Emission Bandwidth Research Articles

A Review on the Ytterbium Doped Glass Laser

Abstract: A solid state laser doped with ytterbium is called a ytterbium doped glass laser. The active lasing media of solid state lasers are doped with ytterbium and other rare earth elements. Ytterbium doping produces brief pulses and increases laser efficiency. Glass lasers doped with ytterbium have an output wavelength of 1µm. The absorption capabilities and emission bandwidths are improved by ytterbium doping.[22]

Tailoring the Interfacial Composition of Heterostructure InP Quantum Dots for Efficient Electroluminescent Devices.

The formation of core-shell quantum dots (QDs) with type-I band alignment results in surface passivation, ensuring the efficient confinement of excitons for light-emitting applications. In such cases, the atomic composition at the core-shell heterojunction significantly affects the optical, and electrical properties of the QDs. However, for InP cores, shell materials are limited to compositions consisting of II-VI group elements. The restricted selection of shell materials leads to an interfacial misfit, resulting in a charge imbalance at the core-shell heterojunction. In this study, the effect of interfacial stoichiometry is investigated on the optical, and electrical properties of InP core-shell QDs. Direct Se injection strategy is employed during the synthesis of the InP core to regulate the interfacial chemical composition, resulting in the formation of an InZnSe alloy on the core surface. This InZnSe layer reduces the misfit between the InP core, and ZnSe shell, leading to a remarkable photoluminescence quantum yield of 95% with a narrow emission bandwidth of 34nm. The InZnSe interlayer significantly influences the electroluminescence (EL) processes, increasing the charge injection efficiency, and mitigating charge imbalance. A green-emitting EL device is demonstrated with a maximum luminance of 26370cd m-2, and a peak current efficiency of 31.5cd A-1.

High efficiency continuous wave and Q-switched laser based on an orthorhombic Yb:GdScO3 crystal in the (112) direction with a broad emission bandwidth of 93 nm

Herein, we demonstrate a broad emission bandwidth of 93 nm with the orthorhombic Yb:GdScO3 crystal along the (112) direction, which is about 3.7–7.8 times wider than that of cubic sesquioxide crystals. By investigating the distorted RE2Ox ligands and their association with lattice vibrations, the inhomogeneous broadening was found to be dependent on local crystal polarization and electron-phonon interaction. Moreover, the (112) direction sample has a small emission cross-section of 0.42 × 10−20 cm2 and better thermal symmetry, which allow it to achieve a continuous wave (CW) laser with a slope efficiency of 62%, a passively PdSe2 Q-switched laser with an average output power of 1.69 W, a slope efficiency of 43%, and a pulse width of 272.9 ns. We believe this to be the first investigation of the effective spectral broadening and Q-switch operations based on the orthorhombic Yb:GdScO3 crystal in the (112) direction.

Frequency conversion in a hydrogen-filled hollow-core fiber using continuous-wave fields.

In large-area quantum networks based on optical fibers, photons are the fundamental carriers of information as so-called flying qubits. They may also serve as the interconnect between different components of a hybrid architecture, which might comprise atomic and solid-state platforms operating at visible or near-infrared wavelengths, as well as optical links in the telecom band. Quantum frequency conversion is the pathway to change the color of a single photon while preserving its quantum state. Currently, nonlinear crystals are utilized for this process. However, their performance is limited by their acceptance bandwidth, tunability, polarization sensitivity, and undesired background emission. A promising alternative is based on stimulated Raman scattering (SRS) in gases. Here, we demonstrate polarization-preserving frequency conversion in a hydrogen-filled antiresonant hollow-core fiber. This approach holds promises for seamless integration into optical fiber networks and interfaces to single emitters. Disparate from related experiments that employ a pulsed pump field, we here take advantage of two coherent continuous-wave pump fields.

