Selective Absorption Of Light Research Articles

The role of narrow-band imaging in parathyroid surgery: a preliminary evaluation in five parathyroid adenoma cases.

Narrow-band imaging uses selective haemoglobin light absorption to emphasise vascular visualisation and capillary networks. This study aimed to evaluate the application of this technique to parathyroid surgery. This preliminary evaluation was carried out on five consecutive patients with single parathyroid adenoma being considered for minimally invasive video-assisted parathyroidectomy. The adenomas were checked for narrow-band imaging vascular patterns. Minimally invasive video-assisted parathyroidectomy was then carried out in accordance with our standard protocol. In four out of the five cases, narrow-band imaging integrated the white endoscopic light and direct vision, but in one case narrow-band imaging allowed distinction between the hidden neoplastic tissue and the surrounding structures thanks to the different vascular patterns. Narrow-band imaging was helpful in properly identifying adenoma. It is suggested that this technique be considered as a means for surgeons to improve their confidence in selected surgical treatments and to improve treatment quality.

Color Sensitive Response of Graphene/Graphene Quantum Dot Phototransistors

We present the fabrication and characterization of all-carbon phototransistors made of graphene three terminal devices, coated with atomically precise graphene quantum dots (GQD). Chemically synthesized GQDs are the light absorbing materials, while the underlying chemical vapor deposition (CVD)-grown graphene layer acts as the charge transporting channel. We investigated three types of GQDs with different sizes and edge structures, having distinct and characteristic optical absorption in the UV–vis range. The photoresponsivity exceeds 106 A/W for vanishingly small incident power (<10–12 W), comparing well with state of the art sensitized graphene photodetectors. More importantly, the photoresponse is determined by the specific absorption spectrum of each GQD, exhibiting the maximal responsivity at the wavelengths corresponding to the absorption maxima. Overall this behavior can be ascribed to the efficient and selective absorption of light by the GQDs, followed by a charge transfer to graphene, a mechanis...

Estimation of Chlorophyll-a in Northern Coastal Bay of Bengal Using Landsat-8 OLI and Sentinel-2 MSI Sensors

Chlorophyll-a can be used as a proxy for phytoplankton and thus is an essential water quality parameter. The presence of phytoplankton in the ocean causes selective absorption of light by chlorophyll-a pigment resulting in change of the ocean color that can be identified by ocean colour remote sensing. The accuracy of chlorophyll-a concentration (Chl-a) estimated from remote sensing sensors depends on the bio-optical algorithm used for the retrieval in specific regional waters. In this work, it is attempted to estimate Chl-a from two currently active satellite sensors with relatively good spatial resolutions considering ocean applications. Suitability of two standard bio-optical Ocean Colour (OC) Chlorophyll algorithms, OC-2 (2-band) and OC-3 (3-band) in estimating Chl-a for turbid waters of the northern coastal Bay of Bengal is assessed. Validation with in-situ data showed that OC-2 algorithm gives an estimate of Chl-a with a better correlation of 0.795 and least bias of 0.35 mg/m3. Further, inter-comparison of Chl-a retrieved from the two sensors, Landsat-8 OLI and Sentinel-2 MSI was also carried out. The variability of Chl-a during winter, pre-monsoon and post-monsoon seasons over the study region were inter-compared. It is observed that during pre-monsoon and post-monsoon seasons, Chl-a from MSI is over estimated compared to OLI. This work is a preliminary step towards estimation of Chl-a in the coastal oceans utilizing available better spatially resolved sensors.

Silicon carbide film-based Fabry-Pérot cavity resonance-enhanced absorption and its application for color filters

We present silicon carbide (SiC)-based Fabry-Perot (F–P) cavities which exhibit highly selective light absorption due to the strong thin film interference effect. Different configurations were discussed here by theoretically exploring the optical response of SiC film on eight metal substrates. Among them, SiC on Al, SiC on Ti and SiC on Pd F–P cavity resonators have the capacity of spectral tunability covering visible light regime, near-perfect absorption and angle dependence resistance. However, SiC on Al substrate architecture, is expected to be the optimal choice in commercial applications, harsh environment and extreme weather. The thickness-dependent properties of SiC-based resonator, in which small thickness variation will result in apparent spectra shift, was also demonstrated. Transfer-Matrix(T-M) method is introduced for calculation. Theoretical results of total round trip phase delay are in very good accordance with the simulations. We believe the SiC-based cavities have a promising application in a variety of research areas such as color filters, photovoltaic devices, no-ink printing and provide an easier way for fabrication.

