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A theoretical study has been performed on effect of polarization state of incident plane wave on performance of photonic nanojet (PNJ) generated by a sphere or an ellipsoid or an elliptical cylinder scatterer, among which the sphere has a higher while the ellipsoid and elliptical cylinder have a relatively low geometric symmetry. The study shows that the polarization state of incident wave affects mainly full width at half maximum of the PNJ in case of the sphere scatterer, whilst influences mainly the focal length in case that the scatterer is an ellipsoid or elliptical cylinder. Further study focuses on the effect on the focal length of the PNJ generated by either an ellipsoid or an elliptical cylinder scatterer, and the influences of type, geometric size and orientation of scatterer on the effect. The results show that the effect prefers to take place for a scatterer with a lower symmetry, and the type, geometric size and orientation of scatterer all can influence the effect. There exists a maximum effect at a certain symmetry and the maximum effect depends on the type, geometric size and orientation of scatterer. In the case of the elliptical cylinder, the focal length of PNJ generated can increase by as much as two times as the polarization state is changed. [ABSTRACT FROM AUTHOR]

The preparation of substituted phenols via a direct carbonyl desaturation is an intrinsic challenging task in modern synthetic chemistry. Herein, we develop a modular catalytic protocol for the synthesis of substituted phenols via the direct dehydrogenative aromatization of simple cyclohexanones in a metal‐free manner. A broad variety of substrates bearing an assortment of functional substituent groups are compatible with this protocol. Preliminary mechanistic investigations revealed that the reaction underwent a hydride leaving mechanism in the presence of a catalytic amount of tetrabutylammonium iodide. The current approach features simple operation, low reagent cost and green conditions. Insight gained from our studies is expected to advance general efforts towards the green synthesis of structurally diverse phenols via readily available raw materials, offering an alternative strategy for the carbonyl desaturation in organic synthesis. [ABSTRACT FROM AUTHOR]

Growth of Er3+‐doped 100‐nm thick LiNbO3(LN) films on Z‐cut LiTaO3(LT) single‐crystal by e‐beam evaporation and in‐situ anneal at 600–800°C was studied. Crystalline phase, crystallographic orientation, Er3+ spectroscopic properties, constituent element valence states, defects, Er3+ concentration and stoichiometry of the films were characterized. The results show that the films are in LN single‐crystal state and orient along with c crystallographic axis. Constituent elements Li, O and Er are present in their respective single valence states Li+, O2−, Er3+, while the Nb is in two valence states Nb5+ and Nb4+. The films have Li2O‐contents around congruent point. Antisite(NbLi4+) is the major defect. Its concentration decreases, while Li2O‐content, crystallinity degree, and fluorescence intensity increase with increased growth temperature. The presence of Er3+ in the grown films is in the form of LN crystalline phase. Its concentration is considerably lower than that in initial target material because of lower e‐beam evaporation efficiency of heavy Er3+. [ABSTRACT FROM AUTHOR]

Mode size converter enables to match two waveguides with different mode sizes. It has already become an indispensable component in modern integrated photonics. Here, we propose a strategy for implementing an on-chip mode size converter consisted of a gradient geometry metasurface and two cascaded waveguide tapers on the lithium-niobate-on-insulator platform. The metasurface, which is formed by a series of length-graded silica nanostrips embedded into LN waveguide, functions as focusing of incident wave and exaltation of conversion efficiency. A mode size converter that enables to match a fundamental TE 00 mode in a 10-μm-wide waveguide with that in a 0.8-μm-wide one was simulated to verify the feasibility of the strategy. We show that the device is not only compact with a length of 22.9 μm, but also shows an ultra-broad operation band as much as 1150 nm (from 1100 to 2250 nm), over which the conversion efficiency keeps >90 %. In addition, we show that the device has a good robustness to fabrication deviations. The strategy proposed here can be flexibly extended to other waveguide cross-section sizes and other guided modes. • A strategy is proposed for realizing an on-chip ultra-broadband mode size converter. • It uses gradient geometry metasurface and cascaded tapers on LNOI platform. • It is proved by simulating a device connecting a wide waveguide with a narrow one. • The device is valid for on-chip use and has an ultra-broad band as much as 1150 nm. • The strategy has a good scalability, the device has an excellent fabrication tolerance. [ABSTRACT FROM AUTHOR]

Er3+/Yb3+ doped LiNbO 3 (LN) single crystal films with varying Yb3+ doping level were grown on z -cut LiTaO 3 bulk single crystals via using e-beam evaporation method. The crystallographic orientation, elemental distribution, fluorescence properties, ionic valence states, Er3+ concentration, Yb3+ concentration and Li 2 O content of films were carefully studied. Results from XRD, SEM and Raman scattering conclude that the predominant phase of these films is LN and they are oriented along (006). The results of energy dispersive spectroscopy indicate that constituent elements are uniformly distributed over the entirety of the films. The visible and near-infrared luminescence intensities rise with increasing Yb3+-doping concentration. The Li 2 O content of films remains constant at 48.8 mol% with growing Yb3+-doping level based on the optical birefringence method, which is consistent with the Raman results. XPS results suggest that the Er3+ and Yb3+ concentrations in the films are lower than that in the polycrystalline powder since e-beam evaporation has a low efficiency of heavy Er3+ and Yb3+ ions. • The Er3+, Yb3+ doped LiNbO 3 single crystal thin films were grown by the e-beam evaporation method. • The fluorescence properties enhance clearly with a rise in Yb3+-doping concentration. • The accurate Li 2 O content have been evaluated by the birefringence method. • The Er3+ and Yb3+ concentration in the films have been calculated by the XPS. [ABSTRACT FROM AUTHOR]

• A thin-film lithium niobate TM-pass waveguide polarizer is proposed. • Subwavelength grating metamaterial for polarization generation. • Simulation shows that the device can operate with a bandwidth ∼415 nm. • The device shows reasonable extinction ratio and insertion loss. An ultra-broadband TM-pass waveguide polarizer based on thin-film LiNbO 3 -on-insulator waveguide and subwavelength grating (SWG) metamaterials is proposed and modeled. The device consists of an SWG in the central part and two coupling regions in the input and output sides. The SWG, formed by a series of bending nano-stripes, functions as a filter of polarization, and the two coupling regions serve to degrade mode mismatch loss. By tailoring the duty cycle of the SWG metamaterial, the SWG structure supports only the TM guided mode, while the TE guided mode is cutoff and thus filtered out. Simulation shows that, with a SWG meta-material formed by a series of 90°-bending nano-stripes, the polarizer can achieve an ultra-large bandwidth of ∼415 nm (1.26–1.675 μm) with an insertion loss < 1.1 dB and an extinction ratio > 29.4 dB. Moreover, the proposed polarizer tolerates a 5 nm deviation in both width and thickness of the nano-stripes. Such an ultra-broadband device may find its use in high-capacity optical communication systems, and is proposed firstly on the basis of the lithium-niobate-on-insulator platform, to the best of our knowledge. [ABSTRACT FROM AUTHOR]

• Polarization beam splitter based on LNOI triple-waveguide coupler is proposed. • α-Si nanostrip is used to manipulate the coupling of TM polarization mode. • Higher polarization extinction ratio and lower insertion loss are achieved. • The device is compact and suitable for on-chip applications. • A larger feature size (∼200 nm) that facilitates fabrication is involved. Polarization beam splitter (PBS) is a fundamental component of integrated photonics to manipulate wave polarization state, and most PBS devices were designed on the popular SOI. As an alternative, a PBS may be implemented on the basis of thin-film LiNbO 3 -on-insulator (LNOI), a promising platform for developing various compact or ultra-compact photonic active and passive devices. However, smaller modal birefringence of the LNOI waveguide makes it not easy to implement a PBS of high-performance. Here, we propose a compact, high-performance PBS on the basis of a triple-waveguide coupler consisted of two LNOI ridge waveguides and an amorphous silicon (α-Si) nanostrip assisted waveguide. By making use of the α-Si nanostrip, the PBS works in the case that the TM polarization mode meets the phase matching condition while the TE polarization mode does not. Numerical results show that the PBS is compact with a length of only 31 μm. The device can achieve an ultra-high polarization extinction ratio (>29.4 dB) and an ultra-low insertion loss (<0.066 dB) in the operating wavelength range of 1500–1600 nm for the TE polarization mode, and a polarization extinction ratio of > 20 dB and an insertion loss of < 0.16 dB over a ∼ 60 nm bandwidth from 1527 nm to 1587 nm for the TM polarization mode. Moreover, the device has a larger feature size that facilitates fabrication. Overall, this device has the advantages of compact size, higher polarization extinction ratio, lower insertion loss, and larger feature size, which is suitable for on-chip applications. [ABSTRACT FROM AUTHOR]

