Broad Near-infrared Emission Research Articles

Role of Ni2+(d8) ions in electrical, optical and magnetic properties of CdS nanowires for optoelectronic and spintronic applications

For the first time, 1D Ni ion doped CdS nanowires (NWs) were synthesized via chemical vapour deposition (CVD). The synthesized Cd0.886Ni0.114S NWs were single crystalline. We have reported here the investigation of optical, electrical and magnetic properties of prepared NWs for optoelectronic and spintronic applications. Successful incorporation of Ni ions in an individual CdS NW has been confirmed through several characterization tools: significantly higher angle and phonon mode shift were observed in the XRD and Raman spectra. SEM-EDX and XPS analysis also confirmed the presence of Ni2+ ions. Room temperature photoluminescence (RT-PL) showed multiple peaks: two emission peaks in the visible region centered at 517.1 nm (green), 579.2 nm (orange), and a broad-band near infra-red (NIR) emission centered at 759.9 nm. The first peak showed 5 nm red shift upon Ni2+ doping, hinting at the formation of exciton magnetic polarons (EMPs), and broad NIR emission was observed in both chlorides and bromides, which was assigned to d−d transition of Ni ions whose energy levels lying at 749.51 nm (13 342 cm–1) and 750.98 nm (13 316 cm–1) are very close to NIR emission. Orange emission not only remained at same peak position—its PL intensity was also significantly enhanced at 78 K; this was assigned to d−d transition (3A2g → 1Eg) of Ni2+ ions. It was observed that 11.4% Ni2+ ion doping enhanced the conductivity of our sample around 20 times, and saturation magnetization (Ms) increased from 7.2 × 10−5 Am2/Kg to 1.17 × 10−4 Am2/Kg, which shows promise for optoelectronic and spintronic applications.

Formation, element-migration and broadband luminescence in quantum dot-doped glass fibers.

All solid-state PbS quantum dot (QD)-doped glass precursor fibers avoiding crystallization during fiber-drawing process are successfully fabricated by melt-in-tube technique. By subsequent heat treatment schedule, controllable crystallization of PbS QDs can be obtained in the glass precursor fibers, contributing to broad near-infrared emissions from PbS QD-doped glass fibers. Nevertheless, we find that element-migration and volatilization of sulfur simultaneously happen during the whole fiber-drawing process, because of the huge difference between the melting temperature of core glass and the fiber-drawing temperature. Element-migration pathways along the fiber length were revealed. Such PbS QD-doped glass fiber with broadband emissions will be a potential application as gain medium of broadband fiber amplifiers and fiber lasers.

Quantum cutting and tunable luminescence properties in Pr3+/Sm3+, Yb3+ co-doped SrMoO4 powders

Pr3+, Yb3+ and Sm3+, Yb3+ co-doped SrMoO4 phosphors have been prepared via high temperature solid-state reaction method. The quantum cutting based on Sm3+,Yb3+ couple results in a new emission band at 1000nm and the quantum cutting based on Pr3+,Yb3+ couple realizes a broad near-infrared emission of about 76nm in full width at half maximum, centered at 1000nm. Meanwhile the near infrared emission intensity for Sm3+, Yb3+ and Pr3+, Yb3+ co-doped SrMoO4 phosphors have also been increased by 2.1 and 1.8 times, with 36.5% and 9.6% energy transfer efficiencies from Sm3+ to Yb3+ and Pr3+ to Yb3+, respectively. The result provides a meaningful reference for designing broad-band near infrared phosphors or tunable near infrared laser materials.

Synthesis and Photoluminescence Properties of SrLaAlO<sub>4</sub>: Ti Green-Emitting Phosphor

Ti-doped SrLaAlO4 green-emitting phosphor was synthesized via solid-state reactions in air and N2 atmosphere. Sample heated in air showed no emission, however, sample heated in N2 showed broad green emission around 492 nm and broad near-infrared emission around 950 nm by 321 nm near-ultraviolet excitation. XPS measurement and UV-Vis diffuse reflectance spectra suggest that Ti in the sample was reduced to Ti3+ state when the sample was heated in N2. Possible emission mechanism of the sample can be explained as O2-–Ti3+ charge-transfer transition.

Improved Near-Infrared Up-Conversion Emission of Tm3+ Sensitized by Yb3+ and Ho3+ in LuF3 Nanocrystals.

