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The optical and luminescence properties of Zn1-xGdxO (0≤x≤0.07) quantum dots synthesized via tetraethyl orthosilicate assisted colloidal regime for laser diodes application potential
摘要： Here, we report about Zn1-xGdxO (0≤x≤0.09) semiconductor quantum dots synthesized via tetraethyl orthosilicate assisted colloidal regime for first time. The X-ray diffraction disclosed that the introduction of Gd ions in Zn sites of ZnO did not affect its hexagonal phase. The transmission electron microscopy divulged that the Gd ions caused an increasing of the particle size of Zn1-xGdxO QDs from 3 nm to 18 nm. The EDAX spectra inspected the stoichiometry and high purity of the synthesized Zn1-xGdxO QDs. The doping of ZnO QDs by Gd ions gives rise to a red shifting of the absorption and emission optical spectra. The doping of ZnO QDs by Gd ions instigates a reduction of the ZnO band gap from 3.3 to 2.8 eV. The doping of ZnO QDs by Gd ions improves the luminescence intensity, reduces the spectral width and suppresses the crystal defects. The quantum yield improved from 31% to 94%. These outstanding behaviors give rise to develop prohibitive superiority laser diode from the nanocrystalline Zn1-xGdxO semiconductor quantum dot.
关键词： Quantum yield,Optical absorption,Luminescence,Crystal structures,Quantum dot
更新于2025-09-16 10:30:52
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Improving Output Power of InGaN Laser Diode Using Asymmetric In0.15Ga0.85N/In0.02Ga0.98N Multiple Quantum Wells
摘要： Herein, the optical ?eld distribution and electrical property improvements of the InGaN laser diode with an emission wavelength around 416 nm are theoretically investigated by adjusting the relative thickness of the ?rst or last barrier layer in the three In0.15Ga0.85N/In0.02Ga0.98N quantum wells, which is achieved with the simulation program Crosslight. It was found that the thickness of the ?rst or last InGaN barrier has strong e?ects on the threshold currents and output powers of the laser diodes. The optimal thickness of the ?rst quantum barrier layer (FQB) and last quantum barrier layer (LQB) were found to be 225 nm and 300 nm, respectively. The thickness of LQB layer predominantly a?ects the output power compared to that of the FQB layer, and the highest output power achieved 3.87 times that of the reference structure (symmetric quantum well), which is attributed to reduced optical absorption loss as well as the reduced vertical electron leakage current leaking from the quantum wells to the p-type region. Our result proves that an appropriate LQB layer thickness is advantageous for achieving low threshold current and high output power lasers.
关键词： asymmetric multiple quantum wells,optical absorption loss,InGaN laser diodes,barrier thickness,electron leakage current
更新于2025-09-16 10:30:52
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Optical absorption and dispersion properties of 2-aminoanthracene-9,10- dione thin films for photodetector applications
摘要： Recent evidence suggests that the need for employing a new characteristic with low-cost preparation tools and high performance for applications. These properties have been achieved by using a high stable 2-aminoanthracene-9,10- dione thin films (AAD), prepared by thermal evaporation technique under a vacuum of 10?5 Torr. The surface of the films was checked by SEM for studying the RMS-roughness characteristics and grain – boundary influence. Added to this study, the crystalline performance was also considered as the main requirement for identifying the main crystal parameters. Most important results were focused on TGA results for confirming the thermal stability through the chosen measurements. The investigation of the spectral dependence of the absorption of the AAD films specifies the occurrence of high probability for indirect transition as compared to the direct allowed with energy gaps of 1.55 and 2.28 eV. The dispersion energy and oscillator energy, as well as most parameters, were computed using the well-known Wimple–DiDomenico formula under consideration of the single oscillator model. The spectral dependence of the linear and nonlinear controlling parameters were studied for subscription the prospect applications in photodetectors.
