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Efficient broadband near-infrared emission based on copper-alloyed metal halides

Recently, metal halides have shown broad application prospects due to excellent electronic and optical properties. Although significant developments have been realized, the spectra range of their photoluminescence (PL) emission is mainly limited to the visible region. Near-infrared (NIR) emitting materials are widely used in the fields of night vision, biomedical imaging, non-destructive food inspection, etc. On this occasion, extending the luminescence scope of metal halides to NIR region is of great significance. Generally, NIR-emitted metal halides are realized through rare earth (RE) ions doping. However, RE luminescence usually have narrow-band characteristics, which makes it difficult to realize broadband NIR emission. In this study, we present an efficient broadband NIR-emitted metal halide CsAgBr2 through copper ions alloying, its emission locates at 830 nm with a large FWHM (full width at half maximum) of 332 nm. Theoretical calculations suggest that the incorporation of Cu+ could effectively modulate the density of states and enhance the localized characterization, which is beneficial to boost the PL efficiency. Furthermore, this material displays favorable structure stability under ambient conditions. This study demonstrates the great application potential of Cu+-alloyed CsAgBr2 in the field of NIR optical electronics.

Highly efficient blue-light-excitable ultra-broadband orange-emitting Mg2.5Y1.5Al1.5Si2.5O12:Ce3+ garnet phosphors for solid-state lighting

Lighting and display technologies are revolutionized by the invention of YAG:Ce3+ phosphors driven by InGaN blue light-emitting diode (LED). Yet, the faint emission components in the red spectral region from typical LED devices can cause circadian rhythm disorders and aesthetic fatigue of the human eye. Developing broadband orange-emitting phosphor with abundant red coverage is one of the approaches for addressing this challenging problem. Herein, an innovative ultra-broadband orange-emitting Mg2.5Y1.5Al1.5Si2.5O12:Ce3+ (MYASO:Ce3+) garnet phosphor is successfully reported to bridge the above gap. The representative MYASO:4%Ce3+ sample exhibits an unexpectedly luminescence band with the full width at half maximum (FWHM) of up to 155 nm, the high thermal robustness (58%@423 K), and satisfactory internal quantum efficiency of 67% upon 465 nm blue light excitation. Such a large FWHM value results from the occupation of a single crystallographic site of Ce3+ in the dodecahedral [YO8] position of MYASO garnet host. Red-shift emission with respect to commercial YAG:Ce3+ is mainly attributed to the cooperative effect of the enhanced crystal field strength and increased Stokes shift. The emission intensity reduction at the high-temperature environment of MYASO:4%Ce3+ is derived from the enhancement of the thermal cross-relaxation associated with the larger Stokes shift (4839 cm−1). The resulting high-quality warm white LED device fabricated from the optimal MYASO:4%Ce3+ sample shows a satisfactory color rendering index (CRI = 84), comfortable correlated color temperature (CCT = 4032 K) and an excellent luminous efficacy (LE = 58.7 lm W−1) under a 60 mA drive current. These findings stimulate the exploration of ultra-broadband orange-emitting phosphors with abundant red emission to fabricate high-CRI warm-white LEDs for healthy solid-state lighting.

From Sub-Solar to Super-Solar Chemical Abundances along the Quasar Main Sequence

The 4D (four-dimensional) eigenvector 1 (E1) sequence has proven to be a highly effective tool for organizing observational and physical properties of type-1 active galactic nuclei (AGNs). In this paper, we present multiple measurements of metallicity for the broad line region gas, from new and previously-published data. We demonstrate a consistent trend along the optical plane of the E1 (also known as the quasar main sequence), defined by the line width of Balmer hydrogen Hβ profile and by a parameter measuring the prominence of singly-ionized iron emission. The trend involves an increase from sub-solar metallicity in correspondence with extreme Population B (weak Feii emission, large Hβ FWHM (full width at half maximum)) to metallicity several tens the solar value in correspondence with extreme Population A (strongest Feii optical emission, narrower Hβ profiles). The data establish the metallicity as a correlate of the 4DE1/main sequence. If the considerably high metallicity (Z≳10Z⊙, solar metallicity) gas is expelled from the sphere of influence of the central black hole, as indicated by the widespread evidence of nuclear outflows and disk wind in the case of sources radiating at a high Eddington ratio, then it is possible that the outflows from quasars played a role in chemically enriching the host galaxy.