A post-growth Li-rich vapor transport equilibration (VTE) technique was used to prepare near-stoichiometric Er3+ doped LiNbO 3 thin films. Er3+ fluorescence property, defect feature and Li 2 O content of the films were characterized. The results show that the visible and near-infrared fluorescence intensity increases remarkably by ∼10 times the VTE time is increased from 0 to 5 h. The enhancement can be explained from viewpoint of Nb4+ defects concentration. X-ray photoelectron spectrometer study confirms presence of antisite Nb Li 4+ in the films and Nb Li 4+ is major defect. Its concentration decreases with increased VTE time. The Li 2 O content in the films is evaluated to be 48.8–49.7 mol% from the birefringence results. It increases with a rise in VTE time, matching with the characteristic of antisite defects. As defects concentration decreases, the non-radiative transition weakens , which is beneficial to improve fluorescence properties. • A Li-rich vapor transport equilibration technique was used to prepare near-stoichiometric Er3+ doped LiNbO 3 films. • Visible and near-infrared fluorescence intensity increases by ∼10 times as VTE time is increased to 5 h. • Li 2 O contents in the grown films were evaluated from measured birefringence to be from 48.8 to near-stoichimetric 49.7 mol%. • The enhancement can be explained from viewpoint of Nb4+ defects concentration measured by XPS. [ABSTRACT FROM AUTHOR]

• Photonic hooks (PHs) array generated by a multi–dielectric structure is studied. • PHs formation is ascribed to optical inhomogeneity of multi-dielectric structure. • PHs performance can be effectively tailored by geometric and optical parameters. • Both 1D and 2D PHs arrays bent outward or inward can be generated. • Both 1D and 2D PHs arrays show application potential in field of 3D manipulation. Generation of array of photonic hooks (PHs) by a multi–dielectric structure that consists of periodically arrayed scatterer units has been systematically studied. The study focuses on the effects of geometric and optical parameters of the multi–dielectric structure on the characteristics of generated PHs, especially their bending angles. These geometric and optical parameters include size, shape, refractive index and number of scatterer units, and their adjacent spacing. The results show that the spacing, size and refractive index play a predominant role in tailoring the performance of the PHs array, and the spacing affects mainly the characteristics of a pair of symmetrical PHs while the size and refractive index differences between scatterer units affect mainly those of asymmetrical PHs as a result of the introduction of optical inhomogeneity. In the aspect of scatterer shape, for a multi–dielectric structure that consists of some cylinders, as the light wave is incident parallel (perpendicular) to the cylinder axis, its scattering characteristics are similar to those of the multi–dielectric structure that consists of some cuboids (spheres). In particular, for a structure consisted of cylinders or cuboids with long length in the z direction, an intensive photonic nanojet is additionally generated and located between the paired PHs provided that the wave is incident perpendicular to the cylinder axis or the longest side of cuboid. In the aspect of scatterer unit number, the multi–dielectric structures of odd and even scatterer units generate PHs with different characteristics. The paired PHs generated by multi–dielectric structure with equal spacings always bend outward. However, the paired PHs may bend inward provided that the multi–dielectric structure is designed properly. We have also studied the features of 2D PHs array. The results show that the 2D PHs array displays similar features to the 1D case. The application potential of both 1D and 2D PHs arrays is evaluated. [ABSTRACT FROM AUTHOR]

• A TM-pass polarizer based on an air-slot embedded TFLNOI waveguide is proposed. • Designed structure supports only a TM mode while TE mode being in cut-off state. • A symmetric tetragonal dipyramid air-slot is designed to degrade insertion loss. • Both slot geometry and silica thickness take effects on polarization performance. • Optimal device shows good performance and ultra-compactness valid for on-chip use. An air-slot assisted TM-pass waveguide polarizer based on thin-film lithium niobate on insulator (TFLNOI) is proposed. It consists of a segment of ridge-type TFLNOI single-mode strip waveguide and an embedded air-slot. The air-slot has a symmetric tetragonal dipyramid structure consisted of a cuboid in the central part and two identical tetragonal pyramids in two sides, which function as polarization generation and adiabatic approximation to degrade insertion loss, respectively. Waveguide properties and transmission characteristics of the device were simulated using finite difference method. The results show that the waveguide structure with a properly designed geometry supports only a TM mode, while does not the TE mode, which is cut-off in the cuboid air-slot region. Slot length, width and silica substrate thickness all take considerable effects on the insertion loss and extinction ratio. Qualitative and comprehensible explanations are given for the effects. An optimized polarizer has been suggested that exhibits excellent polarization performance, including a larger extinction ratio of 28.4 dB, a lower insertion loss of 0.29 dB, and a broader bandwidth of ∼110 nm (1490–1600 nm) with an extinction ratio >20 dB and an insertion loss <0.5 dB. In addition, the proposed device has a length of only 13 µm satisfying on-chip use. [ABSTRACT FROM AUTHOR]

A thermodynamic study was performed on diffusion growth of Ga 3+ -doped LiTaO 3 (LT) thin film for integrated optics. Some Ga 3+ -doped LT thin films were grown on LT surface by in-diffusion of homogeneously coated Ga 2 O 3 film at the temperature range of (1273 to 1473) K. After growth, the refractive indices at Ga 3+ -doped and un-doped surface parts were measured by prism coupling technique and Li composition there was evaluated from the measured refractive indices. The results show that Ga 3+ dopant has small effect on the LT index. Li 2 O out-diffusion is not measurable. The Ga 3+ profile in the grown thin film was analysed by secondary ion mass spectrometry. It is found that the grown Ga 3+ ions follow a complementary error function profile. A thermodynamic model for Ga 3+ diffusion growth is suggested and verified experimentally. From the measured Ga 3+ profiles, some thermodynamic parameters were obtained. These include diffusivity, diffusion constant, chemical activation energy, solubility, solubility constant and enthalpy of solution. These parameters are crucial to design and growth of a desired Ga 3+ -doped LT thin film for integrated optics. Comparison shows that Ga 3+ grows in LT two orders faster than Ti 4+ because of its smaller radius. Ga 3+ diffusivity/solubility in LT is one order/1.5-fold lower than in LiNbO 3 because Ta has a larger atomic mass and hence a lower mobility than Nb. [ABSTRACT FROM AUTHOR]

Some Er 3+ -doped LiTaO 3 plates were prepared by in-diffusion of Er-metal film locally coated onto congruent Z -cut substrate in air at a wide temperature range from 1000 to 1500 °C. After diffusion, Er 3+ -doping effect on LiTaO 3 refractive index and Li 2 O out-diffusion arising from Er 3+ in-diffusion were studied at first. Refractive indices at the doped and undoped surface parts were measured by prism coupling technique and the surface composition was estimated. The results show that Er 3+ dopant has small contribution to the LiTaO 3 index. Li 2 O out-diffusion is slight (Li 2 O content loss <0.3 mol%) for the temperature below 1300 °C while is moderate (Li 2 O content loss <0.6 mol%) for the temperature above 1400 °C. The Er 3+ profile was studied by secondary ion mass spectrometry. The study shows that the diffused Er 3+ ions follow either a complementary error function or a Gaussian profile. Characteristic parameters including diffusivity, diffusion constant, activation energy, solubility, solubility constant and heat of solution were obtained and compared with the LiNbO 3 case. The comparison shows that the diffusivity and solubility in LiTaO 3 are considerably smaller than in LiNbO 3 because of the difference of Ta and Nb in atomic weight. [ABSTRACT FROM AUTHOR]

