly, the cell could be cancerous, if the reflected signal belongs to black color zone.

Estimation of concentration of DNA and protein through PARD and modified analysis: A realization of an accurate biomedical device using photonic structure

The concentration of DNA and protein is estimated in this paper using a 2D photonic structure with the inclusion of propagation, absorption, reflection, and diffraction (PARD) losses along with the modified equation at the signal of 400 nm. Simulation studies with the help of the plane wave expansion method disclosed to compute the reflection characteristics, where other sorts of losses such as propagation, absorption, and diffraction are divulged by means of numerical computation. Final output in terms of transmitted power is an excellently fitted with linear trend line with respect to the concentration of DNA which varies from 0 to 0.025 gm/mL and protein from 0 to 0.01 gm/mL, which leads to an accurate investigation of aforementioned of biomaterials.

Realization of a three-dimensional photonic topological insulator.

Confining photons in a finite volume is highly desirable in modern photonic devices, such as waveguides, lasers and cavities. Decades ago, this motivated the study and application of photonic crystals, which have a photonic bandgap thatforbids light propagation in all directions1-3. Recently, inspired by the discoveries of topological insulators4,5, the confinement of photons with topological protection has been demonstrated in two-dimensional (2D) photonic structures known as photonic topological insulators6-8, with promising applications in topological lasers9,10 and robust optical delay lines11. However, a fully three-dimensional (3D) topological photonic bandgap has not been achieved. Here we experimentally demonstrate a 3D photonic topological insulator with an extremely wide (more than 25 per cent bandwidth) 3D topological bandgap. The composite material (metallic patterns on printed circuit boards) consists of split-ring resonators (classical electromagnetic artificial atoms) with strong magneto-electric coupling and behaves like a 'weak' topological insulator (that is, with an even number of surface Dirac cones), or a stack of 2D quantum spin Hall insulators. Using direct field measurements, we map out both the gapped bulk band structure and the Dirac-like dispersion of the photonic surface states, and demonstrate robust photonic propagation along a non-planar surface. Our work extends the family of 3D topological insulators from fermions to bosons and paves the way for applications in topological photonic cavities, circuits and lasers in 3D geometries.

Nanocoatings on 2D Macroporous Silicon Structures

Macroporous silicon formed by photoanodic etching with high aspect ratio and large effective surface is one of the promising materials for the development of 2D photonic structures. We fabricated nanocoatings of CdTe, ZnO, CdS surface nanocrystals and SiO2 layers on macroporous silicon surface. The near-IR optical absorption was investigated and well-separated oscillations with giant amplitude were observed in the spectral ranges of surface level absorption. This process is because of resonance electron scattering on the surface impurity states with the difference between two resonance energies equal to the Wannier-Stark ladder. Macroporous silicon structures with SiO2 nanolayers and CdS nanocrystals are proposed to enhance the photoluminescence of CdS nanoparticles with quantum yield 28%. Addition functionalization of 2D macroporous silicon is a result of the high-pressure oxidation. The structural SiO2 reorganization to orthorhombic phase increases the concentration of paramagnetic Pb centers, EPR signal amplitude and GHz radiation absorption.

Bio‐Inspired Plasmonic Photocatalysts

AbstractThe conversion of solar energy to sustainable energy sources is a significant field of study for the relief of the world's energy problems, and among the various strategies developed, semiconductor photocatalysts have received significant attention as a promising candidate due to their attractive efficiency, mild reaction conditions, and low cost. The enhancement of such photocatalysts with plasmonic materials, by virtue of the Schottky junction and localized surface plasma resonance phenomenon, could facilitate the rapid progress in enhancement of photocatalytic efficiency under visible light irradiation. To further improve photocatalytic efficiency, scientists look to nature for inspiration, culminating in the evolution of complex hierarchical structures in order to fully utilize the potential of solar energy. In the past decade, there has been significant progress in the development of bio‐inspired plasmonic photocatalysts, such as antireflective surfaces, 3D photonic structures, and branched structures. This review describes the state‐of‐the‐art bio‐inspired light manipulation approaches, as well as future challenges in solar energy harvesting by plasmonic photocatalysts.

The external quantum efficiency of multijunction solar cells with built-in 1D photonic crystals

In the present research, a multijunction solar cell with a built-in 1D photonic structure − Bragg reflector − is investigated. The joint effect of photon recycling and luminescence coupling on the spectral characteristics of the external quantum efficiency of multijunction solar cells is considered.

Photonic Crystals: Topology-Optimized 3D Photonic Structures with Maximal Omnidirectional Bandgaps (Adv. Theory Simul. 12/2018)

3D photonic crystals are critical for diverse engineering applications, but there are widespread challenges in intuitively designing their complex structures. In article number 1800122, Xiaodong Huang and co-workers utilize computer modelling and intelligent topology optimization, to systematically create 3D photonic structures with on-demand broad omnidirectional bandgaps. The findings expand the existing knowledge on the geometrical characteristics of photonic bandgap crystals.

Fabrication of Photonic Bandgap Materials by Shifting Double Frameworks.

Biological organisms have evolved over millions of years to generate tremendously complex structures on a nanometer to micrometer scale. Among them, a range of three-dimensional (3D) biological photonic structures with minimal surface or constant mean curvature surfaces have been discovered in the wing scales of insects, attracting a great deal of interest because of their unique optical properties, such as structural color, antireflection, light collection, and photonic band gaps. Single-diamond and single-gyroid surface structures are considered to be excellent photonic crystals with complete band gaps. Although the corresponding bicontinuous architectures have been synthesized by self-assembly, single-framework structures are thermodynamically unfavorable and have been only achieved by physical fabrications and the alternating gyroid method. The production of materials derived from the thermodynamically stable double-framework structures provides a feasible solution for their chemical construction. This concept article highlights the significant progress in understanding 3D photonic structures by shifting double-frameworks to form low-symmetry structures, the physical properties of which can be greatly altered. Specifically, a complete photonic band gap can be achieved via a shifted double-diamond structure composed of materials with high dielectric contrast and high refractive index. We believe this concept will provide new insights in interdisciplinary research areas including the study of photonic structures, the self-assembly of amphiphilic molecules and the formation of biological architectures.

Topology‐Optimized 3D Photonic Structures with Maximal Omnidirectional Bandgaps

Three-dimensional photonic crystals with large omnidirectional bandgaps are critical for diverse device applications, but have been challenging to design due to their structural complexity. A topology optimization algorithm based on the evolutionary topology optimization method to design omnidirectional bandgaps on demand is proposed. Considering an asymmetric simple cubic lattice, large bandgaps between any two neighbor bands are successfully realized and novel 3D photonic structures obtained. The topology-optimized designs have a uniform bicontinuous character, which originates from the orthogonal distribution of electric fields at the bounds of the bandgaps. The distribution of the dielectric material follows the directions of the wave vectors of the maximum frequencies at the lower bounds. Consequently, the macroscopic effective properties, such as permittivity, exhibit corresponding directionality. The isotropy of effective permittivity indicates the flatness of the lower bound and photonic crystals with large bandgaps tend to have isotropic effective permittivity.