Color effect of light sources on peridot based on CIE1976 L*a*b* color system and round RGB diagram system

AbstractPrevious research indicated that the peridot's color is dominated by the selective absorption of visible light caused by ferrous ion, the hue angle of which is in an inverse ratio of the concentration of Fe2+. This article focuses on the color effect of peridot under different standard light sources based on the CIE1976 L*a*b* color space system and round RGB diagram system and tries to find the best one for its grading and display. Based on the results of a series of experiments, including electron microprobe analysis, spectrophotometer, UV‐Vis spectrum, standard illumination box, and Munsell neutral color chips, it was suggested that the spectral power distribution and color temperature of a standard light source significantly influence the color of peridot in terms of lightness and chroma, particularly in the hue of peridot. As for color grading and displaying of peridot, standard light source A fails to fit in, and the color of peridot under a fluorescent light source has a higher chroma but a lower hue angle than that under daylight light source. The best choice for grading and displaying peridot is the standard light source D65. It is better to distinguish the hue of peridot when it is calculated by the round RGB diagram system.

Spectral, spatial and polarization-selective perfect absorbers with large magnetic response for sensing and thermal emission control.

Spectral, spatial, and polarization selective perfect absorption of light in periodic metal-dielectric-metal nanoslits, each of which supporting a single electric-field anti-symmetric surface mode, is systematically studied. Our numerical analysis shows complete absorption of p-polarized light associated with large magnetic field enhancement at wavelengths from the visible to the mid-infrared range and roles played by the geometrical parameters of the structure. This understanding is then applied to the design of the structure with multiple nanoslits in a period that exhibits complete absorption at multiple wavelengths. Semi-analytical expression of the zeroth mode reflectance is derived, which shows a good agreement with numerical simulations and yields clear insight into the underlying physics of light-matter interactions in the structure.

Colouration by total internal reflection and interference at microscale concave interfaces.

Many physical phenomena create colour: spectrally selective light absorption by pigments and dyes1,2, material-specific optical dispersion3 and light interference4-11 in micrometre-scale and nanometre-scale periodic structures12-17. In addition, scattering, diffraction and interference mechanisms are inherent to spherical droplets18, which contribute to atmospheric phenomena such as glories, coronas and rainbows19. Here we describe a previously unrecognized mechanism for creating iridescent structural colour with large angular spectral separation. Light travelling along different trajectories of total internal reflection at a concave optical interface can interfere to generate brilliant patterns of colour. The effect is generated at interfaces with dimensions that are orders of magnitude larger than the wavelength of visible light and is readily observed in systems as simple as water drops condensed on a transparent substrate. We also exploit this phenomenon in complex systems, including multiphase droplets, three-dimensional patterned polymer surfaces and solid microparticles, to create patterns of iridescent colour that are consistent with theoretical predictions. Such controllable structural colouration is straightforward to generate at microscale interfaces, so we expect that the design principles and predictive theory outlined here will be of interest both for fundamental exploration in optics and for application in functional colloidal inks and paints, displays and sensors.

An Optical Biosensing Strategy Based on Selective Light Absorption and Wavelength Filtering from Chromogenic Reaction.

To overcome the time and space constraints in disease diagnosis via the biosensing approach, we developed a new signal-transducing strategy that can be applied to colorimetric optical biosensors. Our study is focused on implementation of a signal transduction technology that can directly translate the color intensity signals—that require complicated optical equipment for the analysis—into signals that can be easily counted with the naked eye. Based on the selective light absorption and wavelength-filtering principles, our new optical signaling transducer was built from a common computer monitor and a smartphone. In this signal transducer, the liquid crystal display (LCD) panel of the computer monitor served as a light source and a signal guide generator. In addition, the smartphone was used as an optical receiver and signal display. As a biorecognition layer, a transparent and soft material-based biosensing channel was employed generating blue output via a target-specific bienzymatic chromogenic reaction. Using graphics editor software, we displayed the optical signal guide patterns containing multiple polygons (a triangle, circle, pentagon, heptagon, and 3/4 circle, each associated with a specified color ratio) on the LCD monitor panel. During observation of signal guide patterns displayed on the LCD monitor panel using a smartphone camera via the target analyte-loaded biosensing channel as a color-filtering layer, the number of observed polygons changed according to the concentration of the target analyte via the spectral correlation between absorbance changes in a solution of the biosensing channel and color emission properties of each type of polygon. By simple counting of the changes in the number of polygons registered by the smartphone camera, we could efficiently measure the concentration of a target analyte in a sample without complicated and expensive optical instruments. In a demonstration test on glucose as a model analyte, we could easily measure the concentration of glucose in the range from 0 to 10 mM.

