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We have investigated the interaction between a random two-dimensional array of Ag islands near a Ag reflector, with the aim of producing a plasmonic back reflector structure with high diffuse reflectivity in the near-infrared, 600–1100 nm wavelength, region. We have demonstrated the ability to tune the power scattered and absorbed by varying the distance between the plasmonic layer and the reflector. Finite-difference-time-domain (FDTD) simulations demonstrate the tunability of the scattered and absorbed power with separation distance for a single Ag nanosphere near a planar Ag reflector. The tunability of the optical properties can be attributed to the modulation in the electric field driving the plasmonic resonance with separation distance. The simulation results indicate an intermediate distance where the scattered power peaks with minimal absorption losses. Random arrays of metal-islands were fabricated on varying thicknesses of a ZnO separation layer on a Ag reflector. Compared to a conventional textured Ag reflector, which has ∼2% diffuse reflectance in the near-infrared spectral region, the fabricated plasmonic reflector with ∼200 nm sized Ag metal islands at 100 nm separation distance from the Ag reflector shows a relatively higher, ∼24%, integrated diffuse reflectance in the near bandgap, 600–1100 nm wavelength, region for thin film silicon solar cells.

Luminescence imaging is a widely used characterization technique for silicon photovoltaics. However, the tools used to acquire images typically utilize a silicon CCD array for detection, which is a poor absorber at silicon luminescence wavelengths. This leads to a smearing effect in the measured image which can be characterized by a point spread function (PSF). If the true PSF is known then the measured image can be restored through deconvolution. Several methods exist for determining a PSF for a particular imaging system and different extraction techniques can lead to variations in the PSF result, yet no studies have provided comprehensive analysis of PSF deconvolution accuracy when applied to luminescence imaging. In this work, several new techniques have been designed and investigated in order to test PSF deconvolution results, with a view to quantifying improvement or errors generated and potentially leading towards improved image restoration.

In this report, helium ion microscopy (HIM) is used to study the micro and nano-structures responsible for structural color in the wings of two species of Lepidotera from the Papilionidae family: Papilio ulysses (Blue Mountain Butterfly) and Parides sesostris (Emerald-patched Cattleheart). Electronic charging under the beam of uncoated scales from the wings of these butterflies is successfully neutralized, leading to images displaying a large depth-of-field and a high level of surface detail, which would normally be obscured by traditional coating methods used for scanning electron microscopy (SEM). The images are compared to those from variable pressure SEM, demonstrating the superiority of HIM at high magnifications. In addition, the large depth-of-field capabilities of HIM are exploited through the creation of stereo pairs which allows the exploration of the third dimension. Furthermore, the extraction of quantitative height information which matches well with cross-sectional transmission electron microscopy (TEM) measurements from the literature is demonstrated.

We have studied the optical transmission properties of a number of different dielectric diffraction gratings that each exhibit two-dimensional chirality in their grating elements. We have found that the diffracted beams transmitted through these structures exhibit large anisotropic polarization changes and polarization-dependent intensity modulations even though the chiral elements are arranged in square grating arrays. The strength and functional form of both of these effects differ for each diffracted beam. They are also dependent on the chirality of the surface patterning and the thickness of the patterned dielectric film. We show how these properties could be exploited to provide a new and more versatile form of polarimeter, and how the operation of such a device is inherently dependent on the optical non-reciprocity of these chiral gratings.

