Narrow-band Light Research Articles

Photodamage prediction model and optimal lighting system for polychrome artworks in museum

When lighting polychrome artworks in museum, the light sources are required not only to provide high-quality visual performance, but also to minimize the photodamage. Currently, though there are mature methods to calculate visual performance, how to predict the degree of photodamage remains a challenge, which leads to a lack of light sources satisfying both visual and protection requirements. Our study conducted a series of 294 accelerated aging experiments spanning over 11 years for materials commonly used in Chinese polychrome artworks, using isoenergetic white-light D55 and 10 different wavelengths of narrow-band light as experimental light sources. The mathematical model predicting the photodamage degree caused by intensity (I), exposure time (t), the relative spectral power distribution of the light source (S(λ)), and the irradiated material's relative spectral responsivity (P(λ)) to polychrome artworks was established, and the mean absolute percentage error of the model, as verified by experiments, was 11.63 %. Combined with the existing visual performance calculation methods, an optimal lighting algorithm that simultaneously meets high-quality visual performance and minimum photodamage was developed, followed by developing a new Spectrally Tunable White LEDs (STWLEDs) lighting system with 10 LED chips. It is found that the STWLEDs can adjust and output the optimal spectra and recommended illuminance according to the characteristics of polychrome artworks, thus realizing lighting with minimum photodamage, meanwhile, satisfying high-quality visual performance. After testing, as well as satisfying the requirements of visual performance, the average photodamage is reduced by 40.95 % with STWLEDs compared with the traditional WLEDs.

Focusing on mixed narrow band stimuli: Implications for mechanisms of accommodation and displays.

The eye has considerable chromatic aberration, meaning that the accommodative demand varies with wavelength. Given this, how does the eye accommodate to light of differing spectral content? Previous work is not conclusive but, in general, the eye focuses in the center of the visible spectrum for broadband light, and it focuses at a distance appropriate for individual wavelengths for narrowband light. For stimuli containing two colors, there are also mixed reports. This is the second of a series of two papers where we investigate accommodation in relation to chromatic aberrationFernandez-Alonso, Finch, Love, and Read (2024). In this paper, for the first time, we measure how the eye accommodates to images containing two narrowband wavelengths, with varying relative luminance under monocular conditions. We find that the eye tends to accommodate between the two extremes, weighted by the relative luminance. At first sight, this seems reasonable, but we show that image quality would be maximized if the eye instead accommodated on the more luminous wavelength. Next we explore several hypotheses as to what signal the eye might be using to drive accommodation and compare these with the experimental data. We show that the data is best explained if the eye seeks to maximize contrast at low spatial frequencies. We consider the implication of these results for both the mechanism behind accommodation, and for modern displays containing narrowband illuminants.

Practical utility of linked color imaging in colonoscopy: Updated literature review.

The remarkable recent developments in image-enhanced endoscopy (IEE) have significantly contributed to the advancement of diagnostic techniques. Linked color imaging (LCI) is an IEE technique in which color differences are expanded by processing image data to enhance short-wavelength narrow-band light. This feature of LCI causes reddish areas to appear redder and whitish areas to appear whiter. Because most colorectal lesions, such as neoplastic and inflammatory lesions, have a reddish tone, LCI is an effective tool for identifying colorectal lesions by clarifying the redder areas and distinguishing them from the surrounding normal mucosa. To date, eight randomized controlled trials have been conducted to evaluate the effectiveness of LCI in identifying colorectal adenomatous lesions. The results of a meta-analysis integrating these studies demonstrated that LCI was superior to white-light endoscopy for detecting colorectal adenomatous lesions. LCI also improves the detection of serrated lesions by enhancing their whiteness. Furthermore, accumulating evidence suggests that LCI is superior to white-light endoscopy for the diagnosis of the colonic mucosa in patients with ulcerative colitis. In this review, based on a comprehensive search of the current literature since the implementation of LCI, the utility of LCI in the detection and diagnosis of colorectal lesions is discussed. Additionally, the latest data, including attempts to combine artificial intelligence and LCI, are presented.