Multispectral selective near-perfect light absorption by graphene monolayer using aperiodic multilayer microstructures

We investigate one-dimensional aperiodic multilayer microstructures in order to achieve near-total absorptions at preselected wavelengths in a graphene monolayer. The proposed structures are designed using a genetic optimization algorithm coupled to a transfer matrix code. Coupled-mode-theory analysis, consistent with transfer matrix method results, indicates the existence of a critical coupling in the graphene monolayer for perfect absorptions. Our findings show that the near-total-absorption peaks are highly tunable and can be controlled simultaneously or independently in a wide range of wavelengths in the near-infrared and visible ranges. The proposed approach is metal-free, does not require surface texturing or patterning, and can be also applied for other two-dimensional materials.

Doxorubicin-fucoidan-gold nanoparticles composite for dual-chemo-photothermal treatment on eye tumors.

The current research demonstrates the feasible biomedical application of AuNPs coated with doxorubicin (Dox)-loaded fucoidan (Fu) for dual-chemotherapy and photothermal treatment (PTT) on eye tumors in vitro and in vivo. Marine-derived Fu was used as a capping agent to achieve high photostability for AuNPs, and Dox as a FDA-approved anti-cancer drug was added to induce chemotherapy. The synthesized Dox-Fu@AuNPs exhibited high cytotoxicity on the tumor cells and strong light absorption for temperature increase in vitro. After intratumoral injection of Dox-Fu@AuNPs in the rabbit eye tumors, PTT-assisted Dox-Fu@AuNPs entailed the complete removal of the eye tumors without recurrence for 14 days after the treatment. Photoacoustic image contrast from the tumor regions was enhanced due to selective light absorption by the administered Dox-Fu@AuNPs. Therefore, the proposed Dox-Fu@AuNPs can be a potential nano-theranostic material for treating and diagnosing the eye tumors.

Optical properties of graphene nanocones under electric and magnetic fields

Here we present a theoretical study of the optical properties of graphene nanocones tuned by external electric and magnetic fields. We investigate the effects of the size and topology of the carbon nanostructures on the density of states and on the electro- and magneto-absorption of linearly polarized electromagnetic radiation in different nanocone geometries. We find that the electric field induces changes in the electric charge distribution mainly at the cone edges. In the infrared range the absorption coefficient shows a peculiar dependence on the electric field (magnitude and direction) and on the photon polarization for all investigated structures. Our results suggest that the electric field may be used to control the electric charge at the apex and for a selective light absorption. The presence of an axial magnetic field induces new features in the nanocone density of states due to the induced localization effects. For high fields the density of states exhibits a sequence of peaks resembling the graphene Landau spectra. The magneto-absorption spectra present a series of resonances strongly sensitive to the photon polarization opening routes for manipulation of the optical responses.

Interactions between colour-producing mechanisms and their effects on the integumentary colour palette.

Animal integumentary coloration plays a crucial role in visual communication and camouflage, and varies extensively among and within species and populations. To understand the pressures underlying such diversity, it is essential to elucidate the mechanisms by which animals have created novel integumentary coloration. Colours can be produced by selective absorption of light by skin pigments, through light scattering by structured or unstructured tissues, or by a combination of pigments and nanostructures. In this review, we highlight our current understanding of the interactions between pigments and structural integumentary tissues and molecules. We analyse the available evidence suggesting that these combined mechanisms are capable of creating colours and optical properties unachievable by either mechanism alone, thereby effectively expanding the animal colour palette. Moreover, structural and pigmentary colour mechanisms frequently interact in unexpected and overlooked ways, suggesting that classification of colours as being of any particular type may be difficult. Finally, we discuss how these mixtures are useful for investigating the largely unknown genetic, developmental and physical processes generating phenotypic diversity.This article is part of the themed issue 'Animal coloration: production, perception, function and application'.