We present an approach for the optimization of thin film antireflective coatings for encapsulated planar silicon solar cells in which the variations in the incident spectra and angle of incidence (AOI) over a typical day are fully considered. Both the angular and wavelength dependences of the reflectance from the surface, absorptance within the coating, and transmittance into the device are calculated for both single- and doublelayer antireflection coatings with and without thin silicon oxide passivation layers. These data are then combined with spectral data as a function of time of day and internal quantum efficiency to estimate the average short-circuit current produced by a fixed solar cell during a day. This is then used as a figure of merit for the optimization of antireflective layer thicknesses for modules placed horizontally at the equator and on a roof in the UK. Our results indicate that only modest gains in average short-circuit current could be obtained by optimizing structures for sunrise to sunset irradiance rather than AM15 at normal incidence, and fabrication tolerances and uniformities are likely to be more significant. However, we believe that this overall approach to optimization will be of increasing significance for new, potentially asymmetric, antireflection schemes such as those based on subwavelength texturing or other photonic or plasmonic technologies currently under development especially when considered in combination with modules fixed at locations and directions that result in asymmetric spectral conditions.

The characterization of scattered light is complex and relatively nonstandardized despite being of great importance to many optical technologies. While total scatter can be efficiently measured using integrating-sphere-based techniques, a detailed determination of the full bidirectional scattering distribution function is far more challenging, often requiring complicated and expensive equipment as well as substantial measurement time. Due to this, many research groups rely on simpler, angle-resolved scattering (ARS) measurements, yet these are typically carried out using a single wavelength source, therefore providing limited information. Here, we demonstrate a custom-built broadband angle-resolved optical spectrometer, which utilizes a supercontinuum white light laser source combined with a custom automated goniometer and a Si CCD array spectrometer in order to carry out broad spectral measurements of ARS. The use of a collimated supercontinuum allows for small area measurements that are often crucial for investigation of nanophotonic samples created using expensive fabrication techniques. The system has been tested and calibrated, and accuracy and reproducibility have been verified by integrating wavelength and ARS data over the angular range and comparing to calibrated integrating sphere measurements.

Helium ion beam lithography (HIBL) is an emerging technique that uses a sub-nanometre focused beam of helium ions generated in the helium ion microscope to expose resist. It benefits from high resolution, high sensitivity and a low proximity effect. Here we present an investigation into HIBL on a novel, negative tone fullerene-derivative molecular resist. Analysis of large area exposures reveals a sensitivity of ~40µC/cm2 with a 30keV helium beam which is almost three orders of magnitude higher than the sensitivity of this resist to a 30keV electron beam. Sparse line features with line widths of 7.3nm are achieved on the ~10nm thick resist. The fabrication of 8.5 half-pitched lines with good feature separation and 6nm half-pitched lines with inferior but still resolvable separation is also shown in this study. Thus, sub-10nm patterning with small proximity effect is demonstrated using HIBL using standard processing conditions, establishing its potential as an alternative to EBL for rapid prototyping of beyond CMOS devices. Display Omitted A novel, negative tone fullerene molecular resist was patterned using helium ion beam lithography (HIBL).Almost 3 orders of magnitude sensitivity improvement was achieved in HIBL compared to EBL for this resist.Dense single-pixel, clearly seperated line features with a half pitch down to 8.5nm were fabricated.Sub-10nm patterning was achieved with high resolution, high sensitivity and low proximity effect.

For the first time, all-dielectric planar chiral metamaterials consisting of arrays of silicon nitride gammadions on fused silica substrates have been fabricated, and shown to be capable of inducing large changes to the polarization states of transmitted light in a manner that is dependent on the two-dimensional chirality of the microstructured silicon nitride film. The polarization response is found to reverse for opposite enantiomers, and also for the same enantiomer when it is illuminated from opposite sides of the structure. In addition, the polarization states of the various diffracted beams are found to be non-reversible. These structures therefore appear to display elements of non-reciprocal behaviour. The polarization responses of complementary designs, different chiral geometries and various silicon nitride film thicknesses have also been studied. As a result we conclude that multiple reflections within the patterned silicon nitride layer play an important role in defining the mechanism by which these structures are able to modify the polarization states of diffracted light.

