Incident White Light Research Articles

A Plasmonic Nanoledge Array Sensor for Selective Detection of Cardiovascular Disease Biomarkers in Human Whole Blood.

Optical sensors face challenges when detecting ultralow amounts of analytes in whole blood, including signal quenching due to optical absorption and false positives due to nonspecific binding. This study introduces gold nanoscale array features termed nanoledges (NLs), which interact with incident white light to produce a transmitted surface plasmon resonance (tSPR) signal. This extraordinary optical transmission (EOT) spectrum occurs in the near-infrared (NIR) region, thereby minimizing signal quenching caused by visible-light absorption from blood proteins and pigments. To develop a sensitive, selective, and label-free optical biosensor for detecting various levels of cardiac troponin I (cTnI) in very small volumes of whole blood samples, DNA aptamers are tethered to the NL surface, specifically binding to the cTnI biomarker. This biological binding activity alters the refractive index at the NL surface, causing a peak shift in the EOT spectrum and enabling quantification of cTnI levels. The NL array chip demonstrated high sensitivity for cTnI detection in buffer, human serum (HS), and human whole blood (HB), with detection limits of 0.079, 0.084, and 0.097 ng/mL, respectively. Control measurements using blank target mediums and those containing up to 125 ng/mL of other proteins, such as myoglobin, creatine kinase, and heparin, showed minimal interference and high specificity. The NL plasmonic array's performance in biosensing underscores its promise for clinical analysis and its potential development as a point-of-care platform for early cardiovascular disease (CVD) diagnostics.

Full-colour-sorting metalens based on guided mode resonance

Full-colour-sorting metalens using few nanostructured layers have recently generated considerable interest as high-sensitivity colour image sensors because of their reliability and high resolution. Based on the guided mode resonance principle and propagation phase modulation, a full-colour-sorting metalens is designed, which can theoretically obtain any wavelength of light from the incident white light and realize arbitrary wavelength focusing with the same focal length in the visible range. Without the loss of generality, we propose a prototype of such metalens used for sorting blue, green and red light from the visible spectrum commonly used in practical applications. The maximum focussing efficiency is over 50% with a relatively high numerical aperture of 0.7. The proposed full-colour-sorting metalens can be used in many applications, such as colour mixing, colour holography, colour filtering, wavelength division multiplexing and so on.

Plasmonic metasurface superscatters driven by infrared surface lattice resonances

We have demonstrated that plasmonic metasurfaces composed of arrays of Au bowtie nanoantennas can support an infrared bidirectional superscattering state. This state arises when the nanoantennas are coherently coupled together, forming a surface lattice resonance that efficiently guides the infrared range (1–1.6 μm) of incident broadband white light along the plane of the arrays. This process exhibits strong polarization dependence, offering an “OFF” state where a 90° rotation of the incident light polarization effectively suppresses in-plane scattering from all sides. Stokes parameters analysis is used to study the states of polarization of the scattering, demonstrating transformation into a complete depolarized state. The results emphasize the significant influence of the multipolar modes of these nanoantennas on the interference processes associated with such scattering phenomena, and their potential applications in polarization optical switching and unique beamsplitting.

Meta-Surface Slide for High-Contrast Dark-Field Imaging

A label-free microscopy technology, dark-field microscopy, is widely used for providing high-contrast imaging for weakly scattering materials and unstained samples. However, traditional dark-field microscopes often require additional components and larger condensers as the numerical aperture increases. A solution to this is the use of a meta-surface slide. This slide utilizes a multilayer meta-surface and quantum dots to convert incident white light into a red glow cone emitted at a larger angle. This enables the slide to be used directly with conventional biological microscopy to achieve dark-field imaging. This paper focuses on the design and preparation of the meta-surface and demonstrates that using the meta-surface in a standard transmission optical microscope results in a dark-field image with higher contrast than a bright-field image, especially when observing samples with micron-sized structures.