The growth and spectroscopic properties of Yb:KNGM crystal: A promising ultrashort pulse laser material

Yb3+-doped mixed laser crystals are widely recognized as materials capable of generating ultrashort pulses and have garnered significant attention in recent times. In this study, we thoroughly examined the structure and spectroscopic properties of a novel mixed molybdate crystal, Yb:KNGM. Notably, we made detailed observations of an exceptionally broad absorption band with a full width at half maximum (FWHM) of 78 nm. The broad absorption band indicates that the commercially available InGaAs laser diode (LD) can be effectively utilized for high pumping efficiency purpose. The absorption and emission cross-section at 967 and 1014 nm were calculated to be 1.56 × 10−20 cm2 and 2.05 × 10−20 cm2, respectively. The FWHM of the emission band reaches a substantial range of 62 nm, making it highly conducive to the production of ultrashort pulse lasers. The bandgap (Eg) was fitted as 3.26 eV by Tauc formula. Positive gain cross-section can be achieved while the β is only higher than 0.2 and a large FWHM of 41 nm was discovered when β is 0.5. The aforementioned merits provide compelling evidence that Yb:KNGM crystal holds great promise as a laser crystal for the application of wild tunable and ultrashort pulse lasers pumped by LD.

Numerical Simulation of Rapid Nitriding of Aluminum via Pulsed Laser

To better understand the mechanisms of pulsed laser-assisted synthesis of metal nitride, a numerical model was proposed to simulate the process of laser nitriding of aluminum. The model incorporated various multiphysical processes in the laser nitriding process, including heating, melting and vaporization of aluminum, formation of plasma plume, shielding of laser energy, ionization of nitrogen gas, and the transport of nitrogen in the chemically active state N* (N atoms and N+ ions) inside the aluminum. The simulated results are in good agreement with the existing experimental results in terms of laser intensity, laser impulse, N+ lifetime in plume, and nitrogen diffusion depth in aluminum. The model can well simulate the laser shielding process by plume and the nitriding process of aluminum. Characteristics of the plume expansion, plasma formation, nitrogen ionization, and diffusion were investigated systematically by the developed model. Investigations on the effects of key operating conditions show that the impact of laser wavelength is negligible, while the full-width at half-maximum (FWHM), nitrogen gas pressure, and laser intensity have a significant impact on the laser nitriding process of aluminum. The larger FWHM and larger laser intensity yield a layer with a higher N* concentration and greater thickness. The higher nitrogen gas pressure leads to an increase in N* concentration at the same position.

Achievement of broadband NIR emission in double perovskite NaLaMgWO6 via non-equivalent substitution of Cr3+

Low-cost and high-efficient broadband near-infrared (NIR) phosphor converted light-emitting diodes (pc-LEDs) are desirable for the compact NIR spectrum system. In this work, a broadband NIR emission with a large full width at half maximum (FWHM) up to ∼160 nm is achieved in double perovskite NaLaMgWO6 phosphor via the non-equivalent substitution of Cr3+. The crystal structure analysis and first-principle calculation have revealed that Cr3+ prefers to substitute Mg2+. In order to keep charge balance, the random-distributed Na+ vacancies are formed. This behavior has constructed two different crystallographic sites for Cr3+ substitution and their effect on the NIR luminescence performances of NaLaMgWO6:Cr3+ is investigated in detail. Within the weak crystal field, the zero phonon line and broadband emissions ascribed to 4T2 → 4A2 transition are present simultaneously, which ensure the large FWHM acquired in NaLaMgWO6:Cr3+. The broadband NIR pc-LED prototype fabricated with the as-prepared phosphor and blue LED chip is achieved, which demonstrates that the NaLaMgWO6:Cr3+ is a new candidate for the broadband NIR phosphor applied in the miniaturized optical devices.