We have fabricated curved optical micromirrors on silicon. We expect to be able to form open optical cavities between these mirrors and plane mirrors coated on the ends of optical fibres. The curved mirror templates have been prepared with less than 10 nm surface roughness by means of isotropic chemical etching. Two different methods are used for the fabrication of the mirrors: the first method uses a silicon oxide mask, while the second uses dry etching to form an indentation in the silicon surface that is opened out by wet isotropic etching. After coating the silicon substrate with gold, good quality mirrors are obtained with R ~ 98% in the near infra-red. We find that a reflectivity of approximately 98% can be achieved by this method. Cavities formed from these mirrors will be useful for manipulating single atoms.

We have, for the first time, identified ten tenets of two-dimensional (2D) chirality that define and encapsulate the symmetry and scaling behaviour of planar objects and have used them to develop three new measures of geometric 2D chirality. All three models are based on the principle of overlap integrals and can be expressed as simple analytical functions of the two-dimensional surface density, ρ(r). In this paper we will compare the predicted behaviour of these models and show that two of them are fully integrable and scalable and can therefore be applied to both discrete and continuous 2D systems of any finite size, or any degree of complexity. The only significant difference in these two models appears in their behaviour at infinite length scales. Such differences could, however, have profound implications for the analysis of chirality in new generations of planar meta-materials, such as chiral arrays, fractals, quasi-periodic 2D crystals and Penrose tiled structures.

ZnO quantum disks are found to form on the top surface of a thick ZnO epilayer as a result of a morphology transition occurring during the growth of ZnO single-crystal thin films on c-plane sapphire using plasma-assisted molecular beam epitaxy. These disks manifest themselves as triangular pyramids and organize themselves to conform to the six-fold symmetry of the ZnO epilayer underneath with the base edges along 〈1 1 0 0〉 and side facets of {1 2 1 6}. Atomic-force microscopy measurements show a size distribution with base width centered at 140 and 24 nm height, the height/width ratio remaining constant due to the formation of special facets. Cathodoluminescence studies reveal a strong near-band-gap emission from the regions with a high density of pyramids.

ZnSe heteroepitaxial layers have been grown on GaAs (100), (110) on axis, and (110) 6° miscut substrates by molecular beam epitaxy. ZnSe on GaAs (110) shows smooth and featureless spectra from Rutherford backscattering channeling measurements taken along major crystalline directions, whereas ZnSe on GaAs (100) without pre-growth treatments exhibit large interface disorder in channeling spectra. ZnSe films grown on GaAs (110) on axis show facet formation over a wide range of growth conditions. The use of (110) 6° miscut substrates is shown to suppress facet formation; and under the correct growth conditions, facet-free surfaces are achieved. Etch pit density measurements give dislocation densities for ZnSe epitaxial layers grown on GaAs (100), (110) on axis, and (110) 6° miscut substrates of 107/cm2, 3 × 105/cm2 and 5 × 104/cm2, respectively. These results suggest that with further improvements to ZnSe growth on GaAs (110)-off substrates it may be possible to fabricate defect free ZnSe based laser devices.

ZnO single crystal thin films were grown by plasma enhanced molecular beam epitaxy on (0 0 0 1) sapphire. The growth modes of ZnO epilayers were investigated by reflection high-energy electron diffraction. A transition from two-dimensional nucleation to three-dimensional nucleation is found at the initial growth stage. Optical properties of the films, studied by photoluminescence spectroscopy, exhibit a dominant bound exciton emission at 3.361 eV at 4 K, and a deep level emission centered at 2.42 eV which is associated with either impurities or native defects. The deep level emission which is successfully suppressed to 1 500 of intensity of the excitonic emission. Fabrication of these high-quality ZnO epilayers had lead to observation of stimulated emission at room temperature.