Biocompatible astaxanthin as a novel marine-oriented agent for dual chemo-photothermal therapy.

The photothermal effect of a marine-oriented xanthophyll carotenoid, astaxanthin (AXT), was characterized based on its potential absorption of visible laser light and conversion of optical light energy into heat for thermal treatment. As an antioxidant and anticancer agent, AXT extracted from marine material can be utilized for photothermal therapy due to its strong light absorption. The current study investigated the feasibility of the marine-based material AXT to increase the therapeutic efficacy of chemo-photothermal therapy (PTT) by assessing photothermal sessions in both cells and tumor tissues. A quasi-cw Q-switched 80 W 532 nm laser system was utilized to induce thermal necrosis in in vitro and in vivo models. An in vitro cytotoxicity study of AXT was implemented using squamous cell carcinoma (VX2) and macrophage (246.7) cell lines. In vivo PTT experiments were performed on 17 rabbits bearing VX2 tumors on their eyes that were treated with or without intratumoral injection of AXT at a dose of 100 μl (300 μg/ml) followed by laser irradiation at a low irradiance of 0.11 W/cm2. Fluorescence microscopy images revealed cellular death via apoptosis and necrosis owing to the dual chemo-photothermal effects induced by AXT. In vivo experimental results demonstrated that the AXT-assisted irradiation entailed a temperature increase by 30.4°C after tumor treatment for 4 min. The relative variations in tumor volume confirmed that the tumors treated with both AXT and laser irradiation completely disappeared 14 days after treatment, but the tumors treated under other conditions gradually grew. Due to selective light absorption, AXT-assisted laser treatment could be an effective thermal therapy for various drug-resistant cancers.

Effects of red/far-red light ratio on common lamb’s-quarters, redroot pigweed, and tomato plants

Red/far-red (R/FR) ratio, a signal of impending competition from neighbouring plants, fluctuates in plant canopies because of selective absorption of red light and transmission and reflection of far-red light by leaves. The differential response of a crop and associated weeds to changes in R/FR ratio could therefore influence competitive interaction among them. In a growth chamber study, growth, morphological, and allometric responses of common lamb’s-quarters (Chenopodium album L.), redroot pigweed (Amaranthus retroflexus L.), and tomato (Solanum lycopersicum L.) seedlings to changes in R/FR ratio were investigated. Low R/FR ratio increased plant height, stem length below the first node, stem diameter, leaf length, and stem/shoot weight ratio, and decreased leaf greenness, leaf/shoot weight, and leaf/stem weight ratios in some or all of these species; the species differed significantly in this regard. Total length and surface area of tomato root were greater under low R/FR ratio. R/FR ratio did not affec...

Large-Area Low-Cost Plasmonic Perfect Absorber Chemical Sensor Fabricated by Laser Interference Lithography

We employ laser interference lithography as a reliable and low-cost fabrication method to create nanowire and nanosquare arrays in photopolymers for manufacturing plasmonic perfect absorber sensors over homogeneous areas as large as 5.7 cm2. Subsequently, we transfer the fabricated patterns into a palladium layer by using argon ion beam etching. Geometry and periodicity of our large-area metallic nanostructures are precisely controlled by adjusting the interference conditions during single- and double-exposure processes, resulting in active nanostructures over large areas with spectrally selective perfect absorption of light from the visible to the near-infrared wavelength range. In addition, we demonstrate the method’s applicability for hydrogen detection schemes by measuring the hydrogen sensing performance of our polarization independent palladium-based perfect absorbers. Since palladium changes its optical and structural properties reversibly upon hydrogenation, exposure of the sample to hydrogen caus...

