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Photothermal materials with broadband optical absorption and high conversion efficiency are intensively pursued to date. Here, proposing by the d-d interband transitions, we report an unprecedented high-entropy alloy FeCoNiTiVCrCu nanoparticles that the energy regions below and above the Fermi level (±4 eV) have been fully filled by the 3 d transition metals, which realizes an average absorbance greater than 96% in the entire solar spectrum (wavelength of 250 to 2500 nm). Furthermore, we also calculated the photothermal conversion efficiency and the evaporation rate towards the steam generation. Due to its pronounced full light capture and ultrafast local heating, our high-entropy-alloy nanoparticle-based solar steam generator has over 98% efficiency under one sun irradiation, meanwhile enabling a high evaporation rate of 2.26 kg m -2 h -1 .

Louise Finlayson acknowledges financial support from EPSRC Industrial Doctorate Centre Scheme (2262922) and the Laser Research and Therapy Fund (registered charity SC030850). An increase in the use of light-based technology and medical devices has created a demand for informative and accessible data showing the depth that light penetrates into skin and how this varies with wavelength. These data would be particularly beneficial in many areas of medical research and would support the use and development of disease-targeted light-based therapies for specific skin diseases, based on increased understanding of wavelength-dependency of cutaneous penetration effects. We have used Monte Carlo radiative transport (MCRT) to simulate light propagation through a multi-layered skin model for the wavelength range of 200 nm – 1000 nm. We further adapted the simulation to compare the effect of direct and diffuse light sources, varying incident angles and stratum corneum thickness. The lateral spread of light in skin was also investigated. As anticipated, we found that the penetration depth of light into skin varies with wavelength in accordance with the optical properties of skin. Penetration depth of ultraviolet radiation was also increased when the stratum corneum was thinner. These observations enhance understanding of the wavelength-dependency and characteristics of light penetration of skin, which has potential for clinical impact regarding optimizing light-based diagnostic and therapeutic approaches for skin disease. Publisher PDF

Oxide crystals have been widely used in the nonlinear optical (NLO) field in the ultraviolet-visible and near-infrared region. Most of the traditional oxide crystals are restricted in the mid-infrared region due to their narrow transmission window. Hence, attempting to extend infrared cutoff wavelength of oxide has attracted much attention. In our work, we reported two new tellurate Li 2 TiTeO 6 (LTT) and Li 2 SnTeO 6 - (LST) with broad transparent region 0.38-6.72 and 0.38-6.86 μm, respectively, which could be excellent candidates for the mid-infrared NLO application. Both LTT and LST are crystallized in the orthorhombic space group P nn 2. The LTT crystal exhibits intense powder second-order generation efficiency (26×KDP) under the fundamental wavelength of 1064 nm. The first-principles calculations and dipole moments were used to illustrate the results of the powder second-harmonic generations based on the crystal structures. Our results provide a novel oxide NLO crystal with a strong SHG and wide transparency range. It also paves a way to design new oxide mid-IR NLO crystals.

In this paper we investigate combinatorial constructions for $w$-cyclic holely group divisible packings with block size three (briefly by $3$-HGDPs). For any positive integers $u,v,w$ with $u\equiv0,1~(\bmod~3)$, the exact number of base blocks of a maximum $w$-cyclic $3$-HGDP of type $(u,w^v)$ is determined. This result is used to determine the exact number of codewords in a maximum three-dimensional $(u\times v\times w,3,1)$ optical orthogonal code with at most one optical pulse per spatial plane and per wavelength plane.

All‐optical cross‐connects need to perform switching not only in the space domain, but also in the wavelength domain. Switching in the wavelength domain requires wavelength converters (WCs), and WCs capable of simultaneously performing multiple wavelength conversions have been invented. We can use multiple stages of such WCs to form a wavelength exchange network to allow an even larger number of simultaneous wavelength conversions. However, WCs with a full conversion range are often difficult to implement. In the paper, we develop new techniques and theories that can reduce the conversion range requirement and still maintain the full connectivity of all‐optical space/wavelength switches.

