Narrow-band Light Research Articles

National Institute of Standards and Technology transportable tunable ultraviolet laser irradiance facility for water pathogen inactivation.

A method of ultraviolet germicidal irradiation (UVGI) for water pathogen inactivation effectiveness using tunable, narrowband laser light is described. A transportable tunable UV (TTUV) laser system for providing a known irradiance (μW/cm2) or dose (mJ/cm2) suitable for irradiating water samples in Petri dishes over the wavelength range of 210 nm-300 nm was developed by the National Institute of Standards and Technology. The TTUV facility, consisting of a 1 kHz pulsed UV laser and light-tight enclosure containing the optics necessary to uniformly irradiate a water sample, was used in a microbiology laboratory to dose drinking water pathogens and surrogates as part of a Water Research Foundation study in the summer and fall of 2012. The approach demonstrated improved accuracy and simplified spectral analysis over conventional pathogen inactivation sources consisting of broadband UV sources and bandpass filters. In this work, the TTUV facility design and key components are described, including modifications in the field to provide the required irradiance levels. The irradiance and dose levels produced by the tunable UV laser during the project are also presented. The transportability of the TTUV system enabled it to be brought to a microbiology facility allowing the water samples (microbial suspensions) to be irradiated in a location with experienced staff and facilities for preparing, handling, analyzing, storing, and shipping the many samples studied. These results, published elsewhere, established that the tunable UV laser system provides unique UVGI capabilities for use with water pathogens and has applications for other pathogen experiments, for example, air-purification studies.

Efficiency increase in multijunction monochromatic photovoltaic devices due to luminescent coupling

We present a multijunction detailed-balance model that includes the effects of luminescent coupling, light trapping, and nonradiative recombination, suitable for the treatment of multijunction solar cells and photonic power converters—photovoltaic devices designed to convert the narrow-band light. The model includes both specular and Lambertian reflections using a ray-optic formalism and treats nonradiative processes using an internal radiative efficiency. Using this model, we calculate and optimize the efficiency of multijunction photonic power converters for a range of material qualities and light-trapping schemes. Multijunction devices allow increased voltage with lower current, decreasing series resistance losses. We show that efficiency increases significantly with an increased number of junctions, even without series resistance, when the device has an absorbing substrate. Such an increase does not occur when the device has a back reflector. We explain this effect using a simplified model, which illustrates the origin of the decreased radiative losses in multijunction devices on substrates.

732 Clinical efficacy analysis of narrow spectrum intense pulsed light in the treatment of acne-related erythema in Chinese patients

Objective: To evaluate the efficacy and safety of Dye narrow-band pulsed light (DPL) in the treatment of Acne Vulgaris in Chinese patients. Methods: The clinical data of 50 patients with erythema after facial acne who had received treatment in the Hospital between January 2019 to June 2019 were analyzed.50 patients with acne-related erythema, aged 15 to 36 years, with a course of 2 to 6 years, with an average of 2.6 years. The following conditions are excluded: (1) a viral infection on the face or the wound incision has not healed; (2) a history of photosensitivity or taking photosensitivity drugs within 4 weeks; (3) patients who have taken oral retinoic acid in the past six months; (4) pregnancy and actating women; (5) patients with heart, kidney, liver insufficiency or other serious underlying diseases; (6) patients with mental illness. Using Harmony XL and Dye-PL hand tools at wavelengths of 500 to 600 nm (Alma Lasers, Caesarea, Israel), 50 patients with post-acne Erythema were treated 3 times at 4-week intervals. The degree of facial erythema, skin brightness, the degree of pain during treatment, and the adverse reactions after treatment were measured and recorded before each treatment and at 2 weeks after treatment. Basic Cure: improvement ≥90%; marked effect: improvement ≥60%; progress: improvement ≥30%; invalid: improvement <30%. Results: 50 patients completed treatment and follow-up. The effective rate of DPL for treating acne-related erythema was 100%, and the erythema and pigments were improved to varying degrees without serious adverse reactions. Conclusion: Narrow spectrum intense pulsed light is effective in the treatment of post-acne Erythema with few side effects, short recovery time and good tolerance. DPL has a good clinical application prospect.

Engineering Edge States of Graphene Nanoribbons for Narrow-Band Photoluminescence.