Microstructure and mechanical properties of composite strengthened high-chromium cast iron by laser quenching and laser shock peening

The study investigated the microstructure and mechanical properties of composite strengthened high-chromium cast iron by laser quenching and laser shock peening. Observation of microstructure, measurement of microhardness, residual stress and FWHM (full width at half maximum), impact toughness and wear tests were carried out on untreated, laser quenched, laser quench-laser shock peened high-chromium cast iron specimens. The research results showed that the laser shock peening will not produce new phases in high-chromium cast iron, and can further promote the transformation of retained austenite into martensite. The grains inside the laser quench-laser shock peened sample were obviously refined, and the carbides were uniformly dispersed. The laser quench-laser shock peened specimen produced large residual compressive stress and FWHM value on the surface, reaching −432.49 MPa and 2.124°, respectively. The problem of residual stress difference between the hardened zone and the transition zone caused by laser quenching was eliminated, and the tensile stress was all converted into compressive stress, which further increases the dislocation density and improves the micro-hardness. The impact toughness value of laser quench-laser shock peened specimen was 4.43 J/cm2, which was 16.27% higher than that of the untreated sample. The friction coefficient and wear rate were significantly reduced, and the wear scar was shallow and narrow, showing weak abrasive wear and oxidative wear, the impact toughness and wear resistance of high-chromium cast iron were improved. The results obtained from this study could be used as reference in future research and applications of laser strengthened high-chromium cast iron.

A systematic study of PPLN length dependence in intracavity SHG

In this paper, a systematic study of the relationship between nonlinear crystal length and intracavity second-harmonic generation (SHG) using MgO-doped periodically-poled lithium niobate (MgO:PPLN) is presented. The experimental results demonstrate a relationship between the maximum SHG power generated and the full-width at half maximum (FWHM) of the crystal’s temperature tuning curve to the length of the nonlinear optical crystal. It was shown that maximum SHG power increases rapidly with the increase of MgO:PPLN length, reaching a saturation length (~ 2 mm), which is much shorter than that predicted by the single-pass SHG theory. This saturation length of the MgO:PPLN crystal is almost independent on 808 nm pump power for typical powers used in continuous wave intracavity SHG lasers. In addition to this saturation effect, a broadening effect was also observed, the FWHM of the temperature tuning curve was shown to have a larger FWHM than that predicted by the single-pass SHG theory for MgO:PPLN shorter than the saturation length. This work has the benefit of allowing engineers to optimize nonlinear crystal length when developing intracavity SHG based diode-pumped solid state (DPSS) lasers.

Broadband near-infrared emission of K3ScF6:Cr3+ phosphors for night vision imaging system sources

• K 3 ScF 6 :Cr 3+ can be excited by blue light, leading to a broadband NIR emission. • K 3 ScF 6 :Cr 3+ retain 87.3% of their initial emission intensity at 150 °C. • The fabricated NIR-LED based on K 3 ScF 6 :Cr 3+ has good photoelectric efficiency. • NIR-LED based on K 3 ScF 6 :Cr 3+ can be applied in night vision imaging systems. Broadband near-infrared light (NIR) near 800 nm has broad application prospects in food detection and night vision monitoring. Compared with NIR chips, NIR phosphors have distinct advantages, including low cost, a mature synthesis process, and tunable combination. However, at present, oxide NIR phosphors have some disadvantages, such as a narrow full width at half maximum (FWHM), poor thermal stability, and low photoelectric efficiency. Herein, K 3 ScF 6 :Cr 3+ NIR phosphors with a cubic structure were synthesized using the hydrothermal method. These phosphors can be effectively excited by blue light (430 nm) and red light (630 nm), leading to a broadband Cr 3+ emission from 650 nm to 950 nm with a large FWHM of 430 nm. They also exhibit excellent thermal stability and retain 87.3% of their initial intensity at 150 °C. Under a driving current of 100 mA, their photoelectric efficiency can reach 9.315% of that of fabricated NIR light-emitting diodes (NIR-LED). An NIR-LED device based on this phosphor can thus be implemented in night vision imaging systems.