In the present work, mono-disperse and uniform orthorhombic lutetium fluoride (LuF3) nanocrystals with an average size of about 35 nm have been successfully synthesized by a simple ionothermal method without any template. The infrared (IR) to visible up-conversion (UC) photoluminescence of LuF3 doped with Yb3+, Tm3+, and Ho3+ under 980 nm excitation was systemically studied. The intensity of near infrared (NIR) to visible up-conversion emission of Tm3+ was improved efficiently by adding Yb3+ and Ho3+ in LuF3, especially for the broad NIR emission band located at 812 nm. Meanwhile, compared to the Yb3+ and Tm3+ co-doped LuF3, the ratio of red to green emission in the Yb3+, TmS+, and HoS+ co-doped LuF3 changed greatly, and a bright yellowish-green emission was observed under 980 nm laser excitation. It shows that Yb3+, Tm3+ and Ho3+ co-doped LuF3 nanocrystals provided a potential application in vitro and in vivo bio-imaging, color displays and optical storage.

Yb3+/Tm3+/Ho3+ tri-doped silica-based glass: intense up-conversion and broad near-infrared emission

The Yb3+/Tm3+/Ho3+ tri-doped silica-based glasses are firstly prepared by the CO2 laser sintering method. The up-conversion (UC) luminescence and near-infrared emission properties are investigated under 980 nm excitation. Broad emission band with the full width at half maximum of 400 nm within the infrared spectral region around 2 μm is obtained. In addition, the energy transfer mechanism among Yb3+, Tm3+, and Ho3+ are discussed in detail. The experimental results show that the Yb/Tm/Ho tri-doped silica-based glasses prepared by the CO2 laser sintering method can be the potential materials for white light source and infrared laser operating at 2 μm.

Li2SrSiO4:Ce3+, Pr3+ Phosphor with Blue, Red, and Near‐Infrared Emissions Used for Plant Growth LED

Ce3+/Pr3+ codoped Li2SrSiO4 (LSS) phosphors with blue, red, and near‐infrared (NIR) tri‐emission have been prepared via a high‐temperature solid‐state reaction method. Under the excitation of 200 to 400 nm near‐ultraviolet (n‐UV), the photoluminescence (PL) spectra of phosphors are composed of visible and NIR two parts. The former exhibits blue and red emission bands centered at around 428 nm from 5d–4f transition of Ce3+ and 611 nm from 1D2 → 3H4 transition of Pr3+, those overlap with photosynthesis action spectra of plants and absorption spectra of chlorophylls and carotenoids. While the later presents a broad NIR emission band peaking near 1039 nm caused by the 1G4 → 3H4 of Pr3+, matching with the absorption of bacteriochlorophyll. Their emission intensity ratios (B: R: NIR) could be tuned by altering the relative ratios of Ce3+ and Pr3+ concentration in the phosphors to meet the requirements of multifarious plants and bacteria. The efficient energy transfer from Ce3+ to Pr3+ takes place in the LSS host, which ascribed to an exchange interaction according to PL spectra and decay curves of phosphors. Results suggest that the present LSS: Ce3+, Pr3+ phosphors have great potential applications in plant growth n‐UV LED.

Near Infrared Emission Band and Origin in Ni(II)-Doped CdS Nanoribbons by CVD Technique

In this work, we report the synthesis of high-quality Ni-doped CdS nanoribbons via chemical vapor deposition (CVD) method. The as-synthesized samples were characterized by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) techniques. The presence of Ni ions in CdS nanoribbons has been confirmed through energy-dispersive X-ray spectroscopy (EDX) and nonuniform peak shifting of Raman spectrum. Except the bandedge emission, the photoluminescence (PL) properties of Ni-doped CdS nanoribbons are dominated by a broad near-infrared (IR) emission band centered around 1.61 eV. This transition corresponds to two high levels of d electronic state of Ni with strong p-d hybridization between Ni ions and S, which seldom happens in usual dilute magnetic semiconductors (DMS). The p-d hybridization is confirmed by the simulation of electronic band structure in Ni-doped CdS wires with first-principle calculation and PL lifetime measurements, which blocked the optical transitions of lowest d le...

Structural and optical properties of Er3 +-Yb3 + codoped multicomposition TeO2-ZnO-PbO-TiO2-Na2O glass

We investigate the structural and spectroscopic properties of multicomposition Er3+-Yb3+ codoped TeO2-ZnO-PbO-TiO2-Na2O glass. Both structural and thermal studies have been performed via X-ray diffraction and differential scanning calorimetry respectively in order to verify its glassy nature. The Raman spectroscopy has revealed the glass network consists of [TeO4], [TeO3+1] and [TeO3] groups as basic structural units. Optical absorption measurements have been carried out and analyzed by Judd–Ofelt and McCumber theories where important spectroscopic parameters such as intensity parameters Ωt (t=2, 4, 6) transition probabilities, and stimulated emission cross section at 1.5μm are calculated. Broad near-infrared emission at 1564 with full width at half maximum around 70nm were obtained under 980nm laser excitation.