Effect of Lu content on microstructure and spectral properties of Yb:(LuxSc1-x)2O3 solid-solution sesquioxide transparent ceramics

Yb³⁺-doped (Lux,Sc1-x)2O3 materials demonstrate superior performance in generating short pulse lasers because of the broader emission spectra than single-component sesquioxide, making them a promising laser gain material for high-power ultrafast lasers. By adjusting the concentration of Lu/Sc, laser gain materials with different widths of emission spectra can be obtained. In this work, 5 at.% Yb:(LuxSc1-x)2O3 nano-powders with varying Lu concentrations (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9)were successfully synthesized by the co-precipitation method. Subsequently, Yb:(LuxSc1-x)2O3 transparent ceramics were produced through a combination of vacuum pre-sintering and hot isostatic pressing (HIP) post-treatment at 1700 °C. Influence of Lu content on densification process, microstructure changes and optical transmittance of Yb:(LuxSc1-x)2O3 ceramics was investigated in detail. The average grain sizes of ceramics pre-sintered at 1700 °C decrease from 3.42 μm to 1.43 μm, and all ceramics have a relatively uniform microstructure. After HIP post-treatment, the optimum in-line transmittance of Yb:(LuxSc1-x)2O3 ceramics reaches 77.6 % at 1100 nm when x value = 0.1. With the increase of Lu content, the emission wavelength experiences a gradual blueshift from 1041 nm to 1034 nm. Notably, the Yb:(Lu0.6Sc0.4)2O3 ceramics exhibited the broadest emission bandwidth of 18 nm, which is 1.5 times of the Yb:Sc2O3, suggesting their immense potential for applications in ultrashort pulse lasers.

Varying Activity and the Burst Properties of FRB 20240114A Probed with GMRT Down to 300 MHz

Repeating fast radio bursts (FRBs) can exhibit a wide range of burst repetition rates, from none to hundreds of bursts per hour. Here we report the detection and characteristics of 60 bursts from the recently discovered FRB 20240114A, observed with the upgraded Giant Metrewave Radio Telescope in the frequency ranges 300–500 MHz and 550–750 MHz. The majority of the bursts show narrow emission bandwidth with Δν/ν ∼ 10%. All of the bursts we detect are faint (<10 Jy ms) and thus probe the lower end of the energy distribution. We determine the rate function for FRB 20240114A at 400 MHz and downward drift rates at 400 and 650 MHz, and we discuss our measurements in the context of the repeating FRB population. We observe sudden variations in the burst activity of FRB 20240114A over time. From our data and the publicly available information on other observations of FRB 20240114A so far, there is an indication that FRB 20240114A potentially exhibits chromaticity in its burst activity. While the burst properties of FRB 20240114A are similar to other repeating FRBs, the frequency-dependent activity, if established, could provide crucial clues to the origin of repeating FRBs. We also place the most stringent 5σ upper limits of 600 and 89 μJy on any persistent radio source (PRS) associated with FRB 20240114A at 400 and 650 MHz, respectively, and compare these with the luminosity of the known PRSs associated with FRB 121102A and FRB 190520B.

Tuning the bandgap and photoluminescence properties of Ge/Al2O3 multilayer thin films using annealing and ion beam irradiation

Abstract The present work reports high energy ion beam irradiation induced modifications in Ge/Al2O3 multilayers (MLs). Ge and Al2O3 multilayer thin films were deposited using the electron beam evaporation technique. Afterward, the as-deposited films were annealed using Rapid thermal annealing (RTA) at different temperatures ranging from 500 to 800°C under high vacuum. At a constant fluence of 5×1012 ions /cm2, the annealed films were subjected to irradiation with 80 MeV Ag ions. X-ray diffraction patterns show the crystalline nature of films that were annealed above 500°C, and the increase in crystallite size of Ge nanocrystals from 4.5 to 5.7 nm is observed for annealed samples. After Ag ion irradiation, the crystallinity of the films deteriorates. The crystallinity and optical bandgap are found to vary with Ag ion irradiation. The band gap of annealed films decreased from 1.1 to 0.97 eV with increase in crystallite size. The band gap of irradiated samples increased than that of pristine films. In addition, photoluminescence (PL) measurements were carried out to investigate the luminescence characteristics of annealed and irradiated multilayer films, and a wide emission band in the visible region was observed. The basic mechanism for tailoring the optical band gap and PL emission using RTA and ion irradiation is discussed.&amp;#xD;&amp;#xD;

Investigation of radiation-induced luminescence properties of high-density barium phosphate glasses doped with Ce3+