关键词： Thermal evaporation,Phototransient properties,Optical absorption,Thermal stability
更新于2025-09-16 10:30:52
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Theoretical Study of GaN/BP van der Waals Nanocomposites with Strain-Enhanced Electronic and Optical Properties for Optoelectronic Applications
摘要： Construction of van der Waals (vdW) nanocomposites can advance two-dimensional (2D) materials with desired properties and significantly widen their applications. Based on first-principles calculations, we verify that a gallium nitride/boron phosphide (GaN/BP) vdW nanocomposite is a direct-gap semiconductor with type-I band alignment. The nanocomposite shows significant optical properties in the visible and near-ultraviolet regions. Additionally, the bandgap, band edge positions, and optical absorption of the GaN/BP nanocomposite can be tuned by in-plane biaxial strains. A biaxial tensile strain with a strength of 3% can induce the type-II band alignment in the GaN/BP nanocomposite, which results in effective separation of the photo-generated charge carriers. Meanwhile, the application of biaxial strain can also significantly enhance the optical absorption of the GaN/BP nanocomposite in the near-infrared and visible regions. Furthermore, we show that the adjustment of interlayer coupling is also an effective way to modulate the electronic and optical properties of the GaN/BP nanocomposite. Our studies reveal the potential application of the GaN/BP nanocomposite in optoelectronic devices.
关键词： first-principles calculations,optical absorption,strain engineering,band structure,GaN/BP nanocomposite
更新于2025-09-16 10:30:52
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Identifying Clusters and/or Small-Size Quantum Dots in Colloidal CdSe Ensembles with Optical Spectroscopy
摘要： It is well-known that optical absorption and photoluminescence (PL) provide information that is sensitive to the size and size distribution of colloidal binary semiconductor quantum dots (QDs). To explore the nature of reaction products, clusters, and/or small-size QDs, we show that it is important to perform as well photoluminescence excitation (PLE) spectroscopy. For two non-hot-injection reactions of cadmium oleate (Cd(OA)2) and selenium (Se) in 1-octadecene (ODE), we show that sequentially extracted products displayed a similar apparent red shift in both absorption and PL with a full width at half-maximum (fwhm) of ～30 nm. We demonstrate that one reaction (with the presence of diphenyl phosphine (HPPh2)) produced multiple types of clusters (with slightly different optical properties) in one ensemble, while the other reaction (without HPPh2) yielded primarily small-size QDs. Our findings provide evidence for the probable existence of clusters within small-size CdSe QD products, the existence of which complicates the size determination of small-size CdSe QDs.
关键词： optical absorption,photoluminescence,photoluminescence excitation spectroscopy,clusters,CdSe quantum dots
更新于2025-09-16 10:30:52
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Analysis of Si3N4 waveguides for on-chip gas sensing by optical absorption within the mid-infrared region between 2.7 and 3.4???μm
摘要： We theoretically investigated the use of a Si3N4 on SiO2 waveguide as an optical interaction part with sensed molecules for multi-gas wideband on-chip spectroscopic sensing. From the analysis, we show that a simple strip Si3N4 waveguide can be employed to achieve acceptable values of performance in term of detection limit, compactness, polarization, and fabrication tolerance for the detection of water vapor (H2O), carbon dioxide (CO2), Nitrous oxide (N2O), Ammonia (NH3), Ethylene (C2H4), and Methane (CH4) gas molecules, with a wideband operation between 2.7 and 3.4 μm optical wavelength. The results show that a simple Si3N4 waveguide structure could attain competitive performance required for generic on-chip spectroscopic sensing for environmental and agricultural usage.
关键词： gas sensing,optical absorption,mid-infrared,on-chip spectroscopic sensing,Si3N4 waveguide
更新于2025-09-16 10:30:52
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Wideband saturable absorption in Metal-organic frameworks (MOFs) for mode-locking Er- and Tm-doped fiber laser
摘要： We fabricate a Metal-organic frameworks (MOFs) Saturable absorber (SA) based on a microfiber. Nonlinear optical absorption of the MOF SA is characterized systmatically. The modulation depth is measured to be 6.57 % and 14.25 % at 1.5 and 2 μm spectral ranges, respectively. We report ultrashort pulse generation in both Er- and Tm-doped fiber lasers by using a same microfiber-based MOF SA, operating 384 fs and 1.3 ps pulse duration at 1563 nm and 1882 nm, respectively. To the best of our knowledge, this is the first report on a MOF based fiber laser at near infrared spectral ranges. Our findings validate the applicability of MOF as a broadband SA for ultrafast photonic applications.