Integrated broadband near-infrared luminescence in transparent glass ceramics containing γ-Ga2O3: Ni2+ and β-YF3: Er3+ nanocrystals

Ni2+/Er3+ dual-doped transparent glass ceramic containing γ-Ga2O3 and β-YF3 nanocrystals is prepared by melt quenching and subsequent heating. It is experimentally demonstrated that Ni2+ and Er3+ are partitioned into γ-Ga2O3 and β-YF3 nanocrystals, respectively, which greatly reduces the adverse energy transfer between them. Accordingly, an integrated broad near-infrared emission band in the wavelength region of 1020–1650nm, consisting of Ni2+: 3T2(F)→3A2(F) emission around 1220nm and Er3+: 4I13/2→4I15/2 emission around 1540nm, is observed under 980nm excitation. Compared to that in the Ni2+/Er3+ dual-doped glass ceramic containing γ-Ga2O3 and LaF3 nanocrystals, the integrated near-infrared emission intensity in the present sample is increased by two times, ascribing to the higher Er3+ solubility in β-YF3 crystallites.

Direct radiative recombination in the Se-terminated nanoscale Si porous structure

We prepared vertical porous silicon nanowire (SiNW) arrays using the silver-assisted electroless etching method. The post-selenization treatment was carried out to passivate the surface of the nanostructure with Se-related bonds. Besides the great enhancement of the photoluminescence (PL) intensity and stability, the slow red emission band from the untreated porous SiNWs disappears and the new PL bands blue-shift to the higher energy, with the recombination rate more than three orders of magnitudes faster than that of the red emission band. The lifetime of 0.49 and 2.68ns are attributed to the recombination in the Si nanostructures passivated with SiSe, and SiSeO bonds, respectively. The fast recombination rates indicate that surface modification induced by selenization treatment could lead to the direct radiative recombination of Si nanostructure. Furthermore, a broad near-infrared emission band located at around ∼1300nm is also observed. These results are thought useful in the band gap engineering of Si.

Experimental and theoretical studies of photoluminescence from Bi82+ and Bi53+ stabilized by [AlCl4]− in molecular crystals

The photophysical properties of Bi82+ and Bi53+ polycations stabilized by [AlCl4]- have been studied experimentally and theoretically. The obtained product was thoroughly evaluated by powder X-ray diffraction and photoluminescence spectroscopy, making it clear that both Bi82+ and Bi53+ contribute to the observed broad near-infrared emission. Furthermore, it was revealed that Bi82+ polycation mainly results in the emission peaking at ca. 1180 nm, while Bi53+ the longer-wavelength emission. The following quantum chemistry calculation on Bi82+ polycation helps us attribute some observed excitation bands in the visible spectral range to specific electronic transitions of bismuth polycations. It is believed that systematical investigation of structural and luminescent properties as well as detailed quantum chemistry calculation of molecular crystals containing such kinds of bismuth units allows us to obtain a clearer picture on bismuth-related photophysical behaviors, which not only serve to solve the confusions on the luminescence origin of bismuth in other material systems such as bulk glasses, glass fibers and conventional crystals, but also is helpful to develop novel applicable broadband tunable laser mediums.

Spectroscopic investigations of Nd3+-, Er3+-, Er3+/Yb3+-, and Tm3+-ions doped SiO2–Al2O3–CaF2–GdF3 glasses

Abstract This paper reports on the absorption, visible and near-infrared luminescence properties of Nd3+, Er3+, Er3+/2Yb3+, and Tm3+ doped oxyfluoride aluminosilicate glasses. From the measured absorption spectra, Judd–Ofelt (J–O) intensity parameters (Ω2, Ω4 and Ω6) have been calculated for all the studied ions. Decay lifetime curves were measured for the visible emissions of Er3+ (558 nm, green), and Tm3+ (650 and 795 nm), respectively. The near infrared emission spectrum of Nd3+ doped glass has shown full width at half maximum (FWHM) around 45 nm (for the 4F3/2→4I9/2 transition), 45 nm (for the 4F3/2→4I11/2 transition), and 60 nm (for the 4F3/2→4I13/2 transition), respectively, with 800 nm laser diode (LD) excitation. For Er3+, and Er3+/2Yb3+ co-doped glasses, the characteristic near infrared emission bands were spectrally centered at 1532 and 1544 nm, respectively, with 980 nm laser diode excitation, exhibiting full width at half maximum around 50 and 90 nm for the erbium 4I13/2→4I15/2 transition. The measured maximum decay times of 4I13/2→4I15/2 transition (at wavelength 1532 and 1544 nm) are about 5.280 and 5.719 ms for 1Er3+ and 1Er3+/2Yb3+ (mol%) co-doped glasses, respectively. The maximum stimulated emission cross sections for 4I13/2→4I15/2 transition of Er3+ and Er3+/Yb3+ are 10.81×10−21 and 5.723×10–21 cm2. These glasses with better thermal stability, bright visible emissions and broad near-infrared emissions should have potential applications in broadly tunable laser sources, interesting optical luminescent materials and broadband optical amplification at low-loss telecommunication windows.