The Ce3+ doped barium-zinc-gadolinium-phosphate glass samples with composition 20BaCO3-10ZnO-8Gd2O3-(62- x)P2O5-x CeBr3 (where x=0.15,0.25,0.5, and 0.75 mol.%) were fabricated by employing melt-quenching traditional method. The PXRD studies were performed to verify the amorphous form of the fabricated glasses. FE-SEM was utilised to check the particle size and shape of prepared samples. The measurements of EDS were employed to find out the elements available in the glasses. Wideband emission was observed in the 300–400 nm range in the obtained spectra under X-ray and UV–VIS excitations, revealing a 5d-4f transition of Ce3+-ions. The detected excitation bands found broad for prepared glasses include 4f electronic energy level transitions belonging to Gd3+ and the 5d electronic energy levels belonging to the Ce3+ excitation energy band situated at 308 nm. The scintillation property was investigated with α-particles and γ-rays excitations using 241Am and 137Cs, 22Na radiation sources, respectively. The lifetime of the prepared glass samples was studied under 286 nm UV excitation and found 28.94 ± 0.12 ns as a short component and 166.47 ± 23.44 ns long component with 85 % and 15 % contributions, respectively for PBZG-0.25Ce glass sample.

Fluorescence temperature dependent behaviors of Eu3+/Mn4+ co-doping cubic and hexagonal ZnO-TiO2 compounds: Application in high sensitive optical thermometers

ZnTiO3:Eu3+,Mn4+ phosphors with hexagonal and cubic structure are synthesized by solvothermal method. The structure of ZnTiO3 depends on precursors and the annealing temperature. Inverse spinel Zn2TiO4 phase reveals the highest thermostability compared with cubic ZnTiO3 and hexagonal ZnTiO3 phases. The different phases of ZnTiO3 crystals exhibit different photoluminescence properties. The forbidden transition of 4A2g→2T2g for Mn4+ is observed in Zn2TiO4 and hexagonal ZnTiO3 (h-ZnTiO3) due to the decreased symmetry. The zero photon line (ZPL) assigned to 2Eg→4A2g transition of Mn4+ is absent in all type ZnTiO3 phases. A sharp emission peak at 714 nm assigned to ν6 (Stokes emission) mode of Mn4+ in h-ZnTiO3 is present when the temperature was below 270 K, and increases sharply in intensity with the temperature decreasing. The similar PL spectra of cubic ZnTiO3 and Zn2TiO4 co-doped with Eu3+ and Mn4+ show a wide emission band composed of Stokes and anti-Stokes modes. The calculated nephelauxetic parameter increases from 0.84 to 1.03 and 1.18 for Mn4+ in h-ZnTiO3, cubic ZnTiO3 and Zn2TiO4, respectively, indicating the covalency decreasing, which causes the red shift of ZPL in h-ZnTiO3. The Mn4+ emissions show stronger temperature dependence than that of Eu3+, especially for that in h-ZnTiO3 matrix. Based on the fluorescence intensity ratio between IEu3+ and IMn4+, the highest relative temperature sensitivity of 2.46 %K−1 is observed in cubic ZnTiO3 (c-ZnTiO3) and Zn2TiO4. Under the excitation at 550 nm, the highest relative sensitivity of 2.9 %K−1 is achieved in c- and h-ZnTiO3 mixed phases.

Structure–luminescence property relationships of Yb3+-Doped Y2Mg3-xCax(SiO4)3 single crystals for 0.95–1.2 μm broadband emissions

This study successfully grew Yb3+-doped Y2Mg3-xCax(SiO4)3 (x = 0, 0.125, 0.25, 0.375, 0.5, 0.625, 0.75) (Yb: YCMS) novel single crystals with multiple disordered structures. To the best of our knowledge, this is the first systematic report on the relationship between the luminescence properties (including emission intensity, emission peak position, full width half maximum, and fluorescence lifetime) and the local structure of the luminescent ions based on first-principles calculations. The wide half-height width of emission (103.10 nm@1047 nm) have been realized on the first-grown Yb: YCMS crystals. This study provides a novel solution for designing laser crystals with tunable optical properties. The comprehensive properties of Yb3+-doped YCMS crystals, such as ultra-wide emission bandwidth and high fluorescence lifetime, are promising gain materials for ultrafast laser applications.

