Yellow Spectral Range Research Articles

Solid-State Fiber Laser of the Yellow Spectral Range on the Rhodamine 6G Dye with an Optical Fiber Amplifier for the Formation of Sodium “Laser Guide Stars”

Solid-State Fiber Laser of the Yellow Spectral Range on the Rhodamine 6G Dye with an Optical Fiber Amplifier for the Formation of Sodium “Laser Guide Stars”

One-dimensional corner-sharing perovskites: Syntheses, structural evolutions and tunable photoluminescence properties

In recent years, organic-inorganic hybrid lead halide perovskites have emerged as a highly promising class of light emitting diodes (LEDs) due to their diverse structures and promising properties. Herein, by choosing various organic molecules as cations, we successfully constructed a series of 1D perovskites of [PMDETA]PbBr5, [PMDETA]PbCl5, [DMPZ][MA]PbBr5, [EEDA][MA]PbCl5, [EPZ][MA]PbCl5 and [EPZ]3Pb2Br10. Under the different structural directing effects of organic cations, these 1D perovskites feature three different kinds of linear or zigzag 1D [PbX5]3− chains based on purely corner-shared octahedrons. As expected, these 1D perovskites exhibit tunable broadband light emissions from blue to yellow spectral range stemming from the self-trapped excitons based on systematical characterizations including time-resolved, temperature-dependent PL emissions and theoretical calculations. This work provides crystal structural engineering for low-dimensional perovskites and paves a new way to regulate the luminescent properties.

Luminescence-site symmetry correlations in Dy3+ doped alkali-alkaline earth orthoborates of the type XZBO3 with X = Li, Na, K and Z = Mg, Ca, Ba

A systematic investigation of the luminescence properties of Dy3+ doped alkali-alkaline earth orthoborates of the stoichiometric composition XZBO3 with X = Li, Na, K and Z = Mg, Ca, Ba was conducted. XRD diffractograms show that the compounds LiMgBO3, LiCaBO3, LiBaBO3, NaMgBO3, NaCaBO3, NaBaBO3, and KMgBO3 could be produced in high purity. Relatively intense luminescence was observed only for the phases LiCaBO3, NaMgBO3, NaCaBO3 and NaBaBO3. Micro Raman investigations show that the Dy3+ luminesence mainly originates from the orthoborate phase in these samples. Photo-luminescence spectroscopy of LiCaBO3, NaCaBO3 and NaBaBO3 shows the typical Dy3+ emission with the prominent emission peak in the yellow spectral range around 575 nm. A second, but much less intense peak is observed at around 485 nm (cyan). The luminescence emission spectrum of Dy3+:NaMgBO3 is much different: here, the highest emission intensity is observed at about 485 nm. It is proposed that the Dy3+ ions occupy the Na positions in this crystal phase which has a much higher symmetry than the alkaline earth positions in the other examined crystal phases. This is supported by broadened and more split up peaks in the excitation and emission spectra of Dy3+:NaMgBO3 suggesting a much stronger local crystal field at the rare earth position in this compound. The results are additionally compared to spectroscopic data of different well known Dy3+ doped crystalline compounds and Dy3+ and Eu3+ doped alkali-alkaline earth orthoborates from other publications, which offer further insight into the relation between the crystallographic sites of the doped rare earth ions and their luminescence.

Low-threshold 1150 nm single-polarization single-frequency Yb-doped DFB fiber laser.

We demonstrate a stable single-polarization single-frequency distributed feedback Bragg (DFB) fiber laser at 1150 nm based on a 5 cm long Yb-doped fiber which, to the best of our knowledge, is the first demonstration of a Yb-doped fiber-based single-frequency laser with a wavelength longer than 1120 nm. The threshold is as low as 10 mW. The measured maximum output power is 10.6 mW, and the spectrum at the highest power shows an excellent optical signal-to-noise ratio of about 70 dB, considering the amplified spontaneous emission in a short wavelength. The polarization extinction ratio is 25 dB, and the spectral linewidth is 20 kHz. This fiber laser is suitable for seeding high-power 1150 nm narrow-linewidth laser amplifiers, which can be used as high brightness pump sources for rare-earth-doped fiber lasers and Raman fiber lasers, or to generate visible radiation in the yellow spectral range, facilitating medical and astronomic applications.