Spectral analysis of RE3+ (RE = Er, Nd, Prand Ho):GeO2–B2O3–ZnO–LiF glasses

This paper reports on the absorption, visible and near-infrared luminescence properties ofEr3+,Nd3+,Pr3+ and Ho3+-doped alkali fluoride zinc boro germanate glasses. The x-ray diffraction(XRD) and differential thermal analysis (DTA) profiles of the host glasshave been carried out, to confirm its structure and thermal stability. Fromthe measured absorption spectra, Judd–Ofelt (JO) intensity parameters(Ω2,Ω4 and Ω6) have been calculated for all the studied ions. ForPr3+ and Ho3+-doped glasses, upconversion emission spectra have also beenmeasured. Decay curves were measured for the visible emissions ofEr3+,Pr3+ andHo3+ ions at 547 nm(Er3+: green), 604 nm and641 nm (Pr3+: orange andred) and 658 nm (Ho3+: red), respectively. The near-infrared emission spectra ofEr3+/Yb3+ and Nd3+-doped glasses have shown full width at half maximum (FWHM) around 95 nm (for the transition) and 63 nm (for the transition), respectively. The measured maximum decay times of transition (at wavelength 1.51 µm) are about 5.72 ms and 6.14 ms for1.0Er3+ and 1.0Er3+/ 2Yb3+ (mol%)-codoped glasses, respectively. The maximum stimulated emission crosssections for transition of Er3+ and Er3+/Yb3+ are 5.447 × 10−21 cm2 and 4.540 × 10−21 cm2. These glasses with better thermal stability, bright visible emissions and broadnear-infrared emissions should have potential applications in broadly tunable laser sources,interesting optical luminescent materials and broadband optical amplification in low-losstelecommunication windows.

Spectral analysis of Er3+-, Er3+/Yb3+- and Er3+/Tm3+/Yb3+-doped TeO2–ZnO–WO3–TiO2–Na2O glasses

In this paper, we present the spectroscopic properties ofEr3+-,Er3+/Yb3+- andEr3+/Tm3+/Yb3+-dopednovel tellurite glasses. From the measured absorption spectra, Judd–Ofelt (JO) intensity parameters(Ω2,Ω4 andΩ6) have beenevaluated for the Er3+-doped glass. With 980 nm excitation three strong upconversionemission bands centered at 505, 520 and 630 nm were observed for bothEr3+- andEr3+/Yb3+-codoped glasses and the characteristic near-infrared emission bands were spectrally centered at1.535 µm. Thenear-infrared spectra of Er3+- and Er3+/Yb3+-doped glasses have shown full width at half-maxima (FWHM) around 100 nm and 120 nmfor the erbium transition, respectively. The measured maximum decay times of the transition (at wavelength1.535 µm) are about7.24 ms and 7.68 ms for 1.0Er3+ and 1.0Er3+/ 2Yb3+ (mol%)-codoped glasses, respectively. The maximum stimulated emission cross sectionsfor the transition of Er3+ and Er3+/Yb3+ are 8.64 × 10−21 and 6.78 × 10−21 cm2.From 1Er3+/ 1Tm3+/ 2Yb3+ (mol%)-codoped glass, broad near-infrared emission bands centered at 1510 nm () and 1637 nm () with full width at half-maxima (FWHM) around 52 nm and 60 nm, respectively, wereobserved. These glasses with broad near-infrared emissions should have potentialapplications in tunable lasers and broadband optical amplification at low-losstelecommunication windows

NIR luminescence from Er 3+/Yb 3+, Tm 3+/Yb 3+, Er 3+/Tm 3+ and Nd 3+ ions-doped zincborotellurite glasses for optical amplification

In this paper, we report the near-infrared luminescence from the Er 3+/Yb 3+, Tm 3+/Yb 3+, Er 3+/Tm 3+ and Nd 3+ ions-doped TeO 2–ZnO–B 2O 3–Li 2O–Na 2O glasses for optical amplification. The X-ray diffraction (XRD) and differential scanning calorimetry (DSC) profiles of the host glass matrix have been carried out. From the DSC thermogram, glass transition ( T g), crystallization ( T c) and melting ( T m) temperatures have been evaluated. The near-infrared spectra of Er 3+/Yb 3+, Tm 3+/Yb 3+, Er 3+/Tm 3+ and Nd 3+ ions-doped glasses have shown full-width at half-maxima (FWHM) around 58, 127, 87 and 35 nm, respectively. These glasses with better thermal stability and broad near-infrared emissions should have potential applications in broadly tunable laser sources and broadband optical amplification at low-loss telecommunication windows.