Manipulating photoluminescence properties of neodymium-doped fluorites through local structure regulation

The long upper level lifetimes are highly advantageous for laser diode pumped high energy laser systems. However, lifetimes of the rare earth neodymium ions, one of the most important active ions in 1 μm, are generally around 300 μs or less, which limits the development of laser diode pumped high energy lasers on neodymium gains. In this work, Nd:CaF2 and Nd:SrF2 were chosen and introduced with appropriate codopants to adjust the local structures, thereby modulating the coupling of active ions with the crystal fields. The transition rate was slowed down and a long lifetime nearly 600 μs was obtained. Neodymium-doped fluorites with broad emission bandwidths and high thermal conductivities are potential laser gains for generation of high repetition rate high power lasers.

Dual-emissive carbon dots with high-color purity from sweet basil leaves: synthesis, characterization and optical properties

Abstract In this study, we synthesized dual-emission carbon dots (CDs) from sweet basil leaves dissolved in hexane using the hydrothermal method. Extensive analyses were carried out on their morphology, structure, and optical properties. The CDs show a spherical shape and highly disordered structure with an average diameter of 2 nm. They predominantly comprise carbon surrounded by a dense shell layer of oxygen and nitrogen-related functional groups. Under excitation at a single wavelength of 380 nm, the CDs emit two distinct peaks at 450 and 675 nm demonstrating a narrow bandwidth emission with full width at half maximum (FWHM) of 72 and 27 nm, respectively. The emission characteristics of the CDs are ascribed to the combined effects of radiative recombination of the carbon-core and fully passivated surface states, resulting in two distinct emission peaks and excitation-independent emission property. We present a highly effective and eco-friendly approach approach to fabricate luminescent CDs exhibiting dual emission properties derived from sustainable resources, holding promise for utilization in bioimaging.&amp;#xD;

Purifying quantum-dot light in a coherent frequency interface

Abstract Quantum networks typically operate in the telecom wavelengths to take advantage of low-loss transmission in optical fibres. However, bright quantum dots (QDs) emitting highly indistinguishable quantum states of light, such as InGaAs QDs, often emit photons in the near infrared thus necessitating frequency conversion (FC) to the telecom band. Furthermore, the signal quality of quantum emissions is crucial for the effective performance of these networks. In this work we report a method for simultaneously implementing spectral purification and frequency shifting of single photons from QD sources to the c-band in a periodically poled lithium niobate waveguide. We consider difference frequency generation in the counter-propagating configuration to implement FC with the output emission bandwidth in units of GHz. Our approach establishes a clear path to integrating high-performance single-emitter sources in a hybrid quantum network.

A Novel Broadband Green Phosphor La2W2O9: Bi3+, and Its Application in High Color-Rendering Index pc-WLED

Broadband green phosphors have important applications in overcoming the blue-green (cyan) 470–510[Formula: see text]nm gap of phosphor-converted white LED (pc-WLED) and achieving high color rendering index (CRI) white lighting. In this work, a broadband green phosphor La2W2O9: [Formula: see text]Bi[Formula: see text] was synthesized by solid-state method. The phase, morphology and luminescence properties of the series of phosphors were systematically studied. The results showed the La2W2O9: [Formula: see text]Bi[Formula: see text] green phosphor exhibits a wide emission band in the range of 400–800[Formula: see text]nm with full width at half-maximum (FWHM) of 164[Formula: see text]nm, filling the cyan gap and reaching its peak at 550[Formula: see text]nm. The phosphor exhibits broadband excitation, and the excitation range covers the wavelength region of 200–500[Formula: see text]nm, and matches well with commercial ultraviolet LED. With the obtained broadband green phosphor, commercial CaAlSiN3:Eu[Formula: see text] red phosphor, commercial BaMgAl[Formula: see text]O17:Eu[Formula: see text] blue phosphor, and a 365[Formula: see text]nm commercial chip, a warm white pc-WLED device with a high color-rendering index (Ra[Formula: see text]97.4, R1–R15[Formula: see text]90) and low correlated color temperature (CCT[Formula: see text]3610[Formula: see text]K) was fabricated. The results demonstrate the wide range of applications for La2W2O9:Bi[Formula: see text] phosphor in the field of premium warm white LED lighting.