Er 3+ /Ti 4+ -co-doped LiNbO 3 plates were prepared by annealing congruent substrates coated with stacked Er- and Ti-metal films having different thicknesses and coating sequences. The crystalline phase, OH − absorption, Er 3+ -doping effect on LiNbO 3 refractive index and Li + -composition in the Er 3+ /Ti 4+ -co-doped layer were studied. The results show that the LiNbO 3 phase dominates in the co-doped layer, the Er 3+ -doping affects little the LiNbO 3 refractive index, slight Li 2 O out-diffusion occurred in the diffusion procedure, and the annealing procedure does not affect the OH − absorption band noticeably. The Er 3+ /Ti 4+ -co-diffusion characteristics were studied by secondary ion mass spectrometry. The study shows that Ti 4+ diffuses much faster than Er 3+ . The Ti 4+ co-diffusion assists and controls the Er 3+ -diffusion and Er 3+ diffusivity increases linearly with initial Ti-metal thickness. In contrast, neither Er-metal thickness nor coating sequence of Ti- and Er-metal films influences the Ti 4+ or Er 3+ diffusivity. The co-diffusion features are explained. A co-diffusion model is proposed. [ABSTRACT FROM AUTHOR]

The mutual influence of co-diffused Ti and Sc in LiNbO single-crystal was studied. Sc/Ti co-doped LN plates were prepared by annealing (at 1060 °C in wet O) Z-cut congruent LiNbO substrates coated with stacked ScO and Ti films, which have different thicknesses and coating sequences. After the annealing, the refractive index and composition at the undoped and Sc-only doped surface parts were characterized by prism coupling technique. The Sc and Ti profiles were analyzed by secondary ion mass spectrometry. The results show that the Sc-doping has little contribution to the LiNbO refractive index. LiO out-diffusion is not measurable. In the only diffusion case, the Sc diffuses five times slower than the Ti. In the Sc/Ti co-diffusion case, the Ti assists and controls the Sc diffusion. The Sc diffusivity increases linearly with the initial Ti-metal thickness. In contrast, the Sc affects the Ti diffusion little. Neither the ScO film thickness nor the coating sequence influences the diffusivity of the two ions. The co-diffusion features are explained. A model for the co-diffusion system is suggested and verified experimentally. The Ti:Sc:LiNbO planar and strip waveguide are optically characterized. The results show that the Sc presence does not affect the waveguide characteristics and the waveguide is optical-damage-resistant. [ABSTRACT FROM AUTHOR]

In this paper, we have tried to prepare MgAl2O4 spinel by molten salt synthesis using hydroxide as solvent. By controlling the amount of KCl in KOH, pure flower-like MgAl2O4 nanostructures could be synthesized at 1150 °C. Powder X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy were used to investigate the structures and morphologies of the obtained products. The results showed that the 3D flower-like nanostructures consisted of numerous 2D nanoflakes with a thickness of about several tens of nanometers. Further investigations on the possible formation mechanism revealed that a self-sacrificing template process dominated the formation of MgAl2O4 and the growth of the flower-like products was attributed to the competition between the growth rates along the directions perpendicular and parallel to the Al2O3 particle surfaces. Finally, an impedance-type humidity sensor was fabricated based on the flower-like MgAl2O4 nanostructures and tested for its humidity performance showing that the as-prepared MgAl2O4 nanostructures are suitable for high-performance humidity sensors. [ABSTRACT FROM AUTHOR]

Large amounts of MgAl 2 O 4 micro-rods were successfully synthesized using the molten-salt technology. The effect of KCl contents on the formation of MgAl 2 O 4 micro-rods was investigated. The structure and morphology of MgAl 2 O 4 were investigated by means of powder X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy, respectively. The experimental results showed that the contents of KCl significantly influenced the formation of MgAl 2 O 4 micro-rods. MgAl 2 O 4 micro-rods could be prepared at 1150 °C with a weight ratio of 100:1 between the salt and the starting materials. The formation of MgAl 2 O 4 micro-rods could be suggested to be due to the inhomogeneous nucleation and orientated growth perpendicularly to the surfaces of Al 2 O 3 grains. An impedance-type humidity sensor was finally fabricated based on the as-prepared MgAl 2 O 4 micro-rods. According to tests of the humidity performance, MgAl 2 O 4 micro-rods might be suitable for high-performance humidity sensors. [ABSTRACT FROM AUTHOR]

Zr4+/Ti4+-codoped LiNbO3 plates were prepared by local codiffusion of stacked ZrO2 and Ti metal films coated onto Z-cut congruent LiNbO3 substrates in wet O2 at 1060°C. The metal and oxide films have different thicknesses and coating sequences. After diffusion, the Zr4+ doping effect on the refractive index of LiNbO3 and the Li2O out-diffusion issue were studied by the prism coupling technique. The codiffusion characteristics of Zr4+ and Ti4+ were studied by secondary ion mass spectrometry. The results show that the Zr4+ doping has little contribution to the refractive index of the crystal. Li2O out-diffusion is not measurable. In the Zr4+-only diffusion case, the diffusivity of Zr4+ is four times smaller than that of Ti4+. In the Zr4+/Ti4+ codiffusion case, the Ti4+ codiffusion assists the Zr4+ diffusion. The Zr4+ diffusivity increases linearly by two more times with the increase in initial Ti film thickness from 0 to 200 nm. On the other hand, the Zr4+ affects the Ti4+ diffusion little. Neither the ZrO2 film thickness nor the coating sequence of Ti metal and ZrO2 oxide films influences the diffusivity of the two ions. All the codiffusion characteristics are explained. A Zr4+/Ti4+ codiffusion model is suggested that consists of two independent diffusion equations with a Zr4+ diffusivity dependent of Ti4+ concentration and a constant Ti4+ diffusivity. In addition, the existence of a waveguide in the Zr4+/Ti4+-codoped layer is verified experimentally, and the optical-damage-resistant feature of the waveguide is verified by two-beam hologram recording experimental results. [ABSTRACT FROM AUTHOR]

Multi-mode Ti:LiNbO 3 planar waveguide was fabricated by in-diffusion of 100-nm-thick Ti-metal film coated onto a near-stoichiometric LiNbO 3 substrate prepared by vapor transport equilibration. The crystalline phase and composition in the waveguide were characterized. The guided modes in the planar waveguide were characterized by prism coupling technique. The refractive index profile is constructed from the measured mode indices using the inverse Wentzel–Krames–Brillouin method, and correlated with the Ti 4+ - concentration profile, which was obtained from secondary-ion-mass-spectroscopy analysis. The results show that the waveguide still retains the LiNbO 3 phase, its composition is near-stoichiometric. The index change and Ti 4+ -concentration follow an exponential relationship with a power index 0.4 for an ordinary ray and 1.07 for an extraordinary ray. A comparison of various congruent and near-stoichiometric bulk materials or waveguides allows to conclude that the relationship is different from congruent to near-stoichiometric composition, from one fabrication method to another, and from bulk material to waveguide configuration. The difference is explained qualitatively. [ABSTRACT FROM AUTHOR]

Diffusion properties of Sc3+ in LiNbO3 crystal were studied, together with other two related issues: Sc3+-doping effect on LiNbO3 refractive index and Li2 O out-diffusion arising from Sc3+ in-diffusion. To reach the goal, some Sc3+-doped LiNbO3 crystal plates were prepared by in-diffusion of Sc2 O3 film coated onto Z-cut congruent substrates in air at different temperatures ranging from 1030°C to 1130°C. After diffusion, the refractive indices at the doped and undoped parts of surface were measured by prism coupling technique and the surface composition was evaluated from the measured index. The results show that the Sc3+ doping has little contribution to the substrate index and the Li2 O out-diffusion is not measurable. The Sc3+ profile was analyzed by secondary ion mass spectrometry. Some characteristic parameters such as temperature-dependent diffusivity, diffusion constant, activation energy, and surface concentration are obtained. The Sc3+/ Ti4+ co-diffusion characteristics were also studied. Comparison shows that in the single-diffusion case, the Sc3+ diffusivity is considerably smaller than the Ti4+ diffusivity. In the Sc3+/ Ti4+ co-diffusion case, the Ti4+ co-diffusion results in substantial increase in Sc3+ diffusivity while the Ti4+ diffusivity changing little. The diffusion characteristics are qualitatively explained. The Ti4+-assisted Sc3+ diffusion would be utilizable in shortening the fabrication period of an optical-damage-resistant Ti-diffused LiNbO3 waveguide doped with Sc3+, and some considerations for the fabrication are given. [ABSTRACT FROM AUTHOR]