Виготовлення та дослідження властивостей бактеріальної наноцелюлози

Nanocellulose is a biopolymer that due to its attractive physicochemical properties has been intensively studied as a material for use in biomedicine, food industry, electronics etc. Modern chemical methods of nanocellulose production from wood raw materials require the use of acids, alkalis and solvents. This is a disadvantage from both economic and environmental points of view. The biomass that is obtained as a result of microbial processes can be regarded as an alternative source of nanocellulose. This paper deals with the application of the method based on Kombucha membranes for the preparation of bacterial nanocellulose. The structure and optical properties of the obtained films of bacterial nanocellulose have been studied by X-ray diffraction analysis and luminescence spectroscopy. The difference in the sizes of the regions on which X-ray scattering occurs was established from the analysis of diffraction patterns of nanocellulose films obtained by microbial and chemical methods. These regions are much larger in the case of bacterial nanocellulose. The redistribution of the peaks intensity in the diffraction patterns with a change in the manufacturing method reflects, probably, the difference in the ratio between crystalline and amorphous content for cellulose samples of various types. Samples of bacterial cellulose both "pure" and with the addition of the Rhodamine C dye are characterized by intense visible photoluminescence at room temperature. The treatment of samples with a NaOH solution leads to a decrease in the intensity of the red band (with a maximum at 670 nm) of cellulose luminescence, while the addition of a dye enhances the band in the yellow (maximum at 570 nm) spectral range. Thus, the method used in this work to made bacterial nanocellulose makes it possible to create luminescent films which emission spectra can be easily modified with alkalis or dyes treatment.

A novel approach towards crown-ether modified polyimides with affinity for alkali metal ions recognition

In the attempt to enlarge the family of imide-based materials suitable for sensor applications, novel five- and six-membered thermostable polyimides functionalized with benzo-15-crown-5 ether side chains were synthesized and thoroughly investigated with regard to their affinity for alkali metal ions recognition. For this purpose, a new diamine monomer containing as receptor triphenylmethane modified with 15-crown-5 ether (called by us crowned TPM) has been synthesized and structurally characterized. For the first time, we brought evidence for the occurrence of a ground-state intermolecular charge transfer (CT) complex between the donor crowned TPM diamine and the acceptor diimide segment which is actually responsible for the polyimides strong light emission in the green to yellow spectral range. All polyimides were electrochemically active in both anodic and cathodic regions, their voltammetric response being consistent with the coplanarity and electron accepting strength of the diimide segment. In the presence of alkali metal ions some changes appeared in the electronic absorption signals, although quite diffuse. Instead, these cations significantly altered the fluorescence response of polyimides in dependence on the excitation wavelength, cation type and polymer structure. These mostly caused the occurrence of a new emission band, when the green or yellow fluorescence turned in blue, thus proving the capability of our polyimides to detect alkali metal ions.

UV-pumped visible Tb3+-lasers.

We report on continuous-wave laser operation of Tb3+:LiLuF4 under UV pumping. More than five times higher absorption cross sections in the UV allow for shorter gain media, which are required for future high-power diode pumping. The cross-relaxation process is found to efficiently populate the upper laser level 5D4 at doping concentrations typically used in Tb3+-doped gain media. Pumping with a frequency doubled Ti:sapphire laser at 359 nm enables laser operation in the green and yellow spectral range with slope efficiencies of 41% and 20%, respectively, at optical-to-optical efficiencies a factor of two higher than under cyan-blue pumping.