The Influence of Thickness and Spectral Properties of Green Color-Emitting Polymer Thin Films on Their Implementation in Wearable PLED Applications.

A systematic investigation of optical, electrochemical, photophysical, and electrooptical properties of printable green color-emitting polymer (poly(9,9-dioctylfluorene-alt-bithiophene)) (F8T2) and spiro-copolymer (SPG-01T) was conducted to explore their potentiality as an emissive layer for wearable polymer light-emitting diode (PLED) applications. We compared the two photoactive polymers in terms of their spectral characteristics and color purity, as these are the most critical factors for wearable lighting sources and optical sensors. Low-cost, solution-based methods and facile architecture were applied to produce rigid and flexible light-emitting devices with high luminance efficiencies. Emission bandwidths, color coordinates, operational characteristics, and luminance were also derived to evaluate the device's stability. The tuning of emission's spectral features by layer thickness variation was realized and was correlated with the interplay between H-aggregates and J-aggregates formations for both conjugated polymers. Finally, we applied the functional green light-emitting PLED devices based on the two studied materials for the detection of Rhodamine 6G. It was determined that the optical detection of the R6G photoluminescence is heavily influenced by the emission spectrum characteristics of the PLED and changes in the thickness of the active layer.

Luminescent color modulation of Zn/BaAl2O4:0.2%Eu phosphors for LED application

Spinel-type aluminate (ZnAl2O4) doped with europium (Eu) ions has garnered considerable attention in the field of luminescence. This study explores a series of Zn/BaAl2O4:0.2%Eu phosphors (x = 0∼0.25, x is for the mole fraction of BaAl2O4), fabricated through a high temperature solid-phase reaction method in air or reduction environment. In the case of phosphors synthesized in air, the photoluminescence emission (PL) spectra show a series of sharp emission peaks at 570 nm, 589 nm, 620 nm, 660 nm, and 710 nm, which are generated by the 5D0-7FJ (J = 0, 1, 2, 3, 4) level transitions in Eu3+. Time-resolved photoluminescence and X-ray photoelectron spectroscopy (XPS) characteristics also validate the presence of Eu3+ in samples synthesized in air. An intriguing observation is the abnormally strong emission peak at 570 nm under 346 nm excitation, originating from the Eu3+5D0-7F0 level transition. For x = 0.15, the corresponding CIE color coordinate is (0.3246, 0.3449), suggesting its potential application as a mono-doped and uni-matrix white phosphor. On the other hand, phosphors synthesized in reduction environment exhibit PL spectra with a wide emission band spanning from 400 nm to 550 nm, resulting from the electric-dipole-allowed transition of f-d state of Eu2+. The partial substitution of Zn2+ with Ba2+ significantly enhances the Eu2+ luminescence intensity. Moreover, an elevation of the mole fraction of Zn/BaAl2O4:0.2%Eu leads to a notable redshift (450 nm→500 nm) in the emission peaks of Eu2+ caused by lattice expansion, providing the adjustability of emitting color.

Dual-Template-Directed Zero-Dimensional Bismuth Chlorides: Structures, Luminescence, Photoinduced Chromism, and Enhanced Proton Conductivity.

Zero-dimensional (0D) hybrid organic-inorganic bismuth halides have attracted immense scientific interest as promising candidates for lead-free materials. Here, by using a typical solvothermal method, two mixed-cation-phase 0D hybrid bismuth chlorides of [HPDA][H2PDA]BiCl6 (1) and [Hbzim][H2PA]BiCl6 (2) (PDA = bis(4-pyridyl)amine, bzim = benzimidazole, PA = 2-picolylamine) have been assembled based on a series of organic amine guests. Both compounds exhibit interesting photoluminescence phenomena, in which compound 1 exhibits a double emission property of blue fluorescence and yellow-green phosphorescence simultaneously, while compound 2 exhibits wide-band yellow-green emission under visible light excitation. The luminescence mechanism is explained by experiments and theoretical calculations. In view of the fact that halometallate units and the conjugated nitrogen heterocyclic systems can act as electron donors and electron acceptors, respectively, both compounds exhibit free radical-driven photochromism induced by electron transfer under xenon lamp irradiation at room temperature. In addition, benefiting from abundant hydrogen bond networks in structures, the two compounds show significant temperature-dependent proton conduction behavior in the range of 298-343 K, and the proton conductivity of both compounds is significantly improved after light irradiation. Our study demonstrates two novel hybrid mixed-cation-phase 0D hybrid bismuth halides with photoluminescence, photochromism, and photomodulated proton conduction properties, which enriches the dual-template-directed metal halide system and provides a feasible scheme for the synthesis of photoresponsive smart materials.