Purpose: In vivo MR elastography (MRE) holds promise as a neuroimaging marker. In cerebral MRE, shear waves are introduced into the brain, which also stimulate vibrations in adjacent CSF, resulting in blurring and biased stiffness values near brain surfaces. We here propose inversion-recovery MRE (IR-MRE) to suppress CSF signal and improve stiffness quantification in brain surface areas. Methods: Inversion-recovery MRE was demonstrated in agar-based phantoms with solid-fluid interfaces and 11 healthy volunteers using 31.25-Hz harmonic vibrations. It was performed by standard single-shot, spin-echo EPI MRE following 2800-ms IR preparation. Wave fields were acquired in 10 axial slices and analyzed for shear wave speed (SWS) as a surrogate marker of tissue stiffness by wavenumber-based multicomponent inversion. Results: Phantom SWS values near fluid interfaces were 7.5 ± 3.0% higher in IR-MRE than MRE (P = .01). In the brain, IR-MRE SNR was 17% lower than in MRE, without influencing parenchymal SWS (MRE: 1.38 ± 0.02 m/s; IR-MRE: 1.39 ± 0.03 m/s; P = .18). The IR-MRE tissue-CSF interfaces appeared sharper, showing 10% higher SWS near brain surfaces (MRE: 1.01 ± 0.03 m/s; IR-MRE: 1.11 ± 0.01 m/s; P < .001) and 39% smaller ventricle sizes than MRE (P < .001). Conclusions: Our results show that brain MRE is affected by fluid oscillations that can be suppressed by IR-MRE, which improves the depiction of anatomy in stiffness maps and the quantification of stiffness values in brain surface areas. Moreover, we measured similar stiffness values in brain parenchyma with and without fluid suppression, which indicates that shear wavelengths in solid and fluid compartments are identical, consistent with the theory of biphasic poroelastic media.

This study is focused on comparing the effect of various energy densities and wavelengths of diode lasers on the proliferation of human gingival fibroblast (HGF) cells in vitro. In this study, 204 sample cells were examined in 4 test groups (laser radiation) and 1 control group (non-laser radiation). The proliferation rate of radiated cells with wavelengths of 635, 660, 808 and 980 nm and the densities of 1, 1.5, 2.5 and 4 J cm-2 was measured after 1, 3 and 5 days using the MTT assay. The proliferation rate of human gingival fibroblast (HGF) cells in test groups was increased on day 1 at wavelengths of 635, 808 and 980 nm and on day 3 at the wavelength of 980 nm compared with the control group. Our findings denoted that the photobiomodulation therapy increased the proliferation rate of HGF. The most desirable laser radiation setting, which led to the highest proliferation rate of the cells, included 980 nm wavelength with 1, 1.5 and 4 J cm-2 energy densities and 635 nm wavelength with 4 J cm-2 energy density.

The generated light can be tuned to cover almost the entire spectral range from deep-ultraviolet to terahertz wavelengths by utilizing the nonlinear optical crystals with a simple frequency doubling process. Among them, the discovery of novel candidates for the production of deep-ultraviolet light is by extension a great challenge toward realizing the vast potential. Actually, the availability for this process mainly depends on whether the critical performance can be well coexisted in one practical crystal. Herein, the first magnesium fluorooxoborate MgB5 O7 F3 was synthesized as a new competitive candidate for deep-ultraviolet nonlinear optical application. It has a sufficiently large nonlinearity and a deep-ultraviolet phase matching wavelength, indicating that it holds great potential for the production of coherent light below 200 nm. The critical performance enhancement of MgB5 O7 F3 when compared with its isomorphic phases was demonstrated and discussed. More importantly, we proposed that fluorooxoborate system with the general formula of MB5 O7 F3 (M=divalent metal) possesses stable fluorine terminated framework, which makes them tend to retain their crystallized space groups unchanged.

Based on previous reports on the optical microscopy contrast of mechanically exfoliated few layer CrCl 3 transferred on 285 nm and 270 nm SiO 2 on Si(100), we focus on the experimental determination of an effective mean complex refractive index via a fitting analysis based on the Fresnel equations formalism. Accordingly, the layer and wavelength-dependent absorbance and reflectance are calculated. Layer and wavelength-dependent optical contrast curves are then evaluated demonstrating that the contrast is significantly high only around well-defined wavelength bands. This is validated a posteriori, by experimental UV-Vis absorbance data. The present study aims to show the way towards the most reliable determination of thickness of the 2D material flakes during exfoliation.