Delta-doped β -Ga2O3 films with narrow FWHM grown by metalorganic vapor-phase epitaxy

We report on the low-temperature metalorganic vapor-phase epitaxy (MOVPE) growth of silicon delta-doped β-Ga2O3 films with a low full width at half maximum (FWHM). The as-grown films are characterized using secondary-ion mass spectroscopy, capacitance–voltage, and Hall techniques. Secondary ion mass spectroscopy measurements show that surface segregation is the chief cause of a large FWHM in MOVPE-grown films. The surface segregation coefficient (R) is observed to reduce with reduction in the growth temperature. Films grown at 600 °C show an electron concentration of 9.7 × 1012 cm−2 and a FWHM of 3.2 nm. High resolution scanning/transmission electron microscopy of the epitaxial film did not reveal any observable degradation in the crystal quality of the delta sheet and surrounding regions. Hall measurements of the delta-doped film on the Fe-doped substrate showed a sheet charge density of 6.1 × 1012 cm−2 and a carrier mobility of 83 cm2/V s. Realization of sharp delta doping profiles in MOVPE-grown β-Ga2O3 is promising for high performance device applications.

Discovery of a strong ionized-gas outflow in an AKARI-selected ultra-luminous infrared galaxy at $z$ = 0.5

Abstract In order to construct a sample of ultra-luminous infrared galaxies (ULIRGs; with infrared luminosity LIR > 1012 L${_{\odot} }$) at 0.5 < $z$ < 1, we are conducting an optical follow-up program for bright 90 μm far-infrared sources with a faint optical (i < 20 mag) counterpart selected in the AKARI Far-Infrared Surveyor (FIS) Bright Source catalog (Ver.2). AKARI-FIS-V2 J0916248+073034, identified as a ULIRG at $z$ = 0.49 in the spectroscopic follow-up observation, indicates signatures of an extremely strong outflow in its emission line profiles. Its [O iii] 5007 Å emission line shows a full width at half-maximum (FWHM) of 1830 km s−1 and velocity shift of −770 km s−1 relative to the stellar absorption lines. Furthermore, the low-ionization [O ii] 3726 Å 3729 Å doublet also shows a large FWHM of 910 km s−1 and velocity shift of −380 km s−1. After the removal of an unresolved nuclear component, the long-slit spectroscopy 2D image possibly shows that the outflow extends to a radius of 4 kpc. The mass outflow and energy ejection rates are estimated to be 500 M${_{\odot} }$ yr−1 and 4 × 1044 erg s−1, respectively, which imply that the outflow is among the most powerful ones observed in ULIRGs and quasi-stellar objects at 0.3 < $z$ < 1.6. The co-existence of the strong outflow and intense star formation (star formation rate of 990 M${_{\odot} }$ yr−1) indicates that the feedback of the strong outflow has not severely affected the star-forming region of the galaxy.

Tunable near-infrared emission and fluorescent lifetime of PbSe quantum dot-doped borosilicate glass

Abstract PbSe quantum dots (QDs) were used to dope borosilicate glass with a composition of SiO 2 -B 2 O 3 -Al 2 O 3 -ZnO-AlF 3 -Na 2 O-PbO-Se, which was prepared using the conventional melt-quenching technique followed by heat treatment. We observed a broad near infrared (NIR) emission (960–1353 nm) band with a full-width-at-half-maximum (FWHM) value of 168–294 nm and a notable Stokes shift (139–167 nm), which depended on the temperature and duration of the heat treatment. At room temperature, the photoluminescence (PL) lifetime was approximately 1.24–1.92 μs, and it showed a clear dependence on the size and concentration of the QDs. The large FWHM and strong NIR emission of the PbSe QD-doped borosilicate glass may facilitate its application in NIR optical amplifiers and lasers.

Raman Spectra of Crystalline Double Calcium Orthovanadates Ca10M(VO4)7 (M = Li, K, Na) and Their Interpretation Based on Deconvolution Into Voigt Profiles

Unpolarized spontaneous Raman spectra of crystalline double calcium orthovanadates Ca10M(VO4)7 (M = Li, K, Na) in the range 150–1600 cm–1 were measured. Two vibrational bands with full-width at half-maximum (FWHM) of 37–50 cm–1 were found in the regions 150–500 and 700–1000 cm–1. The band shapes were approximated well by deconvolution into Voigt profiles. The band at 700–1000 cm–1 was stronger and deconvoluted into eight Voigt profiles. The frequencies of two strong lines were ~848 and ~862 cm–1 for Ca10Li(VO4)7; ~850 and ~866 cm–1 for Ca10Na(VO4)7; and ~844 and ~866 cm–1 for Ca10K(VO4)7. The Lorentzian width parameters of these lines in the Voigt profiles were ~5 times greater than those of the Gaussian width parameters. The FWHM of the Voigt profiles were ~18–42 cm–1. The two strongest lines had widths of 21–25 cm–1. The vibrational band at 300–500 cm–1 was ~5–6 times weaker than that at 700–1000 cm–1 and was deconvoluted into four lines with widths of 25–40 cm–1. The large FWHM of the Raman lines indicated that the crystal structures were disordered. These crystals could be of interest for Raman conversion of pico- and femtosecond laser pulses because of the intense vibrations with large FWHM in the Raman spectra.