Extended Surface Bands Enabled Lasing Emission and Wavelength Switch from Sulfur Quantum Dots.

The development of a lasing wavelength switch, particularly from a single inorganic gain material, is challenging but highly demanded for advanced photonics. Nonetheless, all current lasing emission of inorganic gain materials arises from band-edge states, and the inherent fixed bandgap limitation of the band-edge system leads to the inaccessibility of lasing wavelength switching from a single inorganic gain material. Here the realization of a single inorganic gain material-based lasing wavelength switch is reported by proposing an alternative lasing emission strategy, that is, lasing emission from surface gain. Previous efforts to achieve surface-gain-enabled lasing emission have been hindered by the limited gain volume provided by surface states due to the broad emission bandwidth and/or low emission efficiency. This challenge is overcome by introducing extended surface bands onto the surface of sulfur quantum dots. The extended surface bands contribute to a high photoluminescence quantum yield and narrow emission bandwidth, thereby providing sufficient gain volume and facilitating stimulated emission. When combined with whispering gallery mode microcavity, surface gain enabled lasing emission manifests an ultralow threshold of 8.3 µJcm-2. Remarkably, the reconfigurable perturbation to surface gain, facilitated by molecular affinity, allows for the realization of the lasing wavelength switch from a single inorganic gain material.

Bright Structural-Phase-Pure CsPbI3 Core-PbSO4 Shell Nanoplatelets With Ultra-Narrow Emission Bandwidth of 77 meV at 630 nm.

Achieving a narrow emission bandwidth islong pursued for display applications. Among all primary colors, obtaining pure red emission with high visual perception is the most challenging. In this work, CsPbI3 halide perovskite nanoplatelets (NPLs) with rigorously controlled 2D [PbI6]4- octahedron layer number (n) are demonstrated. A perovskite core-PbSO4 shell structure is designed to prevent aggregation and fusion between NPLs, enabling consistent thickness and quantum confinement strength for each NPL. Consequently, exact n = 4 CsPbI3NPLs are demonstrated, exhibiting emission peaks around 630nm, with very narrow spectral bandwidths of <24nm and high absolute photoluminescence quantum yields up to 85%. The emission of n = 4 NPLs falls exactly within the pure-red region, closely aligning with the International Telecommunication Union Recommendation BT.2020 standard. Measurements suggest predominant stability and color homogeneity compared to traditional red-emitting CsPbIxBr3- x nanocrystals. Finally, proof-of-concept pure-red emissive light-emitting diodes (LEDs) are demonstrated by integrating n = 4 CsPbI3 NPLs films with a blue LED chip, showing an excellent external quantum efficiency of 18.3% and high brightness exceeding 3 × 106 nits. Stringent requirements for future display technologies, are satisfied based on the high color purity, stability, and brightness of CsPbI3 NPLs.

Multimode optical thermometry using CaWO4 emission band

Optical thermometry has emerged as a promising technique for remote temperature sensing in plenty of applications, where traditional contact methods are useless. To date, many sensing strategies have been developed and realized, but most of them are based on monitoring of the single temperature dependent parameter. Here, we report simple dual-center materials (Eu3+ and Sm3+-doped CaWO4) that provide multimode optical thermometry. In addition to standard ratiometric approach based on intensity ratio between host and lanthanide emission bands, spectral position and bandwidth of CaWO4 emission band were successfully utilized as temperature sensitive parameters for the first time. It was shown that multimode sensing leads to broadening of temperature working range and enhances reliability of thermal sensing. The best thermometric characteristics were achieved for CaWO4:Sm3+ sample: Sr = 1.29 % K−1@273–673 K and δT = 0.15 K.