Low-temperature studies of Cd(Zn)Se single quantum well lasers are reported. The MOVPE-grown samples lase in the true blue spectral region under pulsed nitrogen laser excitation. A microscopic technique allows accurate control of both the size and shape of the excited area. It has been possible to isolate high quality regions of a given sample for gain measurements. Thresholds of order 1 kW cm−2 are routinely obtainable. The microscopic approach also allows a convincing display of temporally stable mode strcture. In this presentation, we emphasise the stimulated emission spectra of samples selectively excited at very high intensity (up to 1000 times the laser threshold). At moderate levels of overstimulation the well emission broadens and its peak shifts to higher energy. The peak shift saturates at 25 meV. Upon saturation of the well, two distinct bands appear at higher energy. One of these corresponds in energy to the P-band of ZnSe, while the other shows the spectral characteristics of a 2D electron-hole plasma. We discuss these results in terms of the dynamics of carrier interchange between well and barrier.

We report the first optical results due to the effects of two-dimensional (2D) chirality. Using electron beam lithography we have fabricated arrays of metallic planar chiral structures on dielectric substrates, with characteristic dimensions in the near infra-red, and observed the effects of their chirality on the polarization states of diffracted light. The results showed strong polarization effects, with the handedness of the individual elements having a direct effect on the sense and magnitude of rotation of the diffracted light. We believe such structures could, in the future, form the core of a new class of meta-materials with refractive indices engineered to suit individual optical applications.

The scattering properties of a plasmonic array can be reinforced by placing the array near a planar reflector. Finite- Difference-Time-Domain (FDTD) simulations have been used to demonstrate the key design challenge of modulating the electric field that drives the plasmonic scattering, by varying the distance of a single Ag nanodisc from a Ag reflector. We show that the thickness of the dielectric separation layer plays a critical role in determining the spectral characteristics and the intensity of the power scattered by a Ag nanodisc near a reflector. A possible application of the designed structure as a plasmonic light-trap for thin Si solar cells is also experimentally demonstrated. Electron-beam lithography has been used to fabricate a pseudo-random array of 150nm plasmonic Ag nanodiscs on SiO 2 on a Ag reflector substrate. The plasmonic reflector shows a high diffuse reflectance of ~54% in the near-infrared, near-bandgap 600-900nm wavelength region for thin Si solar cells, with a low broadband absorption loss of ~18%. Wavelength-angle resolved scattering measurements indicate an angular scattering range between 20° to 80° with maximum intensity of the scattered power in the 20° to 60° angular range.

We present a hybrid waveguide-based optical switch using n-ZnO/p-Si heterojunction diode structure. The n-ZnO/p-Si vertical diode is incorporated with a Fabry-Perot microcavity to realize optical switching through electrical biasing. The ZnO layer functions as n-type transparent oxide semiconductor and waveguide cladding. Under 4V reverse bias (depletion), simulation shows a modulation depth of 5.54dB and tunable red-shift of 4nm over a cavity length of 17µm. A Fabry-Perot microcavity of 20µm length has been fabricated and measurement shows a tunable blue-shift of 0.1nm under 10V forward bias condition (accumulation).

A plasmonic back reflector has been fabricated for light-trapping application in thin film Si photovoltaic devices. The back reflector comprises of a 2D array of self-organized Ag NPs separated from a planar Ag mirror by a ZnO layer deposited by atomic-layer deposition. The diffuse reflectance and parasitic absorption losses can be modulated by varying the ZnO thickness. A maximum diffuse reflectance peak value of 30% at 950 nm, with a bandwidth of 400nm, is observed for ∼100 nm diameter NPs at a distance of 50 nm from the Ag mirror. Finite-difference time-domain simulations of a 100nm Ag sphere near a mirror were used to understand the experimentally observed trends in diffuse reflectance and parasitic absorption, with distance from the mirror. Particles very close to the mirror can couple to delocalized surface plasmons or exhibit Fano resonance effects, thereby increasing parasitic absorption. Particles situated away from the mirror are influenced by driving-field effects due to the interaction of incident and reflected photons, which modulate the scattering cross-section.

We propose a hybrid waveguide-based optical switch using n-ZnO on p-Si heterojunction structure. Under depletion-mode, the modulation depth of 6.37dB and tunable red-shift of 4 nm over cavity length of 20µm have been achieved.