X-ray diffraction of multi-layer graphenes: Instant measurement and determination of the number of layers

Abstract A method for determining the number of layers ( N L ) or thickness ( D GP ) of multi-layer graphene (MLG) using X-ray diffraction (XRD) is reported for the first time. The XRD pattern showed clear variations in the full-width-at-half-maximum (FWHM) values of the (0 0 2) peak of crystalline MLG with N L = 3, 4, 5, 6, and 7. The large FWHM difference per layer and the instant measurement of large areas of MLG demonstrates that XRD is a powerful probe. The obtained linear plot of FWHM versus 1/ D GP and the N L -dependent evolution of the interlayer distance ( d 002 ) toward the d 002 of graphite are also discussed.

Growth and optical properties of Co,Nd:LaMgAl11O19

Nd,Co:LaMgAl11O19 (abbreviated as Co,Nd:LMA) was grown using the Czochralski method. The structure, polarized absorption spectrum, fluorescence spectrum, and fluorescence decay time were analyzed. The as-grown crystal had very wide absorption bands at 794nm, which can be pumped by GaAs laser diode without temperature stabilization. Two strong emission bands were present at 1056nm and 1082nm with full-width at half-maximum (FWHM) of 6 and 8nm, respectively. The large FWHM is due to the inhomogeneity of the Nd ion sites. The lifetimes of the 4F3/2 manifold of Co,Nd:LMA at room temperature monitored at 905nm, 1056nm, and 1344nm were 292, 288, and 350μs, respectively, which was caused by the different contribution of the three different sites with D3h and C2v symmetry. The absorption band of Co is from 1.3μm to 1.6μm, and Co,Nd:LMA still has a strong emission around the 1.38μm, indicating that the Co,Nd:LMA can be applied as a potential self-Q-switched material operating at 1.3μm.

Effect of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline outcoupling layer on electroluminescent performances in top-emitting organic light-emitting devices

The organic compound, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) is used as a light outcoupling layer in top-emitting organic light-emitting devices with tris(8-hydroxyquinoline) aluminum emission layer. It is found that, in addition to the improvement of electroluminescent (EL) intensity and luminous efficiency with a factor of 1.6, the BCP capping layer causes a blueshift of EL spectra and a larger full width at half maximum (FWHM). A larger FWHM at the BCP capping layer of 50nm is attributed to the reduction of cathode reflectivity. In the meantime, the blueshift of EL spectra is caused by the increase of the reflective phase shift of the cathode when a thicker BCP layer is deposited. Moreover, our calculation demonstrates that the best EL coincides with a maximum magnification coefficient.

VIMOS-VLT spectroscopy of the giant Ly nebulae associated with three z 2.5 radio galaxies

The morphological and spectroscopic properties of the giant (>60 kpc) Lyα nebulae associated with three radio galaxies at z∼ 2.5 (MRC 1558–003, 2025–218 and 0140–257) have been investigated using integral field spectroscopic data obtained with the Visible Multi-Object Spectrograph (VIMOS) on VLT. The morphologies are varied. The nebula of one source has a centrally peaked, rounded appearance. In the other two objects, it consists of two spatial components. The three nebulae are aligned with the radio axis within ≲30°. The total Lyα luminosities are in the range (0.3–3.4) × 1044 erg s−1. The Lyα spectral profile shows strong variation through the nebulae, with full width at half-maximum (FWHM) values in the range ∼400–1500 km s−1 and velocity shifts Voffset∼ 120–600 km s−1. We present an infall model that can successfully explain the morphology, size, surface brightness distribution and the velocity field of the Lyα nebula associated with MRC 1558–003. It can also explain why Lyα is redshifted relative to other emission lines and the FWHM values of the non-resonant He ii line. This adds further support to our previous conclusion that the quiescent giant nebulae associated with this and other high-redshift powerful radio galaxies are in infall. A problem for this model is the difficulty to reproduce the large Lyα FWHM values, which might be the consequence of a different mechanism. We have discovered a giant (∼85 kpc) Lyα nebula associated with the radio galaxy MRC 0140–257 at z= 2.64. It shows strikingly relaxed kinematics (FWHM < 300 km s−1 and Voffset≲ 120 km s−1), unique among high-z (≳2) radio galaxies.