A numerical study has been performed on electric field profile features of photonic nanojet generated by a SiO 2 microcylinder with a varied diameter. The study shows that a strong (44.2I 0) nanojet with 0.7λ lateral width and 7.8λ length can be obtained, which, as a line light source, has a potential for application in fields of nanopatterning and nanolithography. Along with the study on a single-layer microcylinder, we further studied the characteristics of the nanojet generated by a two-layer microsphere consisted of an interior LiNbO 3 microsphere and an exterior semiconductor layer, which have refractive indices of 2.34 and ~3.3 @ 500 nm, respectively. The study focuses on nanojet generation condition and the effects of refractive indices of microsphere materials and background, and working wavelength on electric field distribution characteristics of the nanojet. By immersing the two-layer microsphere into a proper liquid such as the de-ionized water, an ultra-long (>14λ), ultra-strong (>50I 0) and narrow enough (0.56λ) nanojet could be created. All of the characteristics and effects are qualitatively interpreted in terms of ray optics in combination with Mie scattering theory. [ABSTRACT FROM AUTHOR]

• Er3+/Yb3+:NaLa(WO 4) 2 phosphor was synthesized by solid-state reaction method. • The phosphor has a mean grain size 5 μm and a cutoff phonon energy 927 cm−1. • There exist optimal Er doping level of 5 mol% and Yb codoping level of 20 mol%. • The phosphor shows strong fluorescence, higher thermal stability and sensitivity. • The phosphor is promising for optical thermometry in a broad range of 293–800 K. Er3+/Yb3+-codoped NaLa(WO 4) 2 phosphor samples with different Er3+ and Yb3+ doping levels were synthesized by solid-state chemical reaction for optical thermometry and fully characterized. The results show that each phosphor sample mainly consists of NaLa(WO 4) 2 crystalline phase and has a nominally stoichiometric chemical composition. The phosphor grains have massive polyhedron morphology, good size homogeneity with a mean value of ∼5 μm and a cutoff phonon energy of 927 cm−1. The 530 and 550 nm upconversion fluorescence of Er3+ in the phosphor samples and their temperature characteristics were investigated under 980 nm excitation. The results show that the phosphor exhibits strong upconversion fluorescence and the maximum fluorescence intensity is observed at the optimal Er3+ and Yb3+ doping levels of 5 and 20 mol%, respectively. The two-photon process is responsible for the upconversion fluorescence. The spectral structure of either 530 or 550 nm fluorescence band is thermally stable. The peak absolute thermal sensitivity is observed at ∼490 K and has a peak value of ∼9 × 10-3 K-1. As expected, Er3+ or Yb3+ doping level has little effect on the thermal sensitivity. The phosphor displays a wide dynamical response range of thermal sensitivity from 293 to 800 K, where the sensitivity varies within (6.5–9.0) × 10-3 K-1. A comparison study shows that the temperature characteristics obtained from the cooling procedure are almost the same as those obtained from the heating procedure. Besides, the effects of Er3+/Yb3+ doping level and heating/cooling on fluorescence color chromaticity were also studied. Based on the results, the Er3+/Yb3+-codoped NaLa(WO 4) 2 phosphor shows strong fluorescence, good thermal stability, high thermal sensitivity and broad response range of thermal sensitivity. Thus, it is a promising material for thermal detection over a wide temperature range of 293−800 K. [ABSTRACT FROM AUTHOR]

Photonic jet (PJ) is generated by illuminating a dielectric scatterer with symmetric four Airy beams (SFAiB). The PJ properties have been systematically studied as a function of characteristic parameters of both the SFAiB and the scatterer, including the geometric parameter D that controls lateral position of each Airy beam component, decay factor, focal point position of the SFAiB, as well as the refractive index of the scatterer. The results show that the PJ performance can be optimized by all of these parameters as a result that the diffraction and self-focusing effects of the SFAiB itself, and the scatterer's focusing function simultaneously play roles in the PJ generation in case of SFAiB illumination. The illumination by SFAiB has advantages over that by plane wave or Gaussian beam in flexibility of tailoring the PJ performance and in possibility of generating a photonic hook with asymmetric illumination caused by transverse offset of focal point of incident SFAiB. In addition, the SFAiB illumination makes it possible to generate a PJ outside a scatterer in case that the scatterer has a higher refractive index of n s > 2.0, increasing the flexibility in both material choice and structural design of scatterer for generation of a PJ for some potential applications. • Photonic jet (PJ) is generated by symmetric four Airy beams (SFAiB) illumination. • SFAiB's diffraction and self-focusing, scatter's focusing effects enable to tailor PJ performance. • SFAiB illumination has advantages over that by plane wave or Gaussian beam. • The merits include flexibility in tailoring PJ performance and possibility of generating a photonic hook with asymmetric illumination. • SFAiB illumination enables to generate a PJ outside a scatterer with a higher refractive index of n s > 2.0, increasing flexibility in material choice and structural design of scatterer. [ABSTRACT FROM AUTHOR]

Background: The pathogen of angiostrongyliasis is the parasite Angiostrongylus cantonensis, and the transcriptome profiling of the male adult was unclear. We aimed to understand how the male adults adapt, so the expression profile of A. cantonensis adult males was analyzed. Methods: In order to improve the understanding of the transcriptome of adult males, RNA from three groups of male adult A. cantonensis was extracted and reverse transcribed to construct cDNA libraries. After sequencing, annotation of unigenes and transcripts was performed by querying the NR (Non- Redundant Protein Sequence Database), GO (Gene Ontology) and COG/ KOG (Clusters of Orthologous Groups of proteins/euKaryotic Ortholog Groups) databases. Results: For each group of adults, 43,260,894 raw reads and 43,200,341 clean reads were obtained. After successful assembly, 87,649 unigenes and 146,895 transcripts were obtained. Annotation of the unigenes and transcripts was identical and male adults expressed a series of genes encoding proteins specific to the male gender at the adult stage, such as proteins involved in energy metabolism, energy synthesis and transport. Expression of the ribosome pathway suggests a relationship with the physical activities during the adult male stage. Conclusion: The transcriptome analysis is a good reference to understand further the expression profile of male adult A. cantonensis. [ABSTRACT FROM AUTHOR]

• Human awareness detection dynamically reacts to high-altitude environment. • Early and late components co-mediate the reaction with exposure duration. • Opposite change of two components as a response to the reduced cognitive resources. • Increased late component and fast reaction resist high-altitude exposure. The psychological effects of long-term exposure to high-altitude environments have attracted great attention. These effects are usually attributed to the diminished cognitive resources due to high-altitude exposure. This study employed electroencephalography (EEG) to investigate the effects of exposure duration on awareness detection tasks. Neither reaction time nor accuracy showed the direct effects of the exposure duration, so did the model indexes obtained from drift diffusion model analysis. However, event-related potentials (ERP) analysis revealed that exposure duration was associated with changes in the visual awareness negativity (VAN) and the late positivity (LP) components, which in turn affected reaction time. Specifically, longer exposure durations were associated with lower VAN and higher LP, resulting in shorter reaction times and greater drift rate. In contrast to previous studies, the reverse relationship between VAN and LP may reflect a compensatory response to the reduced cognitive resources caused by high-altitude exposure. Additionally, increased LP and shorter reaction times with exposure duration may reflect a resistance to the high-altitude environment. We also conducted time–frequency analysis and found that theta power did not vary with exposure duration, suggesting that the reduction in cognitive resources remains stable in these individuals over time. Overall, our study provides new insights into the dynamic effects of high-altitude environments on awareness detection in the presence of reduced cognitive resources. [ABSTRACT FROM AUTHOR]