Tunable Narrowband to Wideband emission of Mn2+, Eu2+ Co-doped GdMgAl11O19 for multifunctional applications

As the widespread application of white light-emitting diodes (WLEDs) in lighting field and liquid crystal display (LCD) backlight, the development of phosphors toward multifunctional applications is considered to be an inevitable tendency. In this work, multi-color light emissions have been realized in Eu2+ and Mn2+-activated magnetoplumbite-type GdMgAl11O19 (GMAO) along with adjustable photoluminescence properties. Significantly, a promising narrow-band green light emission can be achieved by Mn2+-activated GMAO with the full width at half maximum (FWHM) of 27 nm, and such narrow emission band makes the as-prepared WLED device reach 121 % of National Television Standards Committee (NTSC), which can act as an ideal LCD backlight. On the other hand, the broad cyan light can be achieved in Eu2+-activated GMAO. Moreover, multi-color light emissions have been realized in Eu2+ and Mn2+ co-doped GMAO, and the energy transfer from Eu2+ to Mn2+ ions was established. Benefitting from the broad band cyan light emission of Eu2+ ion, a promising WLED device with high color rendering index (CRI) of 90 has been fabricated by using Eu2+ and Mn2+ co-doped sample. The result indicates the multifunctional applications of the GMAO modulated by Eu2+ and Mn2+ activators.

Enhancing the pure water splitting using carbon-iron oxide–carbon nitride (Fe2O3-C/CN) heterostructure

Highly efficient pure photocatalysts for water-splitting applications have long been plagued by structure imperfectness, narrowband light absorption, rapid charge recombination, and sluggish surface reaction kinetics. Herein we report a Z-scheme heterojunction photocatalyst made of Fe2O3, CN, and a conductive carbon layer (C) at the interface of the two materials (Fe2O3-C/CN). The structure has been characterized using a range of physicochemical and photo-electrochemical techniques. Compared to pristine Fe2O3, the Fe2O3-C/CN photocatalyst revealed superior photogenerated charge carriers, transport efficiency, and suppressed recombination process along with the conductive carbon layer acting as a mediator. The optimum composite of (5 wt% Fe2O3-C/CN) shows excellent activity towards pure water splitting, which reached 408 and 199 μmol/g.h for H2 and O2 evolution respectively, and a solar-to-hydrogen conversion efficiency of approximately 0.29 % when used for the pure water splitting process. Such a superior efficiency and production rate offer great potential for pure water splitting, and provide an alternative solution to future green energy production processes.

Mid-infrared tunable filter based on a femtosecond-written silica volume Bragg grating.

A silica volume Bragg grating (VBG) is used to filter the light of a mid-infrared (mid-IR) supercontinuum laser. The VBG with a 7 µm period was inscribed with 800 nm pulses with a 100 fs duration and the phase-mask technique over a glass thickness of 3 mm. Despite silica's absorption, the VBG allows obtaining a narrowband light source tunable from 2.9 to 4.2 µm with a full width at half maximum (FWHM) of 29 nm. This demonstrates the great potential of using femtosecond-written VBGs as highly tunable, yet selective, spectral filters in the mid-IR.

Two‐dimensionalization of 3D perovskites for passive narrowband Photodetection

AbstractIn the rapidly advancing field of information technology, passive sensors with the exemption of external power input can serve as intelligent instruments for end‐node data acquisition. 3D perovskites have been recognized as a superior optoelectronic material but suffering from notorious instability due to their “soft lattice” nature. Replacing by their 2D counterparts in these photo‐sensing applications can boost the reliability level. However, traditional fabrication for 2D perovskite relay on wet chemistry methods, exhibiting complication, and inefficiency in making high‐quality films for device integration. This study unveils a new solid–solid conversion routing toward a direct transformation from 3D orientated films into 2D highly crystalline configuration, based on a spontaneous lattice regulation mechanism through an amine steam treatment. The resultant 2D film exhibits greater orientational micromorphology and a distinct monochromatic narrowband light sensing behavior after integration into a self‐powered photodetector. This method on perovskite conversion bears the promise of advanced future‐manufacturing for high‐performance photonic sensing.image

Improving the performance of speckle correlation imaging by using a speckle refinement method with self-calibrated homomorphic filtering

Scattering imaging based on speckle correlation is an attractive topic as it enables the rapid reconstruction of the object image through computational methods in a compact setup. However, this method typically relies on high-contrast speckle images obtained under narrowband light illumination in a darkroom environment, limiting its application scenarios. Here, we demonstrate a self-calibrated homomorphic filtering (SCHF) method that significantly enhances speckle contrast by modifying the distribution of components within the speckle image, thereby improving imaging performance. The experimental results reveal that our method leverages the physical mechanism of speckle correlation to obtain the optimal filtering solution under the guidance of a self-calibrated strategy. The integration of this method with current mainstream speckle correlation techniques showcases its scalability. Even in scenarios under ambient light interference or broadband light illumination, the SCHF is effective in improving imaging performance, demonstrating its practical application potential.