This chapter presents an overview of millimeter‐wave antennas and important related issues. In particular, the unique properties of millimeter‐wave propagation are addressed first. With a shorter wavelength, the millimeter‐waves suffer from higher pathloss and worse diffraction in its propagation compared with microwaves. The wavelength of the order of millimeter determines the difference of applications of millimeter‐wave wireless systems from the systems operating at lower or higher frequencies. Also, the design of antennas at this band has its own special considerations from the selection of types, feeding structures, materials, fabrication, and testing. In addition to the fast‐developing applications, this chapter updates the latest development of applications of millimeter‐wave technology in the 5G and future wireless communication networks as well.

This study presents the concept of an economic in situ light-scattering sensor for real-time measurement of the solid content in tailings facilities. An experimental setup using a blue (405 nm wavelength) laser diode and silicon photodiodes was constructed to measure the angular distribution of the intensity of scattered light. It was found that the angular intensity of scattered light for tailing samples follows a cosn (θ) relation with n ≈ 1.5, where θ is the angle between the laser beam and the photodiode. An angular value of θ = 20° was chosen for the sensor design based on a high signal-to-noise ratio. The setup was used to determine the relation between scattered light intensity and solids content using a thickened tailings underflow from an oil sands facility and Kaolin as a model material. It was observed that the intensity of scattered light tends to increase with an increase in solids content, with qualitatively similar settling behavior for the two materials but at largely different time scales. An insertion-based prototype was built and tested in a large (2.7 m height) settling column with treated mature fine tailings, and the light-scattering data were verified by standard gravimetric method and gamma-ray measurements. In general, good agreement was established between these measurements in the absence of optical fouling, which demonstrates the potential of the sensor as an effective tool for tailings management.

A series of Mg21 Ca4 Na4 (PO4 )18 :Eu2+ -Eu3+ phosphors was successfully synthesized using a high-temperature solid-state method in an air atmosphere. The phase structures and luminescence properties of the samples were studied in detail. The phosphors exhibited strong visible light emission under different wavelengths of ultraviolet light excitation. By harmonizing the doping concentration of Eu3+ to adjust the relative luminescence intensity of Eu2+ and Eu3+ , a colourful emission of phosphors could be achieved. In addition, the colour coordinates of the International Commission on lighting indicated that Mg21 Ca4 Na4 (PO)18 :Eu2+ -Eu3+ could be considered as a potential blue, orange and red phosphor for white light-emitting diode applications.

A photonic crystal ring resonator‐based 6 × 6 router has been designed and reported. The router is designed using silicon pillars with a refractive index of 3.47 perforated in the air background of refractive index 1 in a square lattice with a lattice constant of a = 562 nm. The router is designed to operate in the third optical window wavelength which has low loss and most widely used in optical communication systems and networks. Plane‐wave expansion and finite difference time domain method has been used to obtain the bandgap and performance of the designed router, which exhibits acceptable performance such as low insertion loss, low propagation delay, and low crosstalk. These routers will find applications in the photonic integrated circuit that paves a path to all‐optical networks.

In this paper, the uncertainty budget from 10 sources we claim they have direct impact on measurement is estimated. The measurement has been applied to nominal step heights of 1.34 and 1.50 μm using a dual-wavelength Twyman-Green interferometer. Experimental results show that the measured step heights match with their nominal values with expanded uncertainty in the range of 5% from the object being measured. The performance of the measurement process over time has been estimated at different confidence levels and the obtained results show that the process is maintained in a state of statistical control. To the best of our knowledge, this is the first report for estimation of uncertainty budget from a synthetic wavelength.

Objective A mobile handheld snapshot hyperspectral imaging device was developed and tested for in vivo skin evaluation using a new spectral imaging technology. Methods The device is equipped with four different LED light sources (VIS, 810 nm, 850 nm, and 940 nm) for illumination. Based on a diffractive optical element (DOE) combined with a CMOS sensor chip, a snapshot hyperspectral imager is achieved for the application on human skin. The diffractive optical element (DOE) consists of a two‐dimensional array of identically repeated diffractive microstructures. One hyperspectral image for all wavelength regions is taken within a few seconds. Complex recalculation of the VIS spectral distribution and image information from the received DOE image requires several minutes, depending on computing performance. A risk assessment on the irradiation sources shows no risk of harm due to the LED radiation. Results Skin tone color patches experiments reproducibly deliver images and spectra of different skin tones. First in vivo use of the device identified pigmentation changes within the field of view. Conclusion We present a working mobile snapshot hyperspectral imaging tool based on diffractive optical elements. This device or future developments thereof can be used for broad skin evaluation in vivo.