Comprehensive modeling and predicting light transmission in microalgal biofilm

Biofilm-based microalgae culture combined with wastewater treatment is a promising biotechnology for environmental management. Light availability influences the accumulation of microalgal biomass and nutrient removal. A light attenuation model which comprehensively considered microalgal biofilm structure (density and biofilm thickness), pigments content, and extracellular polymeric substances content was developed to predict the light attenuation in biofilm according to the simplification of the radiative transfer equation. The predicted results were in good overall agreement with the experiment, with an average error of less than 9.02%. These factors (biofilm density, thickness, pigments content, and extracellular polymeric substances content) all contributed to the light intensity attenuation, but biofilm thickness caused the most dramatic attenuation under the same increment of relative change in actual culture. The scattering coefficient of the biofilm (0.433 m2/g) was less than that of the suspension (1.489 m2/g) under white incident light. It suggests that the dense structure of cells allows much light to be concentrated in the forward direction when transmitting. This model could be adopted to predict the light distribution in microalgal biofilm for the further design of efficient photobioreactors and the development of light optimization strategies.

Red:Blue LED light proportion affects biomass accumulation and polyamine metabolism in Anoectochilus roxburghii studied by nano-electrospray ionization mass spectrometry

Light quality affects the plant growth, physiology, and polyamine (PA) metabolism. Anoectochilus roxburghii is an ornamental, medicinal, and culinary perennial herb in many countries. In this study, we identified the optimal light environment for enhancing the growth of A. roxburghii in vitro, and analyzed PA metabolism under blue (B), three red:blue combinations at different proportions of the total incident photon flux density (R1B2: the ratio of 1: 2, R1B1: the ratio of 1: 1, and R2B1: the ratio of 2: 1, respectively), red (R), and white light (W) environment for 120 days. The biomass accumulation and stomata characteristics were evaluated, as well as total phenolic, total flavonoids, soluble sugars, and soluble proteins. Besides, nine PA compounds were quantitatively analyzed by nano-electrospray ionization mass spectrometry (nano-ESI-MS) without complex sample pretreatment. The results showed that the biomass, total phenolic, total flavonoids, soluble sugars, and soluble proteins were significantly higher in the R1B1 group, which was more conducive to stomata opening. The accumulation of the nine PA compounds increased significantly in the B and R groups, compared with W group, but decreased in the combinations of red and blue lights, especially in the R1B1 group, which A. roxburghii showed better growth. We conclude that the R1B1 could be used as the optimal growth light environment of A. roxburghii tissue culture. Nano-ESI-MS could be used as a rapid and sensitive method to quantify PAs, providing new data for enhancing our understanding about the functions of PAs in plant-light environment interactions.

Programmable nonreciprocal meta-prism

Optical prisms are made of glass and map temporal frequencies into spatial frequencies by decomposing incident white light into its constituent colors and refract them into different directions. Conventional prisms suffer from their volumetric bulky and heavy structure and their material parameters are dictated by the Lorentz reciprocity theorem. Considering various applications of prisms in wave engineering and their growing applications in the invisible spectrum and antenna applications, there is a demand for compact apparatuses that are capable of providing prism functionality in a reconfigurable manner, with a nonreciprocal/reciprocal response. Here, we propose a nonreciprocal metasurface-based prism constituted of an array of phase- and amplitude-gradient frequency-dependent spatially variant radiating super-cells. In conventional optical prisms, nonreciprocal devices and metamaterials, the spatial decomposition and nonreciprocity functions are fixed and noneditable. Here, we present a programmable metasurface integrated with amplifiers to realize controllable nonreciprocal spatial decomposition, where each frequency component of the incident polychromatic wave can be transmitted under an arbitrary and programmable angle of transmission with a desired transmission gain. Such a polychromatic metasurface prism is constituted of frequency-dependent spatially variant transistor-based phase shifters and amplifiers for the spatial decomposition of the wave components. Interesting features include three-dimensional prism functionality with programmable angles of refraction, power amplification, and directive and diverse radiation beams. Furthermore, the metasurface prism can be digitally controlled via a field- programmable gate array (FPGA), making the metasurface a suitable solution for radars, holography applications, and wireless telecommunication systems.