Solid-state narrow-band light emitters are on-demand for quantum optoelectronics. Current approaches based on defect engineering in low-dimensional materials usually introduce a broad range of emission centers. Here, we report narrow-band light emission from covalent heterostructures fused to the edges of graphene nanoribbons (GNRs) by controllable on-surface reactions from molecular precursors. Two types of heterojunction (HJ) states are realized by sequentially synthesizing GNRs and graphene nanodots (GNDs) and then coupling them together. HJs between armchair GNDs and armchair edges of the GNR are coherent and give rise to narrow-band photoluminescence. In contrast, HJs between the armchair GNDs and the zigzag ends of GNRs are defective and give rise to nonradiative states near the Fermi level. At low temperatures, sharp photoluminescence emissions with peak energy range from 2.03 to 2.08 eV and line widths of 2-5 meV are observed. The radiative HJ states are uniform, and the optical transition energy is controlled by the band gaps of GNRs and GNDs. As these HJs can be synthesized in a large quantity with atomic precision, this finding highlights a route to programmable and deterministic creation of quantum light emitters.

1-D Metal-Dielectric-Metal Grating Structure as an Ultra-Narrowband Perfect Plasmonic Absorber in the Visible and Its Application in Glucose Detection

The need for an easy to fabricate perfect and narrowband light absorber in the visible range of electromagnetic (EM) spectrum has always been in demand for many scientific and device applications. Here, we propose a metal-dielectric-metal (MDM) 1-D grating plasmonic structure as a perfect narrow band light absorber in the visible and its application in glucose detection. The proposed structure consists of a 1- D grating of gold on the top of a dielectric layer on a gold film. Optimization for dielectric grating index (n), grating thickness (t), grating width (W), and grating period (P) has been done to improve the performance of plasmonic structure by calculating its quality factor and figure-of-merit (FOM). The optimized plasmonic structure behaves as a perfect narrowband light absorber. The flexibility to work at a specific wavelength is also offered by the proposed structure through an appropriate selection of the geometrical parameters and refractive index of the dielectric grating. The equivalent RC model is used to understand different components of the proposed structure on the optical response. The absorption response of the structure is invariant to the incident angle. Moreover, the calculated absorbance of the proposed plasmonic structure is ~ 100% with a narrow full-width half maxima (FWHM) of ~ 2.8 nm. We have numerically demonstrated a potential application of the proposed MDM absorber as a plasmonic glucose sensor in the visible range with detection sensitivity in the range of 140 to 195 nm/RIU.

Rhodopsin and melanopsin contributions to human brightness estimation.

We examined the contributions of rhodopsin and melanopsin to human brightness estimation under dim lighting. Absolute brightness magnitudes were estimated for full-field, rhodopsin-, or melanopsin-equated narrowband lights (${\lambda _{\rm max}}:\;{462}$λmax:462, 499, 525 nm). Our data show that in scotopic illumination ($ - {5.1}$-5.1 to $ - {3.9}\;{\log}\;\unicode{x00B5} {\rm Watts}\cdot{\rm cm}^{ - 2}$-3.9logµWatts⋅cm-2), the perceptual brightness estimates of rhodopic irradiance-equated conditions are independent of their corresponding melanopic irradiance, whereas brightness estimates with melanopic irradiance-equated conditions increase with increasing rhodopic irradiance. In mesopic illumination ($ - {3.4}$-3.4 to $ - {1.9}\;{\log}\;\unicode{x00B5} {\rm Watts}\cdot{\rm cm}^{ - 2}$-1.9logµWatts⋅cm-2), the brightness estimates with both lighting conditions increase with increasing rhodopic or melanopic irradiances. Rhodopsin activation therefore entirely signals scotopic brightness perception and plateaus in mesopic illumination where intrinsic melanopsin contributions become first evident. We infer that all photoreceptor signals are transmitted to higher visual centers for representing scene brightness in scotopic and mesopic illumination through both conventional and melanopsin ganglion cell pathways.

Temporal imaging for ultra-narrowband few-photon states of light

Plenty of quantum information protocols are enabled by manipulation and detection of photonic spectro-temporal degrees of freedom via light–matter interfaces. While present implementations are well suited for high-bandwidth photon sources such as quantum dots, they lack the high resolution required for intrinsically narrowband light–atom interactions. Here, we demonstrate far-field temporal imaging based on ac-Stark spatial spin-wave phase manipulation in a multimode gradient echo memory. We achieve a spectral resolution of 20 kHz with MHz-level bandwidth and an ultralow noise equivalent to 0.023 photons, enabling operation in the single-quantum regime.