Tunable and narrowband shortwave infrared light sensing enabled by dual-Fano resonance enhanced sum-frequency generation

Tunable and narrowband light detection provides a means of selectively detecting optical signals at a specific wavelength, enabling a precise tool for object identification, machine vision, spectroscopy, and so on. Simultaneous tunable and narrowband response in shortwave infrared (SWIR) detectors is critical yet still challenging. This work utilizes dual-Fano resonance enhanced sum-frequency generation in a two-layer structure comprising a silicon metasurface and a two-dimensional (2D) nonlinear GaSe layer to realize tunable and narrowband light detection in the SWIR range. The silicon metasurface affords a high-quality-factor dual-Fano resonance in the SWIR regime, which enhances the near-field optical density of the two resonant wavelengths (pump and signal) when passing through the 2D nonlinear layer, leading to drastically enhanced sum-frequency generation. The sum-frequency light at a visible wavelength that contains the information of the SWIR signal light, can then be detected by a low-noise visible detector. The tunability and selectivity in the response spectrum stem from the geometry-dependent dual-Fano resonance in the silicon metasurface, covering the 1200–1550 nm range. The upconversion detector exhibits a sub-nanometer narrowband detection with a full width at half maximum of down to ∼0.1 nm, owing to the high quality factor of the Fano resonances. This SWIR narrowband detection is one of the best performances reported so far, much narrower than commercial filter products. The peak value of the specific detectivity of 1.5 × 1012 Jones at 1256.3 nm is achieved, comparable to broadband commercial InGaAs detectors. The detector designs in this work open up the opportunity of upconversion sensors for delicate spectroscopic applications.

Enhancing antithermal-quenching properties of terbium-doped phosphors through Nb/Ta substitution: Insights into the role of intervalence charge transfer and excitation-driven modulation

Currently, the unique 5D4 energy level of terbium (Tb3+) can contribute to narrow-band green light emission, which has high application prospects. However, due to its poor thermal stability at high temperatures, how to enhance the antithermal-quenching properties of Tb-doped phosphors has become a research difficulty in the field of solid-state lighting and temperature sensing. In this contribution, the antithermal-quenching green-emitting of terbium was achieved by Nb/Ta substitution to form GdNb1-xTaxO4:Tb3+ phosphors with various components. Photoluminescence analyses reveal an increasing trend in both the optical band gap and the intervalence charge transfer (IVCT) energy level positions with substitution. Variable-temperature spectrums observed that the phosphors under different compositions presented a large discrepancy in thermal quenching performance. It is elucidated that the elevated position of the IVCT energy level (IVCT-EL) predominantly influences thermal quenching, bolstering its role as a compensatory luminescence channel of 5D3→5D4 far more than functioning as a quenching luminescence channel for Tb3+5D3/5D4. Delving into the perspective of IVCT-EL positioning unveils the intrinsic mechanism through which IVCT-EL positions modulate the thermal quenching properties of phosphors with varying compositions due to the substitution of Ta for Nb. This insight facilitates the realization of enhanced thermal quenching resistance in phosphors. Furthermore, the antithermal-quenching property of Tb3+ in single-phase phosphors can be effectively modulated by excitation at different wavelengths. This tuning scheme not only advances the exploration of terbium-doped antithermal-quenching phosphors but also provides a novel strategy and reference for designing green-emitting phosphors in the fields of lighting and sensing.

Influence of Aberration-Free, Narrowband Light on the Choroidal Thickness and Eye Length.

To determine whether light chromaticity without defocus induced by longitudinal chromatic aberration (LCA) is sufficient to regulate eye growth. An interferometric setup based on a spatial light modulator was used to illuminate the dominant eyes of 23 participants for 30minutes with three aberration-free stimulation conditions: (1) short wavelength (450nm), (2) long wavelength (638nm), and (3) broadband light (450-700nm), covering a retinal area of 12°. The non-dominant eye was occluded and remained as the control eye. Axial length and choroidal thickness were measured before and after the illumination period. Axial length increased significantly from baseline for short-wavelength (P < 0.01, 7.4 ± 2.2 µm) and long-wavelength (P = 0.01, 4.8 ± 1.7 µm) light. The broadband condition also showed an increase in axial length with no significance (P = 0.08, 5.1 ± 3.5 µm). The choroidal thickness significantly decreased in the case of long-wavelength light (P < 0.01, -5.7 ± 2.2 µm), but there was no significant change after short-wavelength and broadband illumination. The axial length and choroidal thickness did not differ significantly between the test and control eyes or between the illumination conditions (all P > 0.05). Also, the illuminated versus non-illuminated choroidal zone did not show a significant difference (all P > 0.05). All stimulation conditions with short- and long-wavelength light and broadband light led to axial elongation and choroidal thinning. Therefore, light chromaticity without defocus induced by LCA is suggested to be insufficient to regulate eye growth. This study helps in understanding if light chromaticity alone is a sufficient regulator of eye growth.