Commercially used inorganic phosphors heavily depend on lanthanide doped host materials which are becoming more expensive and also their availability is limited due to scarcity. In this regard, a new lanthanide-free self-activated full-color emission phosphor in Y3+ doped Sr3 Bi(VO4 )3 system was developed by the conventional ceramic route. These phosphors crystallize into a hexagonal-type palmierite mineral structure. They exhibit broad excitation bands in the wavelength region of 250-400 nm, owing to the charge transfer transitions from both O2- and Bi6s2 electrons to V5+ . Upon excitation, these phosphors show bright broad emissions in the 400-750 nm wavelength range, peaking around 535 nm, with a large full width half maximum of 160 nm. The Y substitution allows tuning of the emission from yellowish green to bluish white due to increased distortion of [VO4 ]3- tetrahedron. Consequently, the CIE color coordinates changed from (0.42, 0.50) to (0.31, 0.35) which lies in the near-white region in the chromaticity diagram. Thus, the newly developed Y doped Sr3 Bi(VO4 )3 is a promising lanthanide-free full-color emission phosphor for applications in pc-white light emitting diodes.

Chemiluminescence imaging is imperative for diagnostics and imaging due to its intrinsically high sensitivity. To improve in vivo detection of biomarkers, chemiluminophores that simultaneously possess near-infrared (NIR) emission and modular structures amenable to construction of activatable probes are highly desired; however, these are rare. Herein, we report two chemiluminophores with record long NIR emission (>750 nm) via integration of dicyanomethylene-4H-benzothiopyran or dicyanomethylene-4H-benzoselenopyran with dioxetane unit. Caging of the chemiluminophores with different cleavable moieties produces NIR chemiluminescence probes (NCPs) that only produce signals upon reaction with reactive oxygen species or enzymes, for example, β-galactosidase, with a tissue-penetration depth of up to 2 cm. Thus, this study provides NIR chemiluminescence molecular scaffolds applicable for in vivo turn-on imaging of versatile biomarkers in deep tissues. Ministry of Education (MOE) Nanyang Technological University This work was supported by Nanyang Technological University (Start-up Grant: M4081627) and Singapore Ministry of Education Academic Research Fund Tier 1 (2019-T1-002-045,RG125/19) and Tier 2 (MOE2018-T2-2-042)

Objective: To estimate the implant surface temperature at titanium dental implants during calibrated irradiation using double wavelength laser. Material and methods: A double wavelength laser, 2780 nm Er,Cr:YSGG and 940 nm diode, was calibrated and used to irradiate pristine titanium dental implants, OsseoSpeed, TiUnite and Roxolid SLActive, representing different surface modifications. Initial calibration (21 implants; 7 implants/group) intended to identify optimal wavelength/specific output power/energy that not critically increased the temperature or altered the micro-texture of the implant surface. Subsequent experimental study (30 implants; 10 implants/group) evaluated implant surface temperature changes over 190 s. Irradiation using a computerized robotic setup. Results: Based on the initial calibration, the following output powers/energies were employed: Er,Cr:YSGG laser 18.4 mJ/pulse (7.3 J/cm2)–36.2 mJ/pulse (14.4 J/cm2) depending on implant surface; diode laser 3.3 W (1321.0 W/cm2). During double wavelength irradiation, implant surface temperatures dropped over the first 20 s from baseline 37°C to mean temperatures ranging between 25.7 and 26.3°C. Differences in mean temperatures between OsseoSpeed and TiUnite implants were statistically significant (p

International audience; Leaf optical properties impact leaf energy balance and thus leaf temperature. The effect of leaf development on mid-infrared (MIR) reflectance, and hence thermal emissivity, has not been investigated in detail. We measured a suite of morphological characteristics, as well as directional-hemispherical reflectance from ultraviolet to thermal infrared wavelengths (250 nm to 20 µm) of leaves from five temperate deciduous tree species over the 8 wk following spring leaf emergence. By contrast to reflectance at shorter wavelengths, the shape and magnitude of MIR reflectance spectra changed markedly with development. MIR spectral differences among species became more pronounced and unique as leaves matured. Comparison of reflectance spectra of intact vs dried and ground leaves points to cuticular developmentand not internal structural or biochemical changesas the main driving factor. Accompanying the observed spectral changes was a drop in thermal emissivity from about 0.99 to 0.95 over the 8 wk following leaf emergence. Emissivity changes were not large enough to substantially influence leaf temperature, but they could potentially lead to a bias in radiometrically measured temperatures of up to 3 K. Our results also pointed to the potential for using MIR spectroscopy to better understand species-level differences in cuticular development and composition.