Insight into the Liquid Structure of Water and Sodium Chloride Solutions Using Stimulated Raman Scattering

By dissolving sodium chloride ($\mathrm{Na}\mathrm{Cl}$) in liquid water, we realize an obvious enhancement of stimulated Raman scattering (SRS). Compared with pure water, the performance improvements include spectrum purification, an increased Raman gain, a decreased pump threshold, and an increased conversion efficiency. In the best SRS results, the pump threshold decreases by 45% and the maximum conversion efficiency increases by 10.4%. Then, water becomes a typical Raman-scattering medium that generates narrowband light. Moreover, we find that the bulk structure of water and $\mathrm{Na}\mathrm{Cl}$ solutions can be analyzed in detail by combining the principles of SRS and analysis of the SRS spectra. In water, the $\mathrm{O}---\mathrm{H}$ stretching band is proved to be a superposition of stretching modes of different water clusters. For the solution, the $\mathrm{O}---\mathrm{H}$ stretching vibration of water molecules in hydration shells around ${\mathrm{Cl}}^{\ensuremath{-}}$ ions can be obtained directly, and its variation with respect to solute concentration is investigated using SRS spectra. The superior SRS properties of solutions originate from the hydration shell around the ${\mathrm{Cl}}^{\ensuremath{-}}$ ions. This work suggests that SRS is a promising approach to identifying structures in water and $\mathrm{Na}\mathrm{Cl}$ solutions, and that it can easily be extended to other liquids and solutions.

Coherent narrowband light source for ultrafast photoelectron spectroscopy in the 17-31 eV photon energy range.

Here, we report on a novel narrowband High Harmonic Generation (HHG) light source designed for ultrafast photoelectron spectroscopy (PES) on solids. Notably, at 16.9 eV photon energy, the harmonics bandwidth equals 19 meV. This result has been obtained by seeding the HHG process with 230 fs pulses at 515 nm. The ultimate energy resolution achieved on a polycrystalline Au sample at 40 K is ∼22 meV at 16.9 eV. These parameters set a new benchmark for narrowband HHG sources and have been obtained by varying the repetition rate up to 200 kHz and, consequently, mitigating the space charge, operating with electrons/s and photons/s. By comparing the harmonics bandwidth and the ultimate energy resolution with a pulse duration of ∼105 fs (as retrieved from time-resolved experiments on bismuth selenide), we demonstrate a new route for ultrafast space-charge-free PES experiments on solids close to transform-limit conditions.

Источники двухволнового узкополосного излучения на основе алмазных наночастиц с введенными одновременно центрами окраски германий-вакансия и кремний-вакансия

Diamond particles with germanium-vacancy and silicon-vacancy color centers were synthesized by Hot Filament Chemical Vapor Deposition technique. The next step was the reactive ion-plasma etching of the particles. As a result, the diamond nanoparticles were obtained whose photoluminescence spectra consist of two narrow intense zero phonon lines of the embedded centers. Such fluorescent diamond nanoparticles are promising as dual-wavelength narrow-band light emitters for luminescent nanothermometry.

Simultaneously performing optical and electrical responses from a plasmonic sensor based on gold/silicon Schottky junction.

Making the chemical or biological sensors simpler and more compatible with other measurements is a key enabling technology for commercial application. In this work, we propose a plasmonic refractive-index sensor only based on gold/silicon Schottky junction to simultaneously perform optical and electrical read-out responses. Via exciting surface plasmon resonance (SPR), the designed device shows a few characteristic reflection valleys and greatly enhances the narrowband light absorption. Calculated results indicate that the SPR resonance wavelength can be tuned in the wavelength range of 1100-2000 nm by manipulating the period, width of the Si nanochannel and the incident angle of light. When the analyte is changed, the SPR resonance wavelength generated at the bottom surface of the Au layer barely shifts, while the one at the top surface shows a significant linear shift. The optimally designed system shows an optical response with a refractive index sensitivity of over 1000 nm per refractive index unit (nm/RIU). Moreover, the electrodynamic calculation of the hot electrons predicts the electrical response can be up to 14.5 mA/(W·RIU) for an example of detecting trichloromethane, where the employed light can be a monochromatic light and the sensing operation can be much simpler relative to the conventional spectral work mode.