Luminescence Thermometry Using Dy3+-Activated Na0.25K0.25Bi0.5TiO3 Powders

When activated by Dy3+, Na0.25K0.25Bi0.50TiO3 (NKBT), piezoelectric powders show strong luminescence in the blue and yellow spectral range. Emissions of this material can be effectively utilized for both luminescence intensity ratio and lifetime-based readouts of temperature. Photoluminescence measurements over a temperature range of 293–483 K show that the luminescence intensity ratio temperature readout has maximal relative sensitivity of 1.93% K−1 at 380 K, while the relative sensitivity of the lifetime temperature readout reaches 1.1% K−1 at 480 K. For this study, materials were synthesized by a solid-state reaction using TiO2, Bi2O3, Na2CO3, K2CO3 and Dy2O3 as precursors. X-ray diffraction measurements showed that the NKBT sample crystallized in the A-site substituted distorted perovskite rhombohedral structure (R3c symmetry). The photoluminescence spectra showed characteristic emission bands of Dy3+ ions centered at 457 nm (4I15/2 → 6H15/2), 478 nm (4F9/2 → 6H15/2), 574 nm (4F9/2 → 6H13/2) and 663 nm (4F9/2 → 6H11/2). The ratio of emissions from 4F9/2 and 4I15/2 excited states to the 6H15/2 ground state was used as a luminescence intensity ratio indicator of temperature, while the decay of emission from 4F9/2 → 6H13/2 transition was used as a lifetime indicator of temperature. CIE coordinates x = 0.326 and y = 0.361 calculated from room temperature emission spectra show the perspective of this material for use in white light emission devices.

Diode‐Pumped Laser Operation of Tb3+:LiLuF4 in the Green and Yellow Spectral Range

AbstractHere, a diode‐pumped laser based on trivalent terbium (Tb3+) as the active ion is reported. Optical pumping of a Tb3+‐doped lithium‐lutetium‐fluoride (LiLuF4) crystal with up to 200 mW from a diode laser emitting at a wavelength of 488.2 nm enables continuous‐wave lasing directly in the green and in the yellow. At an emission wavelength of 542 nm, the laser reaches an output power of up to 43.8 mW with a high slope efficiency of 52% with respect to the absorbed pump power. The yellow laser at 587 nm exhibits a slope efficiency of 22% and the output power of 13.8 mW is only limited by the available pump power. Laser thresholds as low as 14 and 27 mW of absorbed pump power are observed for the green and yellow, respectively. The investigations toward further optimization of the laser performance reveal that highly Tb3+‐doped materials are suitable for compact, efficient, and affordable diode‐pumped solid‐state lasers with direct emission in the visible spectral range. These results are of high relevance, as in particular for the yellow spectral range such systems are currently not available.

High-efficiency, yellow-light Dy3+-doped fiber laser with wavelength tuning from 568.7 to 581.9 nm.

We report, to the best of our knowledge, the first demonstration of a wavelength-tunable and highly efficient Dy3+-doped fiber laser operating in the yellow spectral region. A 2-m-long Dy3+:ZBLAN fiber pumped by a 447-nm GaN laser diode provides a strong down-conversion gain around 575nm. A fiber end-facet mirror and a visible reflective grating in the Littrow configuration construct the resonant cavity and introduce the wavelength tunability. A stable yellow laser with a <0.05-nm narrow linewidth is achieved and continuously tuned from 568.7nm to 581.9nm, covering more than half of the yellow spectral range. The slope efficiency is as high as 34.9%, and the maximum output power is 142mW at 576.44nm, which is 13 times higher than previously reported. It is, to the best of our knowledge, the highest power and conversion efficiency of a yellow-light Dy3+-doped fiber laser with wavelength tunability.

Characteristics of Amorphous As2S3 Semiconductor Films Obtained via Spin Coating

Centrifugation is used in fabricating, e.g., films with large areas and/or thicknesses of several micrometers. However, it has yet to be widely employed for chalcogenide compounds, due to their relatively weak solubility in most solvents. Determining the optimum conditions for preparing solutions of chalcogenide compounds and obtaining films via centrifugation is therefore of great interest. Specific features of amorphous arsenic sulfide (As2S3) films prepared via the centrifugation of solutions in n-butylamine have been studied. These films were characterized by means of X-ray diffraction analysis, IR spectroscopy, atomic-force microscopy and Raman spectroscopy. It was shown that amorphous As2S3 films have a greater elasticity modulus than those of analogous composition produced via thermal evaporation in vacuum, or As2S3 glass. A structural model based on arsenic sulfide clusters whose surfaces are bound by negatively and positively charged ions is used to explain the experimental results obtained in this work. DC measurements show that the amorphous films exhibit semiconductor-type conductivity. Their room temperature conductivity is ~10−15 S/cm, which indicates good dielectric properties. The films are optically transparent starting from the yellow spectral range, making them promising functional materials for engineering applications in optics and photonics.