Quantum Disordered States: Quantum Disordered State of Magnetic Charges in Nanoengineered Honeycomb Lattice (Adv. Sci. 6/2021)

Magnetic charges on the vertices of a two‐dimensional artificial magnetic honeycomb lattice can manifest liquid‐like quantum mechanical disorderness via charge dynamics. In article number 2004103, Deepak K. Singh, Valeria Lauter, and co‐workers demonstrate the existence of massively degenerate paramagnetic ground states at low temperature that are not greatly affected by magnetic field application. Experimental evidence, obtained using neutron reflectometry measurements (white incident light pattern), are tantamount to the occurrence of a novel quantum disordered state of magnetic charges. (Image credit: Oak Ridge National Laboratory/Jill Hemman)

Coloration of Surfaces With Periodic Microstructures Replicated by Nonisothermal Precision Molding

Abstract Micro/nanoperiodic structures are generally adopted in diffraction gratings. As an important optical component, the diffraction grating has the capability to split and diffract incident white light beams into iridescent beams dispersing to different directions. The appearance of coloration is a form of structural coloration by optical diffraction. In this paper, the nonisothermal precision molding is introduced for rapid and precise replication of periodic micro/nanograting structures, which are employed to render iridescent colors onto surfaces. First, the effect of colorization and periodic grating profiles are theoretically analyzed. Second, different periodic microgratings on silicon wafer, which are generally generated by photolithography, are employed in nonisothermal precision molding process as mold inserts. The molding result indicates that the periodic grating space and depth of grating structures can be precisely replicated from the mold inserts to polymer substrates. Subsequently, the split and iridescent color effects are demonstrated with monochromatic and white incident light beam and compared between samples with different periodic grating spaces. The optical effects of the replicated microstructures confirm the feasibility of this method. The proposed nonisothermal precision molding process provides an alternative manufacturing option for realizing structural colors with large volume and low cost.

Decreased R:FR Ratio in Incident White Light Affects the Composition of Barley Leaf Lipidome and Freezing Tolerance in a Temperature-Dependent Manner

In cereals, C-repeat binding factor genes have been defined as key components of the light quality-dependent regulation of frost tolerance by integrating phytochrome-mediated light and temperature signals. This study elucidates the differences in the lipid composition of barley leaves illuminated with white light or white light supplemented with far-red light at 5 or 15 °C. According to LC-MS analysis, far-red light supplementation increased the amount of monogalactosyldiacylglycerol species 36:6, 36:5, and 36:4 after 1 day at 5 °C, and 10 days at 15 °C resulted in a perturbed content of 38:6 species. Changes were observed in the levels of phosphatidylethanolamine, and phosphatidylserine under white light supplemented with far-red light illumination at 15 °C, whereas robust changes were observed in the amount of several phosphatidylserine species at 5 °C. At 15 °C, the amount of some phosphatidylglycerol species increased as a result of white light supplemented with far-red light illumination after 1 day. The ceramide (42:2)-3 content increased regardless of the temperature. The double-bond index of phosphatidylglycerol, phosphatidylserine, phosphatidylcholine ceramide together with total double-bond index changed when the plant was grown at 15 °C as a function of white light supplemented with far-red light. white light supplemented with far-red light increased the monogalactosyldiacylglycerol/diacylglycerol ratio as well. The gene expression changes are well correlated with the alterations in the lipidome.

Novel achromatic polariser for the homogeneously aligned nematic liquid crystal displays

ABSTRACT Recent development of optical compensation scheme for liquid crystal display (LCD) enables to realise a high quality display by eliminating the unnecessary birefringence at oblique viewing directions. However, the red colour mura in a voltage-off dark state of homogeneously aligned LCD (HA-LCD) needs to be suppressed. In this report, we propose a novel optical compensation scheme for eliminating off-axis red colour mura by utilising a negative retardation tri-acetyl cellulous (TAC) film which results in a uniform spatial deviation of polarisation states for an incident white light. The proposed compensation scheme is demonstrated in detail by performing simulations and experimental studies, and high image quality of HA-LCDs without red colour mura in the dark state is realised.

Paper-like flexible optically isotropic liquid crystal film for tunable diffractive devices.