• The Y-junction and T-junction 1 × 2 power splitters based on LNOI platform are designed by an intelligent algorithm. • The combination of GA and FEM based on "Phc-like" structure is proposed. • Symmetric operations and two-dimensional models are used to improve optimization efficiency. • The optimized devices offer good performance and ultra-compact footprints suitable for on-chip use. Optical power splitters are critical components of photonic integrated circuits based on the lithium-niobate-on-insulator (LNOI) platform. However, the lithium niobate power splitters designed by traditional strategies are usually large in size, which limits their practical applications for on-chip high dense integration. Here, we focus on the efficient design of ultra-compact power splitters based on the LNOI platform. The Y-junction and T-junction 1 × 2 power splitters based on photonic-crystal-like (PhC-like) structures are designed by a genetic algorithm. The footprint of the functional region for Y-junction and T-junction power splitters are only 2.6 μm × 2.6 μm and 2.85 μm × 4.94 μm, respectively. Simulation results show that the insertion losses are about 0.1 dB and 0.7 dB at 1550 nm for these two kinds of devices. This work can as a generic approach for designing various ultra-compact functional devices based on LNOI platform. [ABSTRACT FROM AUTHOR]

• Polarization beam splitter(PBS) based on LNOI triple-waveguide coupler is proposed. • A plasmonic waveguide is used to exalt modal birefringence and control TM mode coupling. • Good performance of high polarization extinction ratio and low insertion loss is expected. • The device has compact size for on-chip application and definite fabrication tolerance. • Present work offers a promising strategy for compact, efficient PBS based on LNOI. A compact polarization beam splitter based on a triple-waveguide plasmonic directional coupler is proposed and modeled. The directional coupler consists of two usual lithium-niobate-on-insulator (LNOI) ridge waveguides and a metal-capped plasmonic LNOI waveguide located between them. It utilizes stronger polarization dependence of modal birefringence of a plasmonic waveguide. By appropriately designing the plasmonic waveguide geometry, the TM component wave meets the resonant coupling condition and outputs at cross port. Instead, the TE component wave does not meet the resonant coupling condition, cannot be resonant in the triple-waveguide directional coupler and outputs at through port directly. Excellent performance is expected for an optimal device. First, the device shows an ultra-high polarization extinction ratio(PER) of 28.3 dB and an ultra-low insertion loss(IL) of 0.06 dB for the TE-polarized wave, and of 31.7 dB and of 0.31 dB in order for the TM-polarized wave. Second, the working bandwidth with PER > 25 dB and IL < 0.08 dB is 100 nm (1500–1600 nm) for the TE-polarized wave, and that with PER > 20 dB and IL < 0.4 dB is 30 nm (1534–1564 nm) for the TM-polarized wave. Third, the device has a compact structure of 33 μm in length and exhibits definite fabrication tolerance. Overall, the proposed device exhibits ultra-high PER and ultra-low IL, and has a compact size suitable for on-chip use. A comparison shows that present device exhibits advantage in IL and/or size over that based on other LNOI structures or the SOI platform. [ABSTRACT FROM AUTHOR]

A new aluminum ion fluorescent probe (4-(diethylamino)-2-hydroxybenzylidene)isoquinoline-1-carbohydrazide (HL 1 ) has been conveniently synthesized and characterized. HL 1 exhibited a highly selective and pronounced enhancement for Al 3+ in the fluorescence emission over other common cations by forming a 2:1 complex, with a recognition mechanism based on excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT). The strong fluorescent emission can be observed even at ppm level concentration of the probe in the presence of Al 3+ with 41 fold intensity enhancement at 545 nm. HL 1 displays good linear relationship with Al 3+ in the low concentration and the limit of detection is 8.08 × 10 −8  mol/L. Similar molecules with different substituents on salicylaldehyde phenyl ring were synthesized for studying the structure-activity relationship. Density-functional theory (DFT) calculations are in agreement with the proposed mechanism. It is confirmed that HL 1 could be used to detect Al 3+ ions in real sample by fluorescence spectrometry and Al 3+ ions in cells by bioimaging. [ABSTRACT FROM AUTHOR]

The morphology of the hippocampus and amygdala can be significantly affected by a long-term hypoxia-induced inflammatory response. Cardiorespiratory fitness (CRF) has a significant effect on the neuroplasticity of the hippocampus and amygdala by countering inflammation. However, the role of CRF is still largely unclear at high altitudes. Here, we investigated brain limbic volumes in participants who had experienced long-term hypoxia exposure in Tibet (3680 m), utilizing high-resolution structural images to allow the segmentation of the hippocampus and amygdala into their constituent substructures. We recruited a total of 48 participants (48 males; aged = 20.92 ± 1.03 years) to undergo a structural 3T MRI, and the levels of maximal oxygen uptake (VO2max) were measured using a cardiorespiratory function test. Inflammatory biomarkers were also collected. The participants were divided into two groups according to the levels of median VO2max, and the analysis showed that the morphological indexes of subfields of the hippocampus and amygdala of the lower CRF group were decreased when compared with the higher CRF group. Furthermore, the multiple linear regression analysis showed that there was a higher association with inflammatory factors in the lower CRF group than that in the higher CRF group. This study suggested a significant association of CRF with hippocampus and amygdala volume, which may be related to hypoxic stress in high-altitude environments. A better CRF reduced physiological stress and a decrease in the inflammatory response was observed, which may be related to the increased oxygen transport capacity of the body. [ABSTRACT FROM AUTHOR]

Generation of multiple photonic hooks (PHs) at THz region in reflection mode by a multi-dielectric structure that consists of periodical or aperiodical scatterer units on top surface of a reflection screen has been systematically studied. The study focuses on effects of geometric and optical parameters of the multi-dielectric structure on characteristics of the PHs generated, especially the bending angle. These geometric and optical parameters include spacing between adjacent scatterer units, length of reflection screen, as well as the size, refractive index and number of scatterer units. The results show that these geometric and optical parameters are key factors in tailoring the performance of the multiple PHs generated. The spacing determines bending direction of PHs and there exists a critical spacing value. Smaller than this critical value, the PHs generated bend outwards. Larger than this critical value, the PHs bend inwards. In addition, the spacing can be also used to effectively adjust the intensity and bending angle of the PHs. Screen length affects mainly PH's bending. The size and refractive index differences between scatterer units introduce additional optical inhomogeneity that leads to the generation of asymmetrical multiple PHs. Finally, the possibility of generation of an arrayed PHs in the reflection mode is demonstrated. • Generation of photonic hooks (PHs) array in reflection mode is studied. • PHs formation is ascribed to optical inhomogeneity of multi-dielectric structure. • PHs performance can be effectively tailored by geometric and optical parameters. • PHs generated at smaller or larger spacing bend in opposite directions. • Optical-axis asymmetric structure generates asymmetrical PHs array. [ABSTRACT FROM AUTHOR]

A theoretical study has been performed on 1.76 μm on-chip amplification characteristics of Tm3+ in a rib waveguide of LiNbO 3 on insulator (Tm:LNOI) under 795 nm wavelength pumping. Steady-state rate equations and propagation equations of signal and pump waves are established on the basis of a three-level model of Tm3+ system with the cross relaxation process 3H 4 →3F 4 : 3H 6 →3F 4 included. The validity of the three-level model is demonstrated by referencing previously reported experiment result of Er3+-doped LNOI waveguide amplifier and by examining the effect of Tm3+ blue upconversion emissions on the 1.76 μm amplification. Besides the relations of signal gain to propagation length, launched pump power and input signal power, the effects of waveguide cross-section geometry and Tm3+ concentration on the gain characteristics are also studied. The results show that the waveguide cross-section geometry affects definitely the gain performance via its effect on mode field. The Tm3+ concentration affects the signal gain also via its effect on the 3H 4 →3F 4 : 3H 6 →3F 4 cross relaxation coefficient, besides the conventional effect that higher active ion concentration yields larger signal gain. A comparison with conventional Ti4+(Zn2+)-diffused Tm3+-doped LN [Ti(Zn):Tm:LN] waveguide shows that the Tm:LNOI waveguide has much better gain performance than the Ti(Zn):Tm:LN waveguide, including much stronger pump power and propagation distance dependences of signal gain, much higher signal gain and much lower threshold pump power. These features are associated with significantly increased Tm3+ population inversion extent due to ultra-compact mode field and larger overlapping factor of mode field and Tm3+ population profiles in the Tm:LNOI waveguide. • 1.8 μm amplification in Tm:LNOI waveguide is simulated based on three-level model. • Quantitative relations of signal gain to controllable parameters are established. • Tm:LNOI amplifier is more efficient than Ti(Zn):Tm:LN due to ultra-compact mode. • Waveguide cross-section geometry affects definitely gain via its effect on mode field. • Tm3+ concentration affects gain via its effect on cross relaxation process. [ABSTRACT FROM AUTHOR]