The optical properties of metal nanoparticles are explored as a function of lateral size, shape,aspect-ratio and metal type. Simulations based on the discrete dipole approximation are compared with experimental measurements of arrays of metal nanoparticles fabricated by electron-beam lithography. Careful selection of experimental parameters ensures minimization of far-field and near-field coupling, and inhomogeneous broadening, thus allowing comparison with single particle simulations. The optical properties of Au nanoparticles are compared with similar Al nanoparticles for each particle type. For solar cell light-trapping applications, we require metal nanoparticles that exhibit extinction peaks near the band-edge region of the absorbing material, as well as low absorption and large optical cross-sections. Al nanoparticles are shown to be of interest for amorphous silicon solar cells, but their applications for polycrystalline solar cells is limited by the presence of an interband region in the near-infrared. The opposite is found for Au nanoparticles, which feature an interband threshold region in the visible that makes their optical properties unsuitable for amorphous silicon but very suitable for crystalline and polycrystalline silicon solar cells.

The Oriental hornet worker correlates its digging activity with solar insolation. Solar radiation passes through the epicuticle, which exhibits a grating-like structure, and continues to pass through layers of the exo-endocuticle until it is absorbed by the pigment melanin in the brown-colored cuticle or xanthopterin in the yellow-colored cuticle. The correlation between digging activity and the ability of the cuticle to absorb part of the solar radiation implies that the Oriental hornet may harvest parts of the solar radiation. In this study, we explore this intriguing possibility by analyzing the biophysical properties of the cuticle. We use rigorous coupled wave analysis simulations to show that the cuticle surfaces are structured to reduced reflectance and act as diffraction gratings to trap light and increase the amount absorbed in the cuticle. A dye-sensitized solar cell (DSSC) was constructed in order to show the ability of xanthopterin to serve as a light-harvesting molecule.

We present the comprehensive characterization of several experimental ZnO:Al films for thin film solar cell applications. The morphological and optical properties of these films are determined using traditional and new, experimental measurement techniques and results are compared to those of the commercial Asahi U-type TCO as well as samples of planar TCOs coated in silver nanoparticles. Results show that the textured ZnO:Al films provide far superior scattering to the commercial alternatives studied. Nanoparticle coated planar TCOs also show scattering enhancement with results suggesting that nanoparticle layers could be tuned to predominantly scatter light within a chosen wavelength range.

We have experimentally and theoretically demonstrated plasmonic couplers based on metal nanoparticles film (metal islands) deposited upon the optical dielectric waveguide. These nanoparticles forward scatter radiation into the optical waveguide that would otherwise be reflected and transmitted. Design, fabrication and optimisation of the plasmonic silver islands and tantalum pentoxide waveguide are reported. Broadband characteristics of light transmission showing plasmons excitation have been measured and in good agreement with simulated results from 400 nm to 800 nm. Coupling spectrum up to 15% is measured for the plasmonic coupler and in good agreement with the simulated results.

Nanostructured moth-eye antireflection schemes for silicon solar cells are simulated using rigorous coupled wave analysis and compared to traditional thin film coatings. The design of the moth-eye arrays is optimized for application to a laboratory cell (air–silicon interface) and an encapsulated cell (EVA-silicon interface), and the optimization accounts for the solar spectrum incident on the silicon interface in both cells, and the spectral response of both types of cell. The optimized moth-eye designs are predicted to outperform an optimized double layer thin film coating by approximately 2% for the laboratory cell and approximately 3% for the encapsulated cell. The predicted performance of the silicon moth-eye under encapsulation is particularly remarkable as it exhibits losses of only 0.6% compared to an ideal AR surface