We have demonstrated a paper-like diffractive film in which nano-structured liquid crystal droplets are embedded in elastomeric monomer incorporated polymer matrix by polymerization induced phase-separation. The film with voltage-tunable phase grating exhibits an optically isotropic phase with high transparency and an effective chromatic diffraction for an incident white light with sub-millisecond switching time. In addition, the proposed diffractive film is exhibiting excellent chemical stability against organic and inorganic solvents. In this paper, the diffraction properties of test films depending on incident polarization direction, wavelength, and spatial dispersion are characterized. Easy processing and optically isotropic nature of the film imparts potential applications to flexible electro-optic devices that can be widely implemented in wearable photonics.

In situ reflection imaging and microspectroscopic study on three-dimensional crystal growth of L-phenylalanine under laser trapping

We investigate growth behavior of an L-phenylalanine crystal formed by laser trapping with the use of reflection imaging and microspectroscopy. Optical reflection micrographs show colored images of the crystal due to constructive interference of incident white light. The color distribution on the crystal is dynamically changed under laser trapping, which is in addition to enlargement of the crystal plane area. The temporal change in the crystal thickness is examined by measuring reflection spectra of the crystal. We discuss the three-dimensional crystal growth under laser trapping by comprehensively considering the changes in crystal thickness and crystal plane area.

Colour routing with single silver nanorods

Elongated plasmonic nanoparticles have been extensively explored over the past two decades. However, in comparison with the dipolar plasmon mode that has attracted the most interest, much less attention has been paid to multipolar plasmon modes because they are usually thought to be “dark modes”, which are unable to interact with far-field light efficiently. Herein, we report on an intriguing far-field scattering phenomenon, colour routing, based on longitudinal multipolar plasmon modes supported by high-aspect-ratio single Ag nanorods. Taking advantage of the distinct far-field behaviours of the odd and even multipolar plasmon modes, we demonstrate two types of colour routing, where the incident white light can be scattered into several beams with different colours as well as different propagation directions. Because of the narrow linewidths of the longitudinal multipolar plasmon modes, there is little spectral overlap between the adjacent peaks, giving rise to outstanding colour selectivity. Our experimental results and theoretical model provide a simple yet effective picture for understanding the far-field behaviour of the longitudinal multipolar plasmon modes and the resultant colour routing phenomenon. Moreover, the outstanding colour routing capability of the high-aspect-ratio Ag nanorods enables nanoscale optical components with simple geometries for controlling the propagation of light below the diffraction limit of light.

Waveguide-Imprinted Slim Polymer Films: Beam Steering Coatings for Solar Cells

We report that transparent polymer coatings imprinted with tilted planar waveguides significantly reduce optical loss caused by the scattering of incident light by front metal contacts of solar cells. A periodic array of planar waveguides oriented at specific angles with respect to the film’s surface normal efficiently captures and steers incident light away from contacts and, in this way, suppresses scattering. These beam steering films are fabricated in a single, room temperature step by self-trapped incandescent beams. The beams inscribe multimode planar waveguides oriented at angles ranging from 0° to 2.7° inphotopolymerizable epoxide resin. We characterized the microstructural and optical properties of the films and demonstrated their ability to deflect incident white light, comparable to sunlight, by as much as 180 μm. Solar cells coated with beam steering films showed significant enhancements in external quantum efficiency (EQE) of up to 4.42% relative to unstructured films. This first demonstration of waveguide-based deflection of light from metal contacts represents a facile, inexpensive, low energy approach to EQE enhancement, which can be integrated without disrupting well-established solar cell manufacturing technologies.