Low-loss gallium(Ga 3+ )-diffused erbium(Er 3+ )-doped LiTaO 3 (Ga:Er:LiTaO 3 ) channel waveguide was fabricated using erbium metal film diffusion followed by photolithographically patterned gallium oxide(Ga 2 O 3 ) strip diffusion. Secondary ion mass spectrometry analysis shows that Er 3+ concentration follows a Gaussian profile, Ga 3+ concentration follows a sum of two error functions at the waveguide surface and a Gaussian profile in the depth direction. Optical studies show that the waveguide supports single-mode propagation at 1.5 μm wavelength with a coupling loss <1 dB and a waveguide loss 0.2(0.3) dB/cm for the TE(TM) mode, and with a small polarization dependence in mode field distribution. Stable optical gain of ∼1.0 dB/cm was measured at 1547 nm wavelength with 220 mW pump power of 980 nm wavelength, indicating good photorefractive damage resistance of the waveguide. [ABSTRACT FROM AUTHOR]

• Er3+/Yb3+:GdNbO 4 micron-sized phosphor was synthesized by solid-state method. • Er3+ and Yb3+ concentrations have apparent effects on grain morphology. • The phosphor shows strong UCL, good thermal stability and adequate sensitivity. • The phosphor shows good chemical stability in high salinity environment. • The phosphor is promising for both thermometry and maritime protection. Micron-sized GdNbO 4 :Er3+/Yb3+ phosphors were prepared by employing a high-temperature solid-state reaction. The crystalline phase, morphology, composition, spectroscopic properties, and impact of rare-earth ion concentration, temperature and high salinity environment were systematically characterized. The extracted results show that phosphor is dominated by the existence of the GdNbO 4 crystalline phase. Their morphology and agglomeration phenomenon are strongly dependent on the rare-earth concentration. The phosphor exhibits also excellent up-conversion luminescence (UCL) properties under 980 nm excitation, while a two-photon process accounts for UCL. The following optimal concentrations were selected for enhanced UCL intensity: 10 mol% for Yb3+ and 3 mol% for Er3+. The phosphor shows excellent thermometric performances including strong UCL, good thermal stability, appropriate sensitivity and a wide sensitivity response range. To evaluate the accuracy of the present optical thermometer, the temperature of a heated bench has been comparatively measured by using the proposed optical thermometer and a commercial thermocouple with an accuracy of 1 K. By comparing the temperature values measured by the two methods, it can be concluded that the present optical thermometer has an accuracy better than 1.6 K. In addition, the phosphor exhibits good chemical stability in high salinity environment. Interestingly, its crystalline phase, structure, and UCL spectral structure, intensity and color are all preserved after one-month immersion into a high salinity solution. [Display omitted] GdNbO 4 :Er3+/Yb3+ phosphor was prepared by high-temperature solid-state method. Crystalline phase, morphology, composition, spectroscopic properties, and effects of rare-earth concentration, temperature and high salinity environment were fully characterized. The results show that the phosphor is promising for dual-application in thermometry and safety marks for maritime protection. [ABSTRACT FROM AUTHOR]

Without any templates, hollow structured La 2 Mo 2 O 9 particles are successfully prepared at room temperature by an ageing-assisted salt solvent process. Powder X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy are used to investigate structure and morphologies of the obtained products. It is found that the ageing process has a significant influence on the particle morphology evolution when the mixed precursors are disposed at room temperature. With the ageing time changed from one week to 12 weeks, the particles morphologies evolve gradually from ellipsoid to sphere. The as-prepared hollow structured La 2 Mo 2 O 9 spheres have an average diameter of about 800 nm and shell thickness of about 100 nm. For elucidating the possible formation mechanism, the influences of the single salt on the particles morphologies evolution are also investigated. The final results indicate KCl is a key factor for formation of La 2 Mo 2 O 9 spheres and the formation of the hollow structure should have close relations with the surface tension in the ageing assisted process. [ABSTRACT FROM AUTHOR]

Previous research has established a strong link between attention and visual mental imagery, but it's remained uncertain whether attention networks influence individual differences in the vividness of visual mental imagery. In our study, we examined 140 participants, assessing the vividness of imagery using the Vividness of Visual Imagery Questionnaire in both eyes-open and eyes-closed conditions. We employed the Attention Network Test, coupled with EEG recording, to characterize three attention sub-networks: alerting, orienting, and executive control. To pinpoint the specific attentional networks associated with the vividness of visual mental imagery, we utilized latent profile analysis to categorize participants into distinct subgroups. Additionally, we constructed a regression mixture model to explore how attention networks predict different latent categories of visual imagery vividness. Our findings revealed that the efficiency of the alerting network, as indicated by the N1 component, demonstrated a positive correlation with the vividness of visual imagery. This electrophysiological evidence underscores the role of the alerting network in shaping individual differences in the vividness of visual mental imagery. [ABSTRACT FROM AUTHOR]

• On-chip 1.53 μm amplification in Er:LNOI micro-photonic amplifier was simulated. • The simulation was performed in comparison with Ti:Er:LiNbO 3 waveguide amplifier. • Numerical model is confirmed by consistency of numerical and experimental results. • The Er:LNOI amplifier is more efficient than the Ti:Er:LiNbO 3 waveguide. • Due to higher Er3+ population inversion extent and ultra-compact mode of Er:LNOI. On-chip 1.53 μm amplification in 980-nm-pumped Er3+-doped lithium niobate on insulator (Er:LNOI) photonic wire (PW) has been studied theoretically in comparison with that in Ti:Er:LiNbO 3 waveguide on the basis of three- and six-level models of Er3+. We show that the six-level model gives more accurate analysis and its validity is confirmed by comparing the simulated results with the previously reported experiment data. The study shows that the Er:LNOI PW has a larger Er3+ population inversion extent than the Ti:Er:LiNbO 3 because of larger overlapping factor of mode field and Er3+ population profiles, and ultra-compact mode field. As a result, the Er:LNOI PW displays better gain performance than the Ti:Er:LiNbO 3 as described below. (1) Maximum/saturation gain of Er:LNOI PW can be as much as two/three times higher than that of the Ti:Er:LiNbO 3. (2) Gain of the Er:LNOI PW increases with propagation length more strongly in the initial stage and decreases more slowly beyond optimal length. It also shows stronger dependences on both pump power (in the initial stage) and signal power. (3) Gain in the Er:LNOI PW saturates more easily, and the Er:LNOI PW has a threshold pump power one order of magnitude lower than the Ti:Er:LiNbO 3. [ABSTRACT FROM AUTHOR]