Chiral quasi bound states in the continuum for augmented reality

Augmented Reality technology enables users to interact with virtual imagines and the real world. The emergence of AR has propelled the development of the next generation of optical devices towards miniaturization, lightweight design, and enhanced light field manipulation capabilities. However, current AR glass still suffer from shortcomings of low efficiency. This work proposes a near-eye display device based on bilayer chiral quasi-BIC (Bound States in the continuum) nonlocal metasurfaces which can reflect narrow bandwidth RGB light with high efficiency while being able to see the natural environment clearly. At the same time, the geometric phase is introduced to realize oblique emission and reflective focusing. Due to its ability to manipulate narrowband light fields, it can reduce the interaction of metasurfaces and environment light, and has potential applications in the fields of imaging and near-eye display.

Weak Faraday Effect Measurement in Anti-Resonant Fiber Based on Intermodal Interference Suppression

Anti-resonant fiber (ARF) works well in a relatively strong magnetic field due to its weak Faraday effect, which results from the fundamental mode mainly transmitting in the air core. Accurately measuring the Faraday effect strength, i.e., the effective Verdet constant, of an ARF determines its applicable scenarios. However, the effective Verdet constant of ARF is ~3 orders of magnitude lower than that of a standard single-mode fiber, which is very difficult to measure. In this paper, we reveal that intermodal interference is the main obstacle to measuring the ultralow effective Verdet constant of ARF and propose using a narrow-band low-coherence light to suppress it. The measured effective Verdet constant of ARF is 0.423 ± 0.005 mrad/T/m at 1550 nm.

Effects of short-term exposure to red or near-infrared light on axial length in young human subjects.

To determine whether visible light is needed to elicit axial eye shortening by exposure to long wavelength light. Incoherent narrow-band red (620 ± 10 nm) or near-infrared (NIR, 875 ± 30 nm) light was generated by an array of light-emitting diodes (LEDs) and projected monocularly in 17 myopic and 13 non-myopic subjects for 10 min. The fellow eye was occluded. Light sources were positioned 50 cm from the eye in a dark room. Axial length (AL) was measured before and after the exposure using low-coherence interferometry. Non-myopic subjects responded to red light with significant eye shortening, while NIR light induced minor axial elongation (-13.3 ± 17.3 μm vs. +6.5 ± 11.6 μm, respectively, p = 0.005). Only 41% of the myopic subjects responded to red light exposure with a decrease in AL and changes were therefore, on average, not significantly different from those observed with NIR light (+0.2 ± 12.1 μm vs. +1.1 ± 11.2 μm, respectively, p = 0.83). Interestingly, there was a significant correlation between refractive error and induced changes in AL after exposure to NIR light in myopic eyes (r(15) = -0.52, p = 0.03) and induced changes in AL after exposure to red light in non-myopic eyes (r(11) = 0.62, p = 0.02), with more induced axial elongation with increasing refractive error. Incoherent narrow-band red light at 620 nm induced axial shortening in 77% of non-myopic and 41% of myopic eyes. NIR light did not induce any significant changes in AL in either refractive group, suggesting that the beneficial effect of red laser light therapy on myopia progression requires visible stimulation and not simply thermal energy.

Degree of polarization in dissipative optical systems

The polarization matrix formalism is employed to analyze the polarization properties of transmitted narrowband light through several optical setups involving active and dissipative structures. It is demonstrated that the degree of polarization of the output light can increase after propagation in a active/dissipative periodic media. Furthermore, the impact of introducing optical elements like polarizers, compensators, and rotators is examined, and their collective effect on the degree of polarization is discussed.

Diagnostic performance of blue laser imaging for early detection of gastric cancer: A systematic review and meta-analysis.