关键词： Ultrafast photonics,Saturable absorber,Metal-organic frameworks,Fiber laser,Nonlinear optical absorption
更新于2025-09-16 10:30:52
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Cu2FeSnS4 Nanoparticles: Potential Photovoltaic Absorption Materials for Solar Cell Application
摘要： Quaternary semiconductor Cu2FeSnS4 (CFTS) nanoparticle powder have been prepared by thermal analysis and electrochemical characterization. Powder XRD and Raman spectroscopy confirm the phase and structure of the prepared nanoparticles. The optical absorption studies reveal that the CFTS nanoparticles have a direct optimal band gap in the range from 1.32 to 1.5eV, which indicates that these nanoparticles are potential absorber materials for thin-film photovoltaic application. The synthesized CFTS nanoparticles were transformed to the ink form and the obtained nanoparticle ink coated on a FTO conducting substrate (surface resistivity-13Ω/sq). The catalytic activity of the substrate was analyzed by electrochemical impedance spectroscopy (EIS) and cyclic voltammogram (CV) curves. The appropriate optical band gap and stable electrical properties indicate that Cu2FeSnS4 Nanoparticles are potential materials for thin-film photovoltaic application.
关键词： optical absorption studies,Cu2FeSnS4 (CFTS),electrochemical impedance spectroscopy analysis,facile chemical route method,Raman spectroscopy
更新于2025-09-16 10:30:52
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Thermoreflectance-based measurement of facet optical absorption in high power diode lasers
摘要： Severe heating due to partial absorption of outcoupled emission at the facet of a high-power diode laser can lead to catastrophic optical damage. The degree of absorption and subsequent heating at the facet is a function of the emission wavelength, the absorption properties of facet coatings and passivation layers, and the age of the device. The ability to quantify facet absorption is an essential step toward improving the reliability and maximum output power of diode laser systems. In this work, we have developed a technique to measure facet absorption in diode lasers using a combination of facet thermoreflectance imaging and a heat transport model. The approach can be used for a wide range of both coated and uncoated diode lasers.
关键词： catastrophic optical damage,diode lasers,optical absorption,thermoreflectance
更新于2025-09-12 10:27:22
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Absorption spectra, ligand field parameters and g factors of Cr<sup>3+</sup> doped α-Al<sub>2</sub>O3 laser crystal: <i>ab initio </i>calculations
摘要： In this paper we present, in the unified frame, the results of the ab initio investigations of absorption spectra, ligand field parameters and g factors for three valence chromium doped α-Al2O3 crystal. Our calculations are based on a new methodology applied to a cluster [CrO6]9- embedded in an extended point charge field of host matrix ligands. After the differential functional theory (DFT) optimization of the doped crystal, a vibrational theoretical spectroscopic study based on infrared (IR) spectroscopy has been employed in order to confirm the stability of the optimized doped crystal structure. The ab initio energy calculation of the electronic states and corresponding wave functions of Cr3+ are documented from the complete active space self-consistent field (CASSCF). The improved energy states from the N-electron valence second order perturbation theory (NEVPT2), second order dynamic correlation dressed complete active space (DCD-CAS2), difference dedicate configuration interaction with three degrees of freedom (MRDDCI3) and spectroscopy-oriented configuration interactions (SORCI), were analyzed. Based on the ab initio ligand field theory (AILFT) procedure we extracted ligand field (LF) parameters and spin-orbit coupling constant which were used to recalculate the energy levels of the studied system. In addition, g factors for the ground state 4A2 of Cr3+ ion in corundum are calculated taking into account the full configuration interaction. The results obtained are discussed and comparisons with measured values from the literature show a reasonable agreement, which justifies and recommend this new route of investigation.
关键词： Ligand field,g factors,Optical absorption spectra,Al2O3:Cr3+,Ab initio calculations
更新于2025-09-12 10:27:22