Diffusion-doping is an effective, practical method to improve material properties and widen material application. Here, we demonstrate a new physical phenomenon: diffusion control of an ion by another in LiNbO3 and LiTaO3 crystals. We exemplify Ti4+/Xn+ (Xn+ = Sc3+, Zr4+, Er3+) co-diffusion in the widely studied LiNbO3 and LiTaO3 crystals. Some Ti4+/Xn+-co-doped LiNbO3 and LiTaO3 plates were prepared by co-diffusion of stacked Ti-metal and Er-metal (Sc2O3 or ZrO2) films coated onto LiNbO3 or LiTaO3 substrates. The Ti4+/Xn+-co-diffusion characteristics were studied by secondary ion mass spectrometry. In the Xn+-only diffusion case, the Xn+ diffuses considerably slower than the Ti4+. In the Ti4+/Xn+ co-diffusion case, the faster Ti4+ controls the diffusion of the slower Xn+. The Xn+ diffusivity increases linearly with the initial Ti-metal thickness and the increase depends on the Xn+ species. The phenomenon is ascribed to the generation of additional defects induced by the diffusion of faster Ti4+ ions, which favors and assists the subsequent diffusion of slower Xn+ ion. For the diffusion system studied here, it can be utilized to substantially shorten device fabrication period, improve device performance and produce new materials. [ABSTRACT FROM AUTHOR]

Fluorescence and absorption spectra at 530 nm (2H11/2→4I15/2), 560 nm (4S3/2→4I15/2), 660 nm (4F9/2→4I15/2), 980 nm (4I11/2→4I15/2), 1530 nm (4I13/2→4I15/2), and 2710 nm (4I11/2→4I13/2) of Er3+ in Gd3Ga5O12 single‐crystal codoped with Pr3+ have been measured. Judd‐Ofelt analysis yields the intensity parameters Ω2 = (0.68 ± 0.03) × 10−20 cm2, Ω4 = (0.60 ± 0.07) × 10−20 cm2, and Ω6 = (0.90 ± 0.17) × 10−20 cm2. A comparison with previously reported values of Er3+‐only doping case shows that Pr3+‐codoping causes slight change of both Ω2 and Ω4, while onefold increase of Ω6. From calculated radiative rates and measured fluorescence spectra, Er3+ emission cross‐section spectra were calibrated at first. Then, the absorption cross‐section spectra were calculated using McCumber relation. In parallel, the absorption cross‐section spectra were also obtained from the measured absorption spectrum, and compared with those obtained from the McCumber relation. The comparison shows that both methods give consistent result of absorption cross‐section spectrum. Further comparison with Er3+‐only doping case shows that Pr3+‐codoping causes considerable change of Er3+ cross‐section value. In spectrally mixing regions of Er3+ and Pr3+, Pr3+ emission affects little the determination of Er3+ emission cross‐section as Pr3+ fluorescence is much weaker than Er3+ fluorescence due to low Pr3+ concentration. [ABSTRACT FROM AUTHOR]

In the previous paper "Optical and Judd‐Ofelt spectroscopic study of Er3+‐doped strontium gadolinium gallium garnet single‐crystal" (J Am Ceram Soc. 2019;102:873–878), we have reported optical and Judd‐Ofelt spectroscopic properties of Er3+‐doped strontium gadolinium gallate (SrGdGa3O7) single‐crystal, and the Judd‐Ofelt study was performed on the basis of unpolarized absorption spectrum of the crystal. Present work reports the corrected unpolarized absorption spectrum and Er3+ concentration in the crystal, and hence corrected Judd‐Ofelt spectroscopic properties and cross‐section data. In addition, the polarization effect was considered in the Judd‐Ofelt analysis on the basis of polarization‐resolved absorption spectra. Effective Judd‐Ofelt parameters are presented and discussed in comparison with the results from the unpolarized spectrum, and consistent results have been obtained. This study also considers the effects of some other factors on the Judd‐Ofelt parameters. These include Er3+ concentration and selection of Er3+ absorption bands for the Judd‐Ofelt analysis. [ABSTRACT FROM AUTHOR]

A previous paper [D. K. Sardar et al., J. Appl. Phys. 93(5), 2602 (2003)] has reported Judd–Ofelt (J–O) spectroscopic properties of Er3+ in garnets Y3Al5O12, Y3(Sc2Ga3)O12, and Gd3Ga5O12. In that paper, the possible magnetic-dipole contribution to the oscillator strength, which is non-zero for the 4I13/2 ↔ 4I15/2 (1.5 μm) transition of Er3+, has been erroneously omitted in their J–O calculation, resulting in incorrect results of relevant spectroscopic parameters. In this Comment, we point out the error, perform correct J–O analysis, and report correct results. [ABSTRACT FROM AUTHOR]

• The shorter access time was more explained by the lower threshold. • The heart rate predicted the access time and threshold at high altitudes. • The cardiac deceleration-acceleration pattern was slightly various at high-altitudes. Many studies have indicated a strong relationship between cardiac and brain activities, both of which are sensitive to high-altitude exposure. This study combined a consciousness access task and electrocardiograms (ECG) to uncover conscious awareness in response to high-altitude exposure and its relation to cardiac activity. When compared with the low-altitude groups, the behavioral results showed that the high-altitude participants shortened the time of access to visual awareness of grating orientation, which was accompanied by a faster heart rate, excluding the influence of pre-stimulus heart rate, extent of cardiac deceleration after presenting the stimulus, and task difficulty. Although there were post-stimulation cardiac deceleration and post-response acceleration at both high and low altitudes, a slight increase in heart rate after stimulation at high altitudes may indicate that participants at high altitudes could quickly readjust their attention to the target stimulus. More importantly, the drift diffusion model (DDM) was used to fit the access time distribution of all participants. These results suggest that shorter time at high altitudes might be due to the lower threshold, suggesting that less evidence in high-altitude participants was required to access visual consciousness. The participants' heart rates also negatively predicted the threshold through a hierarchical drift diffusion modeling (HDDM) regression. These findings imply that individuals with higher heart rates at high altitudes have a greater cognitive burden. [ABSTRACT FROM AUTHOR]

Abstract Visible and infrared absorption and emission spectra of Er3+-doped strontium gadolinium gallate (SrGdGa 3 O 7) single-crystal were measured at room temperature. From the measured fluorescence spectra, the Er3+ emission cross section spectra were calculated at first. Then, by utilizing McCumber relation, the absorption cross section spectra were further calculated. In parallel, the absorption cross section spectra were also calculated from the measured absorption spectra of the crystal, and compared with those spectra calculated from the McCumber relation. The comparison shows that the absorption cross section spectra obtained using the McCumber relation are in reasonable agreement with those deduced from the measured absorption spectrum. Graphical abstract Visible, near-infrared, and mid-infrared emission and absorption cross section spectra of Er3+ in SrGdGa 3 O 7 single-crystal have been calibrated from measured fluorescence spectra using the McCumber theory. The absorption cross-section spectrum was also calibrated from the measured absorption spectrum. Comparison shows that the absorption cross section spectra calibrated from the McCumber theory are reasonably consistent with those from the absorption spectrum. Present work presents complete cross section knowledge of the studied crystal. fx1 [ABSTRACT FROM AUTHOR]

Abstract Optical and spectroscopic properties of Er3+/Pr3+-codoped Gd 3 Ga 5 O 12 single-crystal grown by Czochralski method have been studied. Absorption spectrum of the crystal was measured at room temperature and Er3+ absorption cross-section spectral distributions were calibrated from it. The Er3+ spectroscopic properties were analyzed on the basis of the Judd-Ofelt theory. Fundamental spectroscopic parameters were obtained that include absorption coefficient, cross-section spectral distribution, electronic transition oscillator strength, Judd-Ofelt parameters, fluorescence branch ratio, transition probability, radiative and fluorescence lifetimes, and quantum efficiency as well. Study shows that Pr3+-codoping results in substantial change of Er3+ spectroscopic properties, in qualitative consistent with the previous fluorescence studying result. In addition, refractive index of the crystal was measured at different wavelengths using prism coupling method, and the Sellmeier equation reported previously for Er3+-only doped Gd 3 Ga 5 O 12 crystal is corrected. Highlights • Juud-Ofelt spectroscopic properties of Er3+/Pr3+:Gd 3 Ga 5 O 12 crystal were studied. • Pr codoping results in substantial increase of the Judd-Ofelt parameters. • Pr codoping induces shortening of Er3+ 2.7 and 1.5 μm lifetimes from ms to sub-ms. • The effect is related to two resonant energy transfers from Er3+ to Pr3+. • Different efficiencies of the two transfers enable to realize 2.7 μm lasing. [ABSTRACT FROM AUTHOR]