A regular hexagonally packed biomimetic moth-eye antireflective surface acts as a diffraction grating at short wavelengths of the visible spectrum and shallow angles of incidence. These gratings display strong backscattered iridescence with 6-fold optical symmetry. The optical symmetry of real moth eyes is effectively infinite as nature utilizes large number of uniquely orientated domains. In this work we report on a biomimetic moth-eye surface created via nanosphere lithography with a very large distribution of close-packed tessellated domains and the resulting optical symmetry is compared to that of another widely known highly isotropic diffraction grating, also inspired by nature, the sunflower pattern. A white-light laser reflectometry system is used to measure and compare the diffraction pattern isotropy from both structures. The tessellated close-packed structure diffraction pattern approaches that of infinite optical symmetry even though the underlying pattern only possesses a six-fold symmetry. Hence, the angular isotropy observed for the sunflower pattern is replicated to a large extent via a self-assembly procedure, whilst circumventing the complicated design and manufacturing requirements of the sunflower pattern.

The photoluminescence of thin film CdS on glass grown by pulsed laser deposition is presented in the temperature range 4–300 K. The radiative recombination at the fundamental transition refers to band-to-band transitions leading to a peak centered at 2.48 eV at 300 K. A peak at such a high energy is not observed with single crystals and thin films formed by different techniques showing peaks at 2.42 and around 2.21 eV. In addition, optically pumped laser action at 2.48 eV at 300 K is demonstrated. The feedback is provided by self-formed microcavities within the hexagonal lattice of the samples.

The eyes and wings of some species of moth are covered in arrays of subwavelength pillars that have been tuned over millions of years of evolution to reflect as little sunlight as possible. We are investigating ways of exploiting this to reduce reflection from the surfaces of silicon solar cells. Here, we report on the experimental realization of biomimetic antireflective moth-eye arrays in silicon using a technique based on nanoimprint lithography and dry etching. Areas of 1cm x 1cm have been patterned and analysis of reflectance measurements predicts a loss in the performance of a solar cell of only 6.5% compared to an ideal antireflective coating. This compares well with an optimized single layer Si3N4 antireflective coating, for which an 8% loss is predicted.

Broadband antireflection schemes for silicon surfaces based on the moth-eye principle and comprising arrays of subwavelength-scale pillars are applicable to solar cells, photodetectors, and stealth technologies and can exhibit very low reflectances. We show that rigorous coupled wave analysis can be used to accurately model the intricate reflectance behavior of these surfaces and so can be used to explore the effects of variations in pillar height, period, and shape. Low reflectance regions are identified, the extent of which are determined by the shape of the pillars. The wavelengths over which these low reflectance regions operate can be shifted by altering the period of the array. Thus the subtle features of the reflectance spectrum of a moth-eye array can be tailored for optimum performance for the input spectrum of a specific application.

We report what is believed to be the first observation of lasing of an optically pumped thin CdS film formed by laser ablation on glass. Laser action is observed at room temperature, and the emission peak is at 501 nm. X-ray diffraction shows that the polycrystalline films are of wurtzite structure and have (002) preferred orientation. Fabry-Perot laser modes are spaced 16 nm apart, indicating a cavity length of 2.9mum . The cavity is formed by consistently self-formed microcavities within the hexagonal lattice.

We present a study of antireflective schemes and their operation over a full day. We compare simulation results for single and double layer antireflective coatings with bio-mimetic moth-eye structures, taking into account the full range of wavelengths and incident angles experienced by fixed solar cells from sunrise to sunset. We show that solar cells incorporating antireflective moth-eye arrays could produce up to 12% more energy than those employing single layer antireflective coatings

Enantiomeric-sensitive optical polarization conversion has been observed in the near-field above a planar chiral nanostructures consisting of an array of gammadions cut in a metal film. Formation of the far-field scattered light rotated with respect to the incident linear polarized light has been visualized.

We have extended our research to the study of near-field polarization effects arising from the planar chirality. The interaction between the neighboring elements in a metallic structure can be visualized with near-field measurements. Coupling between metallic gammadions that gives rise to the scattered electromagnetic field with polarization components different from the polarization state of the incident light can be directly identified. We have also investigated far-field effects in two-dimensional gratings consisting of regular patterns of dielectric gammadions on a silicon substrate.