Thermal stability and photoluminescence of Mn2+ activated green-emitting feldspar phosphor SrAl2Si2O8: Mn2+ for wide gamut w-LED backlight

An oxide-based green emitting phosphor, SrAl2Si2O8: Mn2+ (SASO: Mn2+) deriving from the feldspar mineral model has been successfully synthesized by a facile solid-state reaction. Upon 450 nm blue-light excitation, brightness narrow-band green light peaking at 517 nm with a full-width at half-maximum (fwhm) of 26 nm can be obtained. Owing to the narrow band emission, the CIE chromaticity coordinates are (0.182, 0.745) and the color purity of SASO: Mn2+ is determined to be 78.3%. Meanwhile, the internal quantum efficiency (IQE) of the representative sample can reach up to 45.6% under 450 nm. In addition, the phosphor exhibits an extremely thermal stability, i.e., the integrated emission intensity at 420 K still remains 92% of the initial value. Furthermore, w-LED device fabricated from optimized phosphor SASO: Mn2+ (green), commercial phosphor KSF: Mn4+ (red) and blue LED chip can cover 120% National Television System Committee standard (NTSC) value. All these results suggest that the Mn2+ ion activated green emitting phosphor has great potential for wide gamut w-LEDs backlights.

Manganese(II) in Tetrahedral Halide Environment: Factors Governing Bright Green Luminescence.

Finding narrow-band light emitters for the visible spectral region remains an immense challenge. Such phosphors are in great demand for solid-state lighting and display application. In this context, green luminescence from tetrahedrally coordinated Mn(II) is an attractive research direction. While the oxide–ligand environment had been studied for decades, much less systematic efforts have been undertaken with regard to halide coordination, especially in the form of fully inorganic halide matrixes. In this study, we synthesized a series of hybrid organic–inorganic Mn(II) halides as well as a range of fully inorganic Zn halide hosts (chlorides, bromides, iodides) doped with Mn(II). In the latter, tetrahedral coordination is attained via substitutional doping owing to the tetrahedral symmetry of Zn sites. We find that the choice of the halide as well as subtle details of the crystal structure profoundly govern the photoluminescence peak positions (500–550 nm range) and emission line widths (40–60 nm) as well as radiative lifetimes (shorter for iodides) through the altered ligand-field effects and degrees of spin–orbit coupling. The photoluminescence quantum yields were as high as 70–90%. The major hurdle for the practical use of these compounds lies in their low absorption coefficients in the blue spectral regions.

Manipulating the Charge Transfer Absorption for Narrowband Light Detection in the Near-Infrared

Charge generation and recombination processes at interfaces between electron donating (donor, D) and accepting molecules (acceptor, A) are mediated by intermolecular charge-transfer (CT) states. Si...

Long-term maintenance therapy with Cyclosporine A in adults with generalized pustular psoriasis

Generalized pustular psoriasis (GPP) is a rare and serious immune-mediated skin disorder that is characterized by a widespread eruption of sterile and subcorneal pustules. In the present study we investigated the efficacy of Cyclosporine A (Cy A) in treatment of 9 adults with drug-refractory GPP viz. topical Corticosteroids, retinoids, methotrexate and narrow-band ultraviolet light exposure (UVB). Initially; they were resuscitated as burn patients. Cy A was administered on day 1 at a dose of 100 mg twice daily either in the form of syrup or Neoral capsules. In most patients, skin lesions had healed by 6 weeks and the dose of Cy A was reduced to minimum to prevent further recurrence. Seven patients had required 50 mg twice daily and 2 were controlled with 50 mg am and 25 mg pm. On follow up, there was no serious relapse, liver and kidney disease. Minor complications included; hirsutism and dark skin (n: 5) and gingival hyperplasia (n: 2). Trial to replace Cy A with Tacrolimus (Prograf) failed to maintain remission. In conclusion; Cy A is a safe and effective treatment for GPP.&#x0D; Keywords: Cyclosporin A, treatment, psoriasis, pustular.

Surface profile measurement of doped silicon using near-infrared low-coherence light.

A scanning interferometry system based on near-infrared low-coherence interferometry by using a superluminescent diode (SLD) as the light source is presented. The system cannot only measure the surface profile of doped double-sided polished silicon but also measure its optical thickness and refractive index. The measurement system uses near-infrared CCD to detect interferometric light in the near infrared, based on the Michelson interference principle. SLD has low temporal and high spatial coherence and high penetration to doped silicon wafers; thus, higher visibility can be obtained when measuring the rear side. Meanwhile, the optical thickness measured by low coherent scanning interference is compared with the optical thickness obtained by spectrally resolved interferometry to verify the accuracy of the system. Due to the periodic characteristics of interference fringes, the coherence length of the narrowband light source is usually greater than the path length difference of the interferometer. It gives the measurement a phase ambiguity of 2π, which may severely limit the application of the measurement. However, the short coherent length SLD light source used in the project can avoid 2π phase ambiguity problems. Besides, this system can perform full scanning in a larger step and achieve rapid on-line measurement of the target surface.