Efficient directly emitting high-power Tb3+:LiLuF4 laser operating at 587.5 nm in the yellow range.

We present, to the best of our knowledge, the most efficient solid-state laser directly emitting in the yellow spectral range. Without any nonlinear conversion steps, a Tb3+:LiLuF4 laser operates at a wavelength of 587.5nm with an output power of 0.5W and a record-high slope efficiency of 25% with respect to the absorbed pump power at 486.2nm. Despite the detrimental influence of 4f-excited state absorption, this efficiency is comparable to those obtained by complex nonlinear methods to generate yellow laser emission. Our approach, in combination with the progress in laser diodes at the required pump wavelength, paves the way for the development of cost-efficient, robust, and easily manageable diode-pumped yellow laser sources.

Oxoberyllates SrBeO2 and Sr12 Be17 O29 as Novel Host Materials for Eu2+ Luminescence.

Beryllate structures are marginally investigated, but show intriguing structural relations to oxo- and nitridosilicates. A typical feature is the coordination of Be in both trigonal planar and tetrahedral coordination by O. A broad range of structures is accessible by variable combinations of both building units. Three novel ternary Sr-oxoberyllates are characterized by single-crystal X-ray diffraction analysis, density functional theory calculations and investigations on luminescence properties: α-SrBeO2 , β-SrBeO2 and Sr12 Be17 O29 are obtained with oxoberyllate substructures, made up of either BeO3 triangles or BeO4 tetrahedra. The compounds can be described as chain- and layer-type beryllates. When excited with blue light of (In,Ga)N LED chips, β-SrBeO2 and Sr12 Be17 O29 show visible emission in the yellow and orange spectral range, respectively, upon doping with Eu2+ . Exceptional narrow-band yellow emission (λem =564 nm, fwhm=55 nm) makes β-SrBeO2 :Eu2+ a promising phosphor for application in phosphor-converted (pc-)LEDs.

Synthesis, crystal structures, thermal, magnetic and luminescence properties of Mn(II) and Cd(II) thiocyanate coordination compounds with 4-(Boc-amino)pyridine as co-ligand

Reaction of Mn(NCS)2 and Cd(NCS)2 with 4-(Boc-amino)pyridine leads to the formation of compounds of composition M(NCS)2(4-(Boc-amino)pyridine)4 (M=Mn, 1-Mn; Cd, 1-Cd) and (M(NCS)2(4-(Boc-amino)pyridine)2 (M=Mn, 2-Mn; Cd, 2-Cd). 1-Cd and 1-Mn, respectively 2-Cd and 2-Mn are isotypic and their structures were determined by X-ray single crystal or powder diffraction. 1-Mn and 1-Cd consist of discrete complexes, whereas in 2-Mn and 2-Cd the cations are linked into chains by μ-1,3-bridging anionic ligands. On heating 1-Cd and 1-Mn, mass steps are observed that indicate formation of compounds of composition M(NCS)2(4-(Boc-amino)pyridine)2, but ex-situ XRPD investigations prove that amorphous intermediates are obtained. In contrast, temperature dependent XRPD measurements for 1-Cd indicate the formation of an unknown crystalline phase. Magnetic measurements on 2-Mn show dominating antiferromagnetic interactions along the chain and at TN=22.0K antiferromagnetic ordering is observed. 1-Cd and 2-Cd show bluish ligand-based luminescence with emission maxima at, respectively 22,301cm−1 and 20,678cm−1, while 1-Mn and 2-Mn present metal-based luminescence in the yellow spectral range with emission maxima at 18,382cm−1.