Purpose In this work a simulation study is performed to gain insights in the patterns of induced radiofrequency (RF) currents for various implant-like structures at 1.5 T. The previously introduced transfer matrix (TM) is used to determine why certain current patterns have a tendency to naturally occur. This can benefit current safety assessment techniques and may enable the identification of critical exposure conditions. Theory and methods The induced current on an elongated implant can be determined by multiplication of the incident electric field along the implant with its TM. The eigenmode spectrum of the TMs for various lengths and various types of implants are determined. The eigenvector with the highest eigenvalue describes the incident electric field pattern that induces the highest current which in turn will lead to highest heating. Subsequently, a statistical probability analysis is performed using a wide range of potential incident electric field distributions in a representative human subject model during a 1.5 T MR exam which are determined by means of electromagnetic FDTD simulations. These incident electric field distributions and the resulting induced current patterns are projected onto eigenvectors of the TM to determine which eigenmodes of the implant dominate the current patterns. Results The eigenvectors of the TM of bare and insulated wires resemble sinusoidal harmonics of a string fixed at both ends similar to the natural-current distribution on thin antennas(1). The currents on implants shorter than 20 cm are generally dominated by the first harmonic (similar to half a sine wave). This is firstly because for these implant lengths (relative to the RF wavelength), the first eigenvalue is more than three times bigger than the second showing the ability of an implant to accommodate one eigenmode better than another. Secondly, the incident electric fields have a high likelihood (≳95,7%) to project predominantly on this first eigenmode. Conclusion The eigenmode spectrum of the TM of an implant provides insight into the expected shape of induced current distributions and worst-case exposure conditions. For short implants, the first eigenvector is dominant. In addition, realistic incident electric field distributions project more heavily on this eigenvector. Both effects together cause significant currents to always resemble the dominant eigenmode of the TM for short implants at 1.5 T.

In the present study, CaZrO3 nanophosphors were sensitized with lanthanum (La) at different concentrations (0.5, 1.0, 1.5, 2.0, and 2.5) prepared using polyvinyl alcohol as the chelating agent through the sol-gel method. To study their structural and optical properties, samples were characterized by X-ray diffractometry (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence (PL). The XRD results revealed that samples were well crystallized and average crystallite sizes were calculated. The average crystallite size value was in good agreement with the value obtained from TEM analysis. Energy dispersive spectroscopy and FE-SEM confirmed the existence of La in the prepared samples. In the PL spectra, La-sensitized samples exhibited three bands at 402 nm, 438 nm, and 463 nm in the visible range when excited at the 260 nm wavelength. As the proportion of La increased, the intensity of bands at 438 nm and 463 nm decreased, whereas the band at 402 nm remained stable. Time-resolved PL spectra illustrated the lifetime of the samples. Corresponding CIE co-ordinates for La-sensitized CaZrO3 were calculated.

Due to low power consumption, tunable wavelength and long lifetime ultraviolet light-emitting diodes (UV LEDs) have found many applications in different fields such as health care, water disinfection, agriculture. In this review, we report different problems that lead to low external quantum efficiency of UV LEDs. We also report various challenges in the growth process of the UV LEDs such as increase in the dislocation density, which affects the optoelectronic performance of the devices. We also report the analysis of the two modes of light polarization, i.e. transverse electric and transverse magnetic in UV LEDs. Moreover, we also summarize various state-of-the-art reported external quantum efficiencies, light output power and peak emission wavelengths in the three UV wavelength regimes, i.e. UV-A, UV-B and UV-C LEDs.