Filterless narrowband photodetectors employing perovskite/polymer synergetic layers with tunable spectral response

Abstract Spectrally selective light detection, especially the detection within desired spectral range, is crucial for many fields, such as image sensing, optical communication, climate monitoring and national defense. Conventional narrowband photodetectors with optical filters are face to the architectural complexity and the increased device cost. Here, a smart strategy for achieving the narrowband light detection with photodetectors is proposed by employing perovskite/polymer synergetic layers, in which the perovskite layer acts as an electronically-quenching optically-active (EQOA) layer and the polymer layer acts as the active layer. The full width at half maximum of this narrowband photodetectors can reach minimum 50 nm due to the sharp absorption edges of perovskite materials, and the optimized photodetectors exhibit suppressed dark current of 1.85 × 10 − 5 mA cm − 2 , high specific detectivity of 1.37 × 10 12 Jones (cm Hz1/2 W−1). Furthermore, the spectral response can be tuned via managing the bandgap of the perovskite material, and a series of narrowband photodetectors with response spectral range between 680 nm and 710 nm were fabricated. This provides a new design paradigm for a narrowband photodetector with many imaging applications.

Converting a Common Low-Cost Document Scanner into a Multispectral Scanner.

Forged documents and counterfeit currency can be better detected with multispectral imaging in multiple color channels instead of the usual red, green and blue. However, multispectral cameras/scanners are expensive. We propose the construction of a low cost scanner designed to capture multispectral images of documents. A standard sheet-feed scanner was modified by disconnecting its internal light source and connecting an external multispectral light source comprising of narrow band light emitting diodes (LED). A document was scanned by illuminating the scanner light guide successively with different LEDs and capturing a scan of the document. The system costs less than a hundred dollars and is portable. It can potentially be used for applications in verification of questioned documents, checks, receipts and bank notes.

Influence of light source on the strain sensitivity of a polarisation maintaining fibre loop mirror based on voltage demodulation

The sensitivity is an important performance for a polarisation maintaining fibre (PMF) loop mirror (PM-FLM) sensor based on voltage demodulation. This paper investigates the method of improving the strain sensitivity of a PM-FLM based on voltage demodulation, including the demodulation principle, the derivation of the output light power equation, and experimentally studies on the strain sensitivity of a PM-FLM with different narrow-band input light source. The results show that the PM-FLM using a high-power light source as input has a high strain sensitivity but a small linear range of strain measurement, and the PM-FLM using a low-power light source as input has a low strain sensitivity but a large linear range of strain measurement. Hence, a high-power narrow-band light source as input can be chosen to improve the strain sensitivity, and the authors can also reduce the input light source power to enlarge the linear range of strain measurement.

The Protective Effects of Blue Light-Blocking Films With Different Shielding Rates: A Rat Model Study.

PurposeTo examine light emitting diode (LED)-induced retinal photochemical damage and assess the protective performance of blue light-shielding films with different shielding rates in Sprague-Dawley rats (SD rats).MethodsSD rats were randomly divided into five groups: blank control (group I), white LED illumination (group II), and white LED illumination combined with shielding of blue light of wavelength 440 nm at 40%, 60%, and 80% (groups III, IV, and V). The illumination was 200 lux. All animals underwent electroretinography (ERG), hematoxylin-eosin (H&E) staining, immunohistochemical (IHC) staining, and transmission electron microscopy (TEM) observation after 14 days of dark-adaptation before illumination, after 14 days of cyclic illumination, and after 14 days of darkness for recovery following illumination.ResultsERG showed retinal functional loss after LED light exposure. However, retinal cell function was partly recovered after a further 2 weeks of dark adaptation. H&E staining and TEM revealed increases in photoreceptor cell death after illumination. IHC staining demonstrated that oxidative stress was associated with retinal injury. Although retinal light injury was discovered in the LED light-exposure groups, shielding 60% of blue light of wavelength 440 nm (bandwidth 20 nm) protected retinas.ConclusionsCyclic illumination of low light intensity (200 lux) for 14 days produced retinal degeneration; shielding 60% of blue light may protect retinas from light damage.Translational RelevanceThis study found the effective shielding rate that could protect retinas from light damage when shielding specific narrow-band harmful blue light; thus providing a more normative method for protecting eyes from blue light hazard.