Reduced Graphene Oxide-Nanostructured Silicon Photosensors with High Photoresponsivity at Room Temperature

We have created nanostructured Si (∼3 nm) with a direct band gap of 1.37 eV on electrically conducting reduced graphene oxide (rGO) for a highly efficient photosensor. This robust photosensor is fabricated using a nonequilibrium processing route, where nanosecond excimer laser pulses melt the alternating layers of Si and amorphous carbon to form micropillars and nanoreceptors of Si on rGO layers. The incident white light generates free carriers in the Si microstructures and nanoreceptors which are ballistically transported (via rGO layers) to the external circuit under the application of a voltage bias. The responsivity of rGO-Si devices to light (resistance vs time) and I–V measurements indicate an exponential drop in resistance with the incidence of white light and nonrectifying nature, respectively. Photoresponsivity of the rGO-Si devices is calculated to be 3.55 A/W at room temperature, which is significantly larger than the previously fabricated graphene-based ohmic photosensors. Temperature-dependen...

Femtosecond laser fabricated polymeric grating for spectral tuning

By taking advantages of the two-photon polymerization induced by femtosecond laser and the versatility of the femtosecond laser microfabrication, we demonstrate a femtosecond laser microfabricated polymeric grating for spectral tuning, in which gratings of different thicknesses achieve gradual tuning of a white incident light into output lights of different colors ranging from cyan to red, which is in good agreement with the simulation. Through the selection of different grating parameters, the technique developed in this study offers the possibility to tailor the performance of the grating to achieve specific grating efficiency or complete extinction at specific wavelengths, which is promising for measurements and applications in spectroscopy, sensing, integrated optical systems, and biomedicine.

Wide-Angle Polarization-Controllable Structure Color Based on Metamaterial Resonators With Polarized Multiband Absorption Peaks

The polarization-controllable structure color has been theoretically designed by utilizing metamaterial resonators with polarization-dependent multiband absorption peaks. Our designed nanostructure, consisting of the periodic circle and ellipse resonators, shows above 80% reflectivity from 502 to 553 nm (the green structure color) for TE-polarized incident white light, but above 80% reflectivity from 610 to 750 nm (the red structure color) for TM-polarized incident white light. Therefore, the structure colors gradually change from green to red when the polarization angles increasing from 0° (TE) to 90° (TM). The polarization-controllable structure colors come from the polarization-dependent multiband absorption peaks. When the polarization changes from TE to TM, the absorption peaks shift from 454, 624, and 714 nm to 454, 498, and 550 nm. The physical mechanism is explained by the electromagnetic fields distribution and the equivalent LC circuit model. It can keep the structure color for a wide incident angle.

Laser induced ripples’ gratings with angular periodicity for fabrication of diffraction holograms

Laser induced ripples (also known as Laser Induced Periodic Surface Structures, LIPSS) have gained a considerable attention by both researchers and industry due to their surface functionalization applications. These ripples act as diffraction gratings for the visible light therefore it is widely used in some optical applications and color marking. In this research, a method is proposed for producing holograms by varying the ripples’ orientation along the beam path during the laser scanning and thus producing a pattern of ripples orientations. It was demonstrated that, by employing this method, it was possible to produce linear and radial pattern of gratings by changing the ripples’ orientations following a given periodic function. As a result, smooth transitions of diffracted monochromatic light along the beam path were achieved, especially in diffracting colors from different locations when changing the azimuthal and incident angles of the incident white light. In addition, the reflection of polarized white light by such periodic gratings was investigated and it was shown that it was fully dependent on the ripples’ orientations in respect to the light linear polarization vector.

Magnetically tunable oil droplet lens of deep-sea shrimp

In this study, the tunable properties of a bio-lens from a deep-sea shrimp were investigated for the first time using magnetic fields. The skin of the shrimp exhibited a brilliantly colored reflection of incident white light. The light reflecting parts and the oil droplets in the shrimp’s skin were observed in a glass slide sample cell using a digital microscope that operated in the bore of two superconducting magnets (maximum strengths of 5 and 13 T). In the ventral skin of the shrimp, which contained many oil droplets, some comparatively large oil droplets (50 to 150 μm in diameter) were present. A distinct response to magnetic fields was found in these large oil droplets. Further, the application of the magnetic fields to the sample cell caused a change in the size of the oil droplets. The phenomena observed in this work indicate that the oil droplets of deep sea shrimp can act as lenses in which the optical focusing can be modified via the application of external magnetic fields. The results of this study will make it possible to fabricate bio-inspired soft optical devices in future.