28 p.-5 fig., Light represents a signal for the regulation of virulence in many microbial pathogens. Two stone fruits, nectarines and cherries, were used to investigate the influence of light on brown rot caused by Monilinia laxa. Three single-spore strains were inoculated on nectarines and incubated under different white lights, red light, blue light, greenight, and black light with two photoperiods. In addition, to understand the effect of daylight irradiance on brown rot, M. laxa was inoculated on different cherry cultivars and incubated under two simulated solar irradiations. Significantly higher disease severity and sporulation were reported on inoculated nectarines incubated under 58 W white light for 12 hr light/12 hr darkness than on nectarines incubated in continuous darkness. Only red light caused a significant increase in the incidence and severity of the disease in nectarines inoculated with the three M. laxa isolates, compared to fruit incubated under white light. High light intensity (185.45 W/m2), caused greater brown rot severity in all cherry cultivars, both early and late varieties, than low irradiance (145.85 W/m2). Significant up-regulation of the pathogenicity-related MlPNL2 gene was observed as an early response after cherry inoculation under high-intensity light, especially in late cherry cultivars, while MlPG1 expression did not show any changes under different light irradiances. M. laxa was shown to be a light-responsive fungal pathogen, and light seemed to play an active role in brown rot development., This study was funded by grants AGL2014-55287-C2-1-R and AGL2017-84389-C2-2-R from the Ministry of Science, Innovation and Universities (MCIU, Spain), Agencia Estatal de Investigación (AEI) and the Fondo Europeo de Desarrollo Regional (FEDER, EU).

Nonlinear optical (NLO) materials are indispensable for laser frequency conversion, by which the output wavelength of laser can be greatly expanded. A prerequisite for the applications of NLO materials is that they must be optically transparent in the working spectral range. Although the widely used infrared (IR) NLO crystals such as AgGaS2 , AgGaSe2 , and ZnGeP2 have very broad mid-IR (2-20 μm) transparency, they are all inherently suffered by low laser-induced damage thresholds (LDTs). Oxide-based materials usually possess desirably high LDTs, however, most of them have quite limited IR transparency, typically, within 6 μm. In this Minireview, we focus on new oxide-based NLO materials showing exceptionally wide IR transparent ranges beyond 6 μm, in which significant developments have been achieved in recent years. Nine relevant NLO materials are investigated and analyzed from the aspects of design strategy, synthesis and large crystal growth, optical and NLO properties as well as composition-structure-property correlations. A brief perspective on the future research directions is also provided.

Background Recently, it become an important strategy using light to regulate plant growth and quality, especially on daily edible leafy vegetable. Pak-choi is rich in healthy functional compounds, e.g. flavonoid and glucosinolate. Many studies have focused on the plant response to increased radiation and transformed visible light quality, however, we know less about different blue and UV-A light wavelengths. Therefore, the goal of this study was to identify whether different blue and UV-A light wavelengths could improve quality in two cultivars of pak-choi and further cultivate potentially healthy functional plants. Results The different blue and UV-A light wavelength treatments significantly increased the fresh and dry weight in two cultivars of pak-choi. Compared with control, the content of soluble protein was higher after the different blue and UV-A light treatments. Similarly, the contents of total phenolics and total flavonoids increased significantly under the light treatments, and the highest content presented under T430 (supplemental blue light at 430 nm) in red-leaf pak-choi and under T400 (supplemental UV-A light at 400 nm) in green-leaf pak-choi. The total anthocyanins content and 2,2-diphenyl-1-picrylhydrazyl (DPPH) of two pak-choi cultivars improved positively with decreasing treatment wavelength, and other healthy compounds were affected to varying degrees under supplemental light treatments. Conclusion The growth and healthy compound contents of pak-choi were significantly improved by supplemental blue and UV-A light, and there were wavelength- and cultivar-dependent effects. Compared with control, T430 presented the higher biomass and the contents of total phenolics, flavonoids and pigment in two pak-choi cultivars, and T380 was an efficient strategy to increase antioxidants and health-promoting compounds of red-leaf pak-choi. © 2020 Society of Chemical Industry.

This chapter presents the basic concepts on propagation of light through optical fibre. Propagation of light through a specific medium can be explained in two ways: geometric optics and wave theory. The chapter describes geometric optics to explain the guidance of light through the optical fibre and to calculate the transmitted optical power as a function of wavelength. It explains the wave theory by using a scalar model and vector model of a multilayer cylindrical optical fibre. The chapter discusses the most important factors of fibre losses: absorption, Rayleigh scattering, macrobending, and microbending. There are two main groups of microstructured optical fibre for the propagation of light: hollow core fibre (HCF) and photonic crystal fibre (PCF). In a PCF, light is transmitted through silica and in a HCF, light is transmitted through the air. The chapter also provides a discussion on propagation of light in specialty optical fibres focused on sensing.