(In,Ga,Al)P–GaP laser diodes grown on high-index GaAs surfaces emitting in the green, yellow and bright red spectral range

We report on low threshold current density (<400 A cm−2) injection lasing in (AlxGa1–x)0.5In0.5P–GaAs-based diodes down to the green spectral range (<570 nm). The epitaxial structures are grown on high-index (611)A and (211)A GaAs substrates by metal–organic vapor phase epitaxy and contain tensile-strained GaP-enriched insertions aimed at reflection of the injected nonequilibrium electrons preventing their escape from the active region. Extended waveguide concept results in a vertical beam divergence with a full width at half maximum of 15° for (611)A substrates. The lasing at the wavelength of 569 nm is realized at 85 K. In an orange–red laser diode structure low threshold current density (190 A cm−2) in the orange spectral range (598 nm) is realized at 85 K. The latter devices demonstrated room temperature lasing at 628 nm at ∼2 kA cm−2 and a total power above 3 W. The red laser diodes grown on (211)A substrates demonstrated a far field characteristic for vertically multimode lasing indicating a lower optical confinement factor for the fundamental mode as compared to the devices grown on (611)A. However, as expected from previous research, the temperature stability of the threshold current and the wavelength stability were significantly higher for (211)A-grown structures.

Efficient generation of 1.9 W yellow light by cascaded frequency doubling of a distributed Bragg reflector tapered diode.

Watt-level yellow emitting lasers are interesting for medical applications, due to their high hemoglobin absorption, and for efficient detection of certain fluorophores. In this paper, we demonstrate a compact and robust diode-based laser system in the yellow spectral range. The system generates 1.9 W of single-frequency light at 562.4 nm by cascaded single-pass frequency doubling of the 1124.8 nm emission from a distributed Bragg reflector (DBR) tapered laser diode. The absence of a free-space cavity makes the system stable over a base-plate temperature range of 30 K. At the same time, the use of a laser diode enables the modulation of the pump wavelength by controlling the drive current. This is utilized to achieve a power modulation depth above 90% for the second harmonic light, with a rise time below 40 μs.

Hot injection versus room temperature synthesis of CdSe quantum dots: A differential spectroscopic and bioanalyte sensing efficacy evaluation

Abstract In this work, we have performed an exhaustive comparative study of structural, optical, and sensing properties of CdSe quantum dots (QDs) synthesized by hot-injection (HI), and room temperature (RT) protocols. CdSe QDs were synthesized in aqueous solution at room temperature by reacting cadmium chloride pentahydrate (CdCl2·5H2O) with sodium hydrogen selenide (NaHSe) in presence of capping agent 3-mercaptopropionic acid (MPA). In hot-injection (HI) method elemental Se was reacted with CdO at 225 °C. These were characterized by XRD, TEM, EDX, UV–vis, and fluorescence spectroscopy. The EDX measurements indicated that these quantum dots were highly pure, and had their composition as ≈Cd:Se = (1:1) (atomic% by weight) for both types of QD samples. These exhibited relatively narrow fluorescence band and high fluorescence intensity in the yellow spectral range. The HI-QDs exhibited high photochemical stability, and offered sufficient promise for application in design of optoelectronic devices. Steady state and time resolved fluorescence spectra revealed differential quantum yield (higher for HI-QDs), and life-times as function of synthesis protocol. However, the optical response profile revealed higher binding efficacy of RT-QDs in respect for oxalic, ascorbic acid, citric acid, and hydrogen peroxide analytes. Therefore, it is concluded that HI-QDs had rich spectroscopic signature, but poor sensing attributes (against ascorbic acid, citric acid, oxalic acid, and hydrogen peroxide) compared to RT-QDs. Further, HI-QDs could be synthesized in the size range of 2.5–6.3 nm whereas by RT method only fixed size (≈3.3 nm) nanoparticles could be prepared.