Universal relationship between crystallinity and irreversibility field of MgB2

The relationship between irreversibility field, Hirr, and crystallinity of MgB2 bulks including carbon substituted samples was studied. The Hirr was found to increase with an increase of full width at half maximum (FWHM) of MgB2 (110) peak, which corresponds to distortion of honeycomb boron sheet, and their universal correlation was discovered even including carbon substituted samples. Excellent Jc characteristics under high magnetic fields were observed in samples with large FWHM of (110) due to the enhanced intraband scattering and strengthened grain boundary flux pinning. The relationship between crystallinity and Hirr can explain the large variation of Hirr for MgB2 bulks, tapes, single crystals, and thin films.

Influence of initial electron beam characteristics on Monte Carlo calculated absorbed dose distributions for linear accelerator electron beams

The least known parameters in a Monte Carlo simulation of a linear accelerator treatment head are often the properties of the initial electron beam directed onto the exit vacuum window. Several initial beams with different spatial fluence distributions, angular divergences and energy spectra have been transported through the geometry of a scattering foil accelerator. The electron beam characteristics (energy spectrum and angular distribution) at the phantom surface and the subsequent relative absorbed dose distribution in a water phantom were calculated. The dose distribution was found to be insensitive to the geometrical properties of the initial beam. Furthermore, the lateral dose profiles are unaffected by the energy spectrum of the initial beam. The effect on the depth–dose curve is negligible if the initial energy spectrum is symmetric (e.g., Gaussian shaped) and its full width at half maximum (FWHM) is less than approximately 10% of the most probable energy. A larger FWHM will decrease the normalized dose gradient, but will not affect the dose in the build-up region. An asymmetric wedge shaped spectrum with a low-energy extension simultaneously increases the dose in the build-up region and decreases the dose gradient. The relationship between the energy spectral width and the normalized dose gradient is, however, smaller than published analytical expressions indicate. Some well-established energy-range relationships were shown to be accurate for most of the initial beams studied. The energy spectrum at the phantom surface was also derived from a measured depth–dose curve through different methods. The extracted spectrum depends on the beam model and the spectral reconstruction algorithm. Even though the depth–dose curve is fairly independent of initial beam characteristics, a correct description of the low-energy tail of the energy spectrum is important to obtain good agreement between measured and Monte Carlo calculated doses in the build-up region.

Determination of the crystal system and space group ofBaBiO3by convergent-beam electron diffraction and x-ray diffraction using synchrotron radiation

The crystal system and space group of ${\mathrm{BaBiO}}_{3}$ with a distorted perovskite structure were investigated by convergent-beam electron diffraction (CBED), selected area electron diffraction, and x-ray diffraction using synchrotron radiation. Since all the observed CBED patterns showed a symmetry of 1, and the $\ifmmode\pm\else\textpm\fi{}G$ dark-field disk of CBED patterns indicated the absence of an inversion center in ${\mathrm{BaBiO}}_{3},$ the crystal symmetry of ${\mathrm{BaBiO}}_{3}$ was concluded to be triclinic with a space group of $P1$ (No. 1). The diffraction angles of the x-ray-diffraction peaks of ${\mathrm{BaBiO}}_{3},$ obtained using synchrotron radiation, could apparently be explained by assuming a monoclinic symmetry. However, a larger full width at half maximum (FWHM) of the 440 peak, indexed assuming a monoclinic symmetry other than that of each peak of 008, $404\ifmmode\bar\else\textasciimacron\fi{},$ 404, and 044 could not be explained. The large FWHM of the 440 peak could be attributed to an overlapping of the $4\ifmmode\bar\else\textasciimacron\fi{}40$ and 440 peaks of triclinic symmetry, showing agreement with the result of CBED.