Ambient exposure of the ocular tissues to optical radiation

SummaryOptical radiation is usually considered as radiation between 1 nm and 1 mm. The visible part of optical radiation typically extends from 400 and 760 nm. Optical radiation with wavelengths shorter than visible is referred to as ultraviolet radiation (UVR) and optical radiation with wavelengths longer than visible as infrared radiation (IRR). The most abundant source of optical radiation on the earth is daylight sun. The spectral emission of the sun is determined by the sun temperature, 5,778 K and the atmospheric attenuation. In environments with high backhground reflection of UVR the UVR from the sun at the surface of the earth may cause photochemical damage to the human eye. Humans have continuously increased the light load on the visual system by inventions like the fire, the incandescent‐ and the halogen‐ lamp, fluorescent tubes and recently the LED lamp. The primary emission from halogen lamps and fluorescent tubes contains enough UVR to cause photochemical damage to the eye if not fitted with suitable filters. Even when fitted with UVR blocking filters these sources increase the load of blue light on the retina that potentially causes photochemical damage. LED lamps used for illumination typically are blue emitting diodes with fluorescent coating that provides a white light sensation to the visual system. The spectral output typically has a strong peak in the blue balanced by a broad peak in red. The blue light potentially causes photochemical damage in the retina. The deviation of the spectral distribution of the LED lamp from that of the sun challenges the color perception of the visual system in the aging eye and after cataract surgery with blue blocking IOLs due to increased selective blue light absorption. Increasing use of IRR LEDs for remote sensing and control is a potential hazard to the anterior segment of the eye.

Field-induced stretching and dynamic reorientation of functionalized multiwalled carbon nanotube aggregates in nematic liquid crystals

Multiwalled carbon nanotubes (MWCNTs) exhibited distinct electrical stretching behavior in nematic liquid crystals (NLC) depending on nanotube surface state. We found that two different samples prepared by chemical functionalization (f-CNT) and physical grinding (g-CNT) revealed distinct field dependence from each other. The threshold stretching field was lower in the f-CNT aggregates than in g-CNT aggregates. This was attributed to polar functionality induced weakened van der Waals interaction in f-CNTs, which was confirmed in infrared (IR) and Raman spectroscopy. Dynamic reorientation of f-CNTs was observed under polarized optical microscopy where f-CNTs were found to follow orientation of NLC director. Uniformly aligned f-CNTs also exhibited selective light absorption in sufficiently long transient field off-state which could find potential applications in memory and modulator devices as well as the versatile functional composites.

The Effect of Novel Low Energy Pulsed Light Combined with Galvanic Energy for Home-Use Hair Removal of Dark Skin

Background and Objectives: Permanent reduction of unwanted hair on skin types V and VI is the most challenging procedure among all hair removal technologies based on selective absorption of light or laser. The objective of this study is to evaluate the safety and efficacy of a low energy pulsed-light device combined with galvanic energy, intended for home-use hair removal on dark skin. Materials and Methods: Fifteen women with skin types V and VI and dark terminal hair in axillaarea self-administrated 6 treatments at 2 week intervals, using a hand-held IPL combined with galvanicenergy device, using HPL (Home Pulsed Light) technology. Hair count and photographs were performed pre-treatment and 1 and 3 months after the last sixth treatment. Adverse events and subject satisfaction scores were recorded. Results: All patients showed a positive clinical response to treatment, with reduction of unwanted hair. Hair counts were significantly reduced by 57.3% 1 month following last treatment and by 44.5% 3 months following last treatment. No adverse events were recorded. Subject satisfaction scores of the device usability and the treatment outcome were high. Conclusions: Low energy pulsed light combined with galvanic energy may be applied safely and effectively for at-home hair removal for people with dark skin types V and VI.

Colorful titanium oxides: a new class of photonic materials.

In this communication, a new class of photonic materials, namely, two-dimensional titanium oxide-based photonic crystals, are proposed and were fabricated with an electrochemical anodization method. The high structural periodicity of the nanostructures, and the feasible variability of the chemical compositions help to realize tunable photonic bandgaps for selective light absorption in broad wavelength regions.

Silicon colors: spectral selective perfect light absorption in single layer silicon films on aluminum surface and its thermal tunability.

Using two most abundant materials in nature: silicon and aluminum, spectral selective perfect light absorption in single layer silicon films on aluminum surface is demonstrated. Perfect light absorption is achieved due to the critical coupling of incident optical wave to the second order resonance mode of the optical cavity made of a thin silicon film on aluminum surface. Spectral selective perfect light absorption results in different optical colors corresponding to different thicknesses of silicon films. The device colors do not change when viewing from large angles with respect to the surface normal. Perfect absorption wavelength can be tuned over a wide wavelength range over 70 nm by thermal annealing. This new technology, which is low cost and compatible with silicon technology platform, paves the way for many applications such as optical color filters and wavelength selective photodetectors.