Gastric cancer (GC) is associated with a significant global health burden and high mortality rates when diagnosed at later stages. The diagnosis often occurs at advanced stages when treatment options are limited and less effective. Early detection strategies are crucial to improving survival rates and outcomes for patients. Blue laser imaging (BLI) is an image-enhanced endoscopy technique that utilizes white light and narrow-band light to detect pathological changes in the mucosal architecture. This study aims at investigating the diagnostic performance of BLI for the detection of GC. A comprehensive search was conducted across multiple databases from inception until March 2023. Studies assessing the diagnostic efficacy of BLI for GC detection were included. The sensitivity, specificity and accuracy of BLI were calculated using pooled proportions and 95% confidence intervals (CI) with a random-effects model. Heterogeneity among the included studies was assessed using the I2 statistic. Six studies were included in the pooled analysis. There were 708 patients with 380 GC lesions. Most of the lesions involved the lower two-thirds of the stomach. The pooled performance metrics of BLI for GC detection were as follows: sensitivity of 91.9% (95% CI 83.3-96.3%; I2 = 82.3%), specificity of 93.4% (95% CI 82.0-97.8%; I2 = 87.9%) and accuracy of 95.4% (95% CI 72.6-99.8%; I2 = 73.6%). BLI demonstrates high diagnostic efficacy for the detection of GC. BLI can be a valuable tool in clinical practice. However, large-scale, randomized controlled studies are needed to further establish the role of BLI in routine clinical practice for GC detection.

Ocular accommodation and wavelength: The effect of longitudinal chromatic aberration on the stimulus-response curve.

The longitudinal chromatic aberration (LCA) of the eye creates a chromatic blur on the retina that is an important cue for accommodation. Although this mechanism can work optimally in broadband illuminants such as daylight, it is not clear how the system responds to the narrowband illuminants used by many modern displays. Here, we measured pupil and accommodative responses as well as visual acuity under narrowband light-emitting diode (LED) illuminants of different peak wavelengths. Observers were able to accommodate under narrowband light and compensate for the LCA of the eye, with no difference in the variability of the steady-state accommodation response between narrowband and broadband illuminants. Intriguingly, our subjects compensated more fully for LCA at nearer distances. That is, the difference in accommodation to different wavelengths became larger when the object was placed nearer the observer, causing the slope of the accommodation response curve to become shallower for shorter wavelengths and steeper for longer ones. Within the accommodative range of observers, accommodative errors were small and visual acuity normal. When comparing between illuminants, when accommodation was accurate, visual acuity was worst for blue narrowband light. This cannot be due to the sparser spacing for S-cones, as our stimuli had equal luminance and thus activated LM-cones roughly equally. It is likely because ocular LCA changes more rapidly at shorter wavelength and so the finite spectral bandwidth of LEDs corresponds to a greater dioptric range at shorter wavelengths. This effect disappears for larger accommodative errors, due to the increased depth of focus of the eye.

Design of Multifunctional Color Routers with Kerker Switching Using Generative Adversarial Networks

AbstractTo achieve optoelectronic devices with high resolution and efficiency, there is a pressing need for optical structural units that possess an ultrasmall footprint yet exhibit strong controllability in both the frequency and spatial domains. For dielectric nanoparticles, the overlap of electric and magnetic dipole moments can scatter light completely forward or backward, which is called Kerker theory. This effect can expand to any multipoles and any directions, re‐named as generalized Kerker effect, and realize controllable light manipulation at full space and full spectrum using well‐designed dielectric structures. However, the complex situations of multipole couplings make it difficult to achieve structural design. Here, generative artificial intelligence (AI) is utilized to facilitate multi‐objective‐oriented structural design, wherein the study leverages the concept of “combined spectra” that consider both spectra and direction ratios as labels. The proposed generative adversarial network (GAN) is named as DDGAN (double‐discriminator GAN) that discriminates both images and spectral labels. Using trained networks, the simultaneous design for scattering color and directivities, RGB color routers, as well as narrowband light routers is achieved. Notably, all generated structures possess a footprint &lt;600 × 600 nm indicating their potential applications in optoelectronic devices with ultrahigh resolution.

Influence of Light of Different Narrowband Light on the Key of Calvin Cycle and Antioxidant Enzyme, Secondary Metabolites and Microbial Communities in Soybeans

Influence of Light of Different Narrowband Light on the Key of Calvin Cycle and Antioxidant Enzyme, Secondary Metabolites and Microbial Communities in Soybeans

Expert consensus on the clinical application of narrow-band intense pulsed light (2024 edition)

The continuous innovation of medical cosmetology technology promotes the rapid development of aesthetic medicine. Narrow-band intense pulsed light (NB-IPL), which is developed based on conventional intense pulsed light, is a more accurate, efficient, and safer technique on clinical application. In order to promote more professionalization and standardization of the clinical application of NB-IPL, a panel of clinical experts in plastic surgery, dermatology and other fields developed the consensus based on the evidence-based medicine, clinical practice, and authoritative guidelines of other disciplines. The consensus panel discussed the indications, treatment parameters, contraindications, and precautions for the clinical application of NB-IPL and would serve as a reference for clinicians, nurses, teaching and research personnels engaged in plastic and cosmetics related work.