We have demonstrated how dielectric planar chiral surfaces can both modulate the intensity and change the polarization state of visible light diffracted from patterned surfaces. These effects are shown to be dependent on the sense of chirality of the surface and the input polarization state of the light. Individual diffracted beams can show variations of over 30% in their intensities for different input polarization states while opposite enantiomeric structures can exhibit differences of over 50%.The size of these effects could make these surfaces particularly promising candidates for the development of solid-state polarization-state detectors.

Simple II–VI laser cavities were formed by cleaving epitaxial ZnSe samples containing a single CdSe quantum well of mean thickness about 1 monolayer. Time‐integrated stimulated emission spectra of these lasers show little evidence of mode structure. A video camera enables temporal resolution of the stimulated emission spectra. Mode structure appears on the time‐resolved spectra. In addition, however, video spectroscopy reveals spatial variations of wavelength and intensity in the laser output which are not well understood.

We report a study of the optical properties of silicon moth-eye structures using a custom-made fully automated broadband spectroscopic reflectometry system (goniometer). This measurement system is able to measure specular reflectance as a function of wavelength, polar incidence angle and azimuth orientation angle, from normal to near-parallel polar incidence angle. The system uses a linear polarized broadband super-continuum laser light source. It is shown that a moth-eye structure composed of a regular array of protruding silicon rods, with finite sidewall angle reduces reflectance and sensitivity to incident wavelength in comparison to truly cylindrical rods with perpendicular sidewalls. It is also shown that moth-eye structures have omnidirectional reflectance properties in response to azimuth orientation of the sample. The importance of applying the reflectometer setup to study the optical properties of solar cell antireflective structures is highlighted.

The eyes and wings of some species of moth are covered with arrays of nanoscale features that dramatically reduce reflection of light. There have been multiple examples where this approach has been adapted for use in antireflection and antiglare technologies with the fabrication of artificial moth-eye surfaces. In this work, the suppression of iridescence caused by the diffraction of light from such artificial regular moth-eye arrays at high angles of incidence is achieved with the use of a new tiled domain design, inspired by the arrangement of features on natural moth-eye surfaces. This bio-mimetic pillar architecture contains high optical rotational symmetry and can achieve high levels of diffraction order power reduction. For example, a tiled design fabricated in silicon and consisting of domains with 9 different orientations of the traditional hexagonal array exhibited a ~96% reduction in the intensity of the -1 diffraction order. It is suggested natural moth-eye surfaces have evolved a tiled domain structure as it confers efficient antireflection whilst avoiding problems with high angle diffraction. This combination of antireflection and stealth properties increases chances of survival by reducing the risk of the insect being spotted by a predator. Furthermore, the tiled domain design could lead to more effective artificial moth-eye arrays for antiglare and stealth applications.

The influence of driving field interference on light scattering is demonstrated for arrays of randomly arranged silver nanodiscs near a silver mirror. The peak driving field intensity is spectrally tuned by varying the separation distance between the nanodisc array and the mirror, while the plasmonic resonance position is tuned by modifying the nanodisc diameter. Scattering is maximized when the resonance position coincides with the peak driving field intensity. The optimized plasmonic mirror exhibits 60% diffuse reflectance at a wavelength of 950 nm with low (~10–12%) broadband absorption losses, for 6% surface coverage of 200-nm-diameter nanodiscs on 110 nm SiO2.

We report that planar chiral structures affect the polarization state of light in a manner similar to three-dimensional chiral (optical active) media. In experiments with artificial metal-on-silicon chiral planar gratings of 442 wallpaper group symmetry, containing millions of chiral elements per square centimeter, we observed rotation of the polarization azimuth in excess of 30 degrees of light diffracted from it. The rotation was found to change its sign for two enantiomeric forms of the media and to have components associated with both the structural arrangement and the chirality of individual structural elements.