Broadband near-infrared emission from Tm3+∕Er3+ co-doped nanostructured glass ceramics

Transparent SiO2-Al2O3-NaF-YF3 glass ceramics co-doped with Er3+ and Tm3+ were prepared by melt quenching and subsequent heating. X-ray diffraction and transmission electron microscopy experiments revealed that β-YF3 nanocrystals incorporated with Er3+ and Tm3+ were precipitated homogeneously among the oxide glass matrix. An integrated broad near-infrared emission band in the wavelength region of 1300−1700 nm, consisting of Tm3+ emissions around 1472 nm (H34→F34) and 1626 nm (F34→H36), and Er3+ emission around 1543 nm (I413∕2→I415∕2), was obtained under 792 nm laser excitation. The full width at half maximum of this integrated band increased with the increasing of [Tm]/[Er] ratio, and it reached as large as 175 nm for the 0.1 mol% Er3+ and 0.8 mol% Tm3+ co-doped sample. The energy transfers between Er3+ and Tm3+ were proposed to play an important role in tailoring the emission bandwidth of the sample.

Ultrabroadband near-infrared emission from Bi-doped Li2O–Al2O3–SiO2 glass

A broad near-infrared emission of Bi-doped lithium alumino silicate glasses has been investigated. It was found that the peak wavelength and width of the emission from the glasses could be controlled drastically by the excitation wavelength. The emission spectrum had the broadest bandwidth of more than 500nm under 900nm excitation. The emission consisted of two Gaussian peaks and the stimulated emission cross sections at the peaks were calculated as 7.3×10−21 and 2.3×10−20cm2. The lifetime was almost independent of temperature up to 350K, indicating that the emission from the Bi-doped lithium alumino silicate glass has strong resistance to the thermal quenching.

Light emission from silicon-rich nitride nanostructures

Light-emitting Si-rich silicon nitride (SRN) films were fabricated by plasma enhanced chemical vapor deposition followed by low temperature (500–900°C) annealing. The optical properties of SRN films were studied by micro-Raman and photoluminescence spectroscopy and indicate the presence of small Si clusters characterized by broad near-infrared emission, large absorption/emission Stokes shift, and nanosecond recombination. Our results are supported by first-principles simulations indicating that N atoms bonded to the surface of nanometer Si clusters play a crucial role in the emission mechanism of SRN films. Light emission from SRN systems can provide alternative routes towards the fabrication of optically active Si devices.

X-ray-Underluminous Active Galactic Nuclei Relative to Broad Emission Lines in Ultraluminous Infrared Galaxies

We present X-ray spectra of four ultraluminous infrared galaxies (ULIRGs) with detectable broad near-infrared emission lines produced by active galactic nuclei (AGNs): Mrk 463, PKS 1345+12, IRAS 05189-2524, and IRAS 07598+6508. With the exception of IRAS 07598+6508, high-quality X-ray spectra obtained with XMM or Chandra show modest (30–340 eV) equivalent widths of the 6.4 keV Fe Kα emission line and clear signatures for absorption at a level of 4–33 × 1022 cm-2 for the main power-law components from the AGNs. These spectral properties are typical of Compton-thin AGNs, and so we estimate absorption-corrected 2–10 keV X-ray luminosities for the AGNs, LX(2–10 keV) using the Compton-thin assumption. We compare the LX(2–10 keV) values with broad optical/near-infrared emission-line luminosities and confirm a previous finding by Imanishi &Ueno that the LX(2–10 keV) to broad emission-line luminosity ratios in ULIRGs are systematically lower than those of moderately infrared-luminous type 1 AGNs. A comparison of independent energy diagnostic methods suggests that the AGNs are underluminous in the 2–10 keV band with respect to their overall spectral energy distributions, as opposed to the broad emission lines being overluminous. This X-ray underluminosity should be taken into account when using 2–10 keV X-ray data to investigate the energetic contribution from AGNs to the large infrared luminosities of ULIRGs.