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    Mach-Zehnder-based measurement of light emitting diodes temporal coherence

    Lobera J.Lopez A.M.Palero V.Andres N....
    5页
    查看更多>>摘要：? 2022 The AuthorsObjectives: The main objective of this work is to validate a Mach-Zehnder based interferometric method to measure the temporal coherence length of broadband finite size light sources such as Light Emitting Diodes (LEDs), and give a qualitative value of the temporal coherence length of white LEDs, for which nor their spectral width neither their emission peak wavelength are clearly defined. Motivation: Low-coherence light sources such as LEDs have opened many possibilities in applications in which using lasers introduces coherent noise (speckle) that hinders the performance of interferometric measurement techniques. The coherence length is an important characteristic of light sources for scientific applications related to diffraction, holography, tomography, or interferometry. The spatial coherence of a source depends on the distance from the source to the observation plane and its size, while the temporal coherence is related to the emission spectral width and the emission peak wavelength. Therefore, the