Review—Ionizing Radiation Damage Effects on GaN Devices

Gallium Nitride based high electron mobility transistors (HEMTs) are attractive for use in high power and high frequency applications, with higher breakdown voltages and two dimensional electron gas (2DEG) density compared to their GaAs counterparts. Specific applications for nitride HEMTs include air, land and satellite based communications and phased array radar. Highly efficient GaN-based blue light emitting diodes (LEDs) employ AlGaN and InGaN alloys with different compositions integrated into heterojunctions and quantum wells. The realization of these blue LEDs has led to white light sources, in which a blue LED is used to excite a phosphor material; light is then emitted in the yellow spectral range, which, combined with the blue light, appears as white. Alternatively, multiple LEDs of red, green and blue can be used together. Both of these technologies are used in high-efficiency white electroluminescent light sources. These light sources are efficient and long-lived and are therefore replacing incandescent and fluorescent lamps for general lighting purposes. Since lighting represents 20–30% of electrical energy consumption, and because GaN white light LEDs require ten times less energy than ordinary light bulbs, the use of efficient blue LEDs leads to significant energy savings. GaN-based devices are more radiation hard than their Si and GaAs counterparts due to the high bond strength in III-nitride materials. The response of GaN to radiation damage is a function of radiation type, dose and energy, as well as the carrier density, impurity content and dislocation density in the GaN. The latter can act as sinks for created defects and parameters such as the carrier removal rate due to trapping of carriers into radiation-induced defects depends on the crystal growth method used to grow the GaN layers. The growth method has a clear effect on radiation response beyond the carrier type and radiation source. We review data on the radiation resistance of AlGaN/GaN and InAlN/GaN HEMTs and GaN–based LEDs to different types of ionizing radiation, and discuss ion stopping mechanisms. The primary energy levels introduced by different forms of radiation, carrier removal rates and role of existing defects in GaN are discussed. The carrier removal rates are a function of initial carrier concentration and dose but not of dose rate or hydrogen concentration in the nitride material grown by Metal Organic Chemical Vapor Deposition. Proton and electron irradiation damage in HEMTs creates positive threshold voltage shifts due to a decrease in the two dimensional electron gas concentration resulting from electron trapping at defect sites, as well as a decrease in carrier mobility and degradation of drain current and transconductance. State-of-art simulators now provide accurate predictions for the observed changes in radiation-damaged HEMT performance. Neutron irradiation creates more extended damage regions and at high doses leads to Fermi level pinning while 60Co γ-ray irradiation leads to much smaller changes in HEMT drain current relative to the other forms of radiation. In InGaN/GaN blue LEDs irradiated with protons at fluences near 1014 cm−2 or electrons at fluences near 1016 cm−2, both current-voltage and light output-current characteristics are degraded with increasing proton dose. The optical performance of the LEDs is more sensitive to the proton or electron irradiation than that of the corresponding electrical performances.

Laser diode pumped Nd:YAG crystals frequency summing 589 nm yellow laser

We report the efficient compact 589-nm yellow laser generation by intra-cavity sum-frequency of a continuous wave (cw) laser operation of a diode-pumped double Nd:YAG crystals at 1064nm and 1319nm. An LiB3O5 (LBO) crystal, cut for critical type I phase matching at room temperature, is used as the nonlinear optical crystals for frequency summing. A maximum output power of 102mW in the yellow spectral range at 589nm was achieved at an incident pump power of 2W. In 40min we achieved an optical-to-optical conversion efficiency of 5.1% with a power instability less than 5.66%, the configuration is compact, flexible and efficient.

Narrow-Band Green Emitting Nitridolithoalumosilicate Ba[Li2(Al2Si2)N6]:Eu2+ with Framework Topology whj for LED/LCD-Backlighting Applications

Eu2+- as well as Ce3+-doped Ba[Li2(Al2Si2)N6] and its related Mg-substituted compounds Ba[(Mg2–xLix) (Al4–xSix)N6]:Eu2+ (x = 0–2) with x = 1.6, 1.8 have been synthesized by metathesis reactions in tantalum ampules. Crystal structures were solved and refined from single-crystal X-ray diffraction data. All three compounds crystallize in tetragonal space group P4/ncc (no. 130) (Z = 4, Ba[Li2(Al2Si2)N6]:Eu2+: a = 7.8282(4), c = 9.9557(5) A, R1 = 0.0144, wR2 = 0.0366). Their crystal structures, exhibiting the novel framework topology whj, consist of a highly condensed anionic tetrahedra network of disordered (Li/Mg)N4 and (Al/Si)N4 units connected to each other by common edges and corners. The degree of condensation (i.e., atomic ratio (Al,Li,Mg,Si):N) is κ = 1. The Ba2+-position is coordinated eight-fold by N3– in form of a truncated square pyramid. Upon doping with Eu2+, narrow-band emission in the green to yellow spectral range is observed (λem = 532–562 nm, fwhm ≈ 1962 cm–1). Ce3+-doped crystals of Ba[Li2(...