Er3+‐doped strontium gadolinium gallium garnet (SrGdGa3O7) single‐crystal was grown by Czochralski method. The Er3+ concentration in the crystal was determined as 4.2 × 1021 ions/cm3 by inductively coupled plasma atomic absorption spectroscopy. Refractive index of the crystal was measured at the wavelengths of 633, 1311 and 1553 nm by prism coupling technique. The results show that the crystal is a positive uniaxial crystal with a birefringence of ~0.01, and the Sellmeier equation reported previously for the crystal doped with Nd3+ is also valid for the one doped with Er3+. Unpolarized absorption spectrum of the crystal was measured at room temperature and the Er3+ absorption cross‐section spectrum was calibrated from it. The Er3+ spectroscopic properties were studied by Judd‐Ofelt theory. Some fundamental spectroscopic parameters were obtained that include absorption coefficient and cross‐section spectral distributions, electronic transition oscillator strength, Judd‐Ofelt parameters, fluorescence branch ratio, transition probability, radiative and fluorescence lifetimes, and quantum efficiency. [ABSTRACT FROM AUTHOR]

Abstract Gallium-diffused lithium niobate (LiNbO 3) channel optical thin-film was fabricated by diffusion of photolithographically patterned gallium-oxide stripes on a Z-cut congruent LiNbO 3 substrate. Composition, optical properties of the channel thin-film and gallium diffusion profiles were characterized. The results show that the thin-film is in congruent composition environment, confines single-mode ordinary and extraordinary waves with a loss <0.5 dB/cm at 1.5 μm wavelength. The confined mode field follows Gaussian/Hermite-Gaussian profile in the width/depth direction of the channel thin-film, and shows definite anisotropy. The diffused gallium ions follow a sum of two error functions in the width and a Gaussian function in the depth direction of the channel optical thin-film. Two-dimensional gallium concentration and refractive index profiles in the channel thin-film are modeled. [ABSTRACT FROM AUTHOR]

Abstract Under 980 nm wavelength excitation, 530 and 550 nm green upconversion emission spectra of erbium-doped gadolinium gallium garnet single-crystal were measured in the temperature range of 298–423 K for ratiometric thermometry based on fluorescence intensity ratio (FIR). The crystal shows strong emission intensity, highly efficient ratiometric thermometric performance, as well as thermally stable emission spectral structure, it is thus a promising luminescent material for ratiometric thermometry. A multiple ratiometric thermometry is proposed and demonstrated in comparison with the usually adopted ratiometric thermometry based on integrated emission intensity. The multiple ratiometric thermometry considers six FIRs involving two component peaks of the 530 nm emission band and three component peaks of the 550 nm emission band, which result from an electronic transition from one Stark sublevel of the 2H 11/2 or 4S 3/2 state to another of the ground state 4I 15/2 of Er3+. All the six FIR schemes show highly efficient sensing performances with slightly different temperature characteristics. The temperature is overall determined by the six FIR schemes, largely increasing the reliability of temperature measurement. Graphical abstract We have studied ratiometric thermometry based on six fluorescence intensity ratios (FIR) involving two component peaks of 530 nm emission band and three component peaks of 550 nm emission band of erbium-doped gadolinium gallium garnet single-crystal. All the six EIR schemes display higher, slightly different relative sensitivities and thermal resolutions. The temperature is overall and reliably determined by the six EIR schemes. In addition, the crystal shows strong green upconversion emissions and thermally stable spectral structure, it is thus a promising material for the ratiometric thermometry. The multiple ratiometric thermometry based on the material has highly efficient performance, and is thus promising for reliable temperature detection in electromagnetically and/or thermally harsh environments and some industrial processes. fx1 [ABSTRACT FROM AUTHOR]

Abstract: Noncongruent nearly stoichiometric/lithium‐deficient LiTaO3 crystal was grown by lithium‐rich/lithium‐deficient chemical vapor‐phase‐equilibration (VPE) technique, and low‐cost two‐phase powder LiNbO3‐Li3NbO4 or LiNbO3‐LiNb3O8 instead of expensive LiTaO3‐Li3TaO4 or LiTaO3‐LiTa3O8 was used in the VPE experiments. The LiTaO3 crystalline phase in the lithium‐rich/lithium‐deficient crystal was confirmed by X‐ray analysis. The lithium‐rich/lithium‐deficient VPE‐induced lithium‐oxide (Li2O) molar content increase/reduction was measured as a function of VPE duration using gravimetric method, and empirical relations between them are presented for both cases. We show that both the lithium‐rich and lithium‐deficient VPE techniques based on the two‐phase powder LiNbO3‐Li3NbO4 or LiNbO3‐LiNb3O8 can be successfully used to adjust the lithium‐oxide content in a LiTaO3 crystal and produce a noncongruent nearly stoichiometric or lithium‐deficient crystal plate with desired lithium‐oxide content. [ABSTRACT FROM AUTHOR]

Under 980 nm wavelength excitation, green upconversion emission spectra of Er 3+ ions in NaYF 4 (NYF) micro-crystals were measured in the temperature range of 298–383 K. A multiple ratiometric thermometry is proposed to realize reliable temperature sensing. It considers six luminescence intensity ratios(LIRs) involving two peaks at 530 nm emission band and three peaks at 550 nm emission band, which concern electronic transitions between crystal-field Stark sublevels of Er 3+ . The six LIR schemes display similar temperature characteristics with high thermometric efficiency. The temperature can be overall determined by the six LIR schemes, largely increasing measurement reliability. The study also shows that the 980 nm excitation power adopted neither induces a detectable temperature change nor has a noticeable effect on the LIR value. In addition, the Er 3+ -doped NYF phosphor displays intense green emissions and thermally stable spectral structure which are desired for the multiple ratiometric thermometry. [ABSTRACT FROM AUTHOR]

Abstract An error in the previous paper "Electro-optic coefficients r 13 and r 33 of singly Er3+-doped and In3+/Er3+-codoped LiNbO 3 crystals" [J. Phys. Chem. Solids 100 (2017) 101–106] is corrected. The electro-optic coefficients γ 33 and γ 13 that were measured by applying a DC voltage to the crystal via the Al films coated onto the crystal surfaces are the unclamped instead of clamped coefficients. Highlights • An error in previous paper [J. Phys. Chem. Solids 100 (2017) 101] is corrected. • r 13 and r 33 were measured by two voltage-applying schemes, named A and B. • In Scheme B, a DC voltage is applied via Al films on sample surfaces. • r 13 and r 33 measured by Scheme B are unclamped instead of clamped. [ABSTRACT FROM AUTHOR]

The solubility of 1,1-diamino-2,2-dinitroethylene (FOX-7) in four binary mixed solvents (Dimethyl sulfoxide+Acetonitrile, Cyclohexanone, 1,2-Dichloroethane, Ethyl acetate) was measured by a laser dynamic method over the temperature range from 298.15 K to 333.15 K under 0.1 MPa. Experimental results showed that the solubility increases monotonously as the temperature increases at a given solvent composition or increases with the increasing of mole fraction of good solvent (Dimethyl sulfoxide) in binary mixed solvents, whereas there exists a maximum solubility value in Dimethyl sulfoxide+ Cyclohexanone system. Solubility data were well correlated by the Apelblat equation, van't Hoff equation, general single model (GSM) and modified Jouyban-Acree model, and the Apelblat equation achieved the best fitting results. Moreover, the thermodynamic properties of FOX-7 dissolution process in the investigated mixed solvents, including standard dissolution enthalpy, standard dissolution entropy and standard Gibbs free energy, were calculated by the van't Hoff and the Gibbs equations. The results demonstrate that the dissolution of FOX-7 is a non-spontaneous and endothermic process. The solubility data, correlation models, and thermodynamics properties presented in this study would provide essential support for the further research of crystallization and spheroidization of FOX-7. • The solubility data of FOX-7 was measured in four binary mixed solvents. • The experimental values were correlated and calculated by four equations. • The thermodynamic parameters (enthalpy, entropy, and Gibbs free energy) of FOX-7 were well calculated. [ABSTRACT FROM AUTHOR]