In laboratory acoustic experiments of Rayleigh waves, spatial resolution often suffers from the size effect of the acoustic receivers, which often cannot be scaled-down by the experimental wavelength used for model scaling due to the limitations of the acoustic technique. Based on scaled-down models with homogeneous and lateral inhomogeneous media, the laboratory experiments of Rayleigh waves are performed using acoustic and seismoelectric measurements, respectively. The measurements and resulting dispersion analysis indicate that the accompanying seismoelectric fields, which are measured by point-like electrodes, can represent the acoustic fields measured in the experiments by wide band acoustic receivers. Moreover, for the lateral inhomogeneous model, seismoelectric signals received by electrodes with a point-like size show more detail in the dispersion features of Rayleigh waves than do acoustic signals measured by acoustic receivers with a size close to that of the wavelength. This verifies that the r...

Arylazopyrazoles are an emerging class of photoswitches with redshifted switching wavelength, high photostationary states, long thermal half‐lives and facile synthetic access. Understanding pathways for a simple modulation of the thermal half‐lives, while keeping other parameters of interest constant, is an important aspect for out‐of‐equilibrium systems design and applications. Here, it is demonstrated that the thermal half‐life of a water‐soluble PEG‐tethered arylazo‐bis(o‐methylated)pyrazole (AAP) can be tuned by more than five orders of magnitude using simple pH adjustment, which is beyond the tunability of azobenzenes. The mechanism of thermal relaxation is investigated by thorough spectroscopic analyses and density functional theory (DFT) calculations. Finally, the concepts of a tunable half‐life are transferred from the molecular scale to the material scale. Based on the photochromic characteristics of E‐ and Z‐AAP, transient information storage is showcased in form of light‐written patterns inside films cast from different pH, which in turn leads to different times of storage. With respect to prospective precisely tunable materials and time‐programmed out‐of‐equilibrium systems, an externally tunable half‐life is likely advantageous over changing the entire system by the replacement of the photoswitch., Arylazopyrazoles are an emerging class of photoswitches with redshifted switching wavelength, high photostationary states, long thermal half‐lives and facile synthetic access. Understanding pathways for a simple modulation of the thermal half‐lives, while keeping other parameters of interest constant, is an important aspect for out‐of‐equilibrium systems design and applications. Here, it is demonstrated that the thermal half‐life of a water‐soluble PEG‐tethered arylazo‐bis(o‐methylated)pyrazole (AAP) can be tuned by more than five orders of magnitude using simple pH adjustment, which is beyond the tunability of azobenzenes.

The first fluorosulfonic ultraviolet (UV) nonlinear optical (NLO) material, C(NH2 )3 SO3 F, is rationally designed by taking KBe2 BO3 F2 (KBBF) as the parent compound. C(NH2 )3 SO3 F features similar topological layers as KBBF by replacing inorganic (BO3 )3- with organic C(NH2 )3 + trigonal units and BeO3 F with SO3 F- tetrahedra. Therefore, C(NH2 )3 SO3 F is a metal-free UV NLO crystal. Benefiting from the coplanar configuration of the C(NH2 )3 + cationic groups, it possesses a large SHG response of 5×KDP and moderate birefringence of 0.133@1064 nm. Besides, it has a short UV cutoff edge of 200 nm. The calculated results reveal the shortest SHG phase-matching wavelengths can reach 200 nm. These findings highlight the exploration of metal-free compounds as nontoxic and low-cost UV NLO materials as a new research area.

Wavelength and angle resolved scattering (WARS) reflectance measurements are attractive to the photovoltaic (PV) industry as a means of characterizing the light-trapping properties of a textured front surface. Moreover, at the PV module level, where a stack comprising of encapsulants and glass is present, large angle scattering can promote total internal reflection at the interfaces and redirect light back towards the solar cell, thus increasing the photocurrent of the device. In this work, we present WARS measurements of a KOH-etched random pyramid surface in the 6°-90° range and identify the main paths the photons experience through reflections from various facets of the pyramids. Our results, combined with ray-tracing predictions, show that a reassessment of the morphology for simulation inputs is advised for a more comprehensive description of the experimental light paths, due to a distribution of power across multiple scattering angles and a lower average pyramid base angle. In addition, we discuss the implications on the total amount of light trapped at the glass-air interface and show that for a typical encapsulant refractive index of 1.5, approximately 14.5% of the scattered light is predicted to be trapped by the fabricated pyramidal texture. This is a significant increase over the 3.8% calculated to be trapped when assuming a dihedral base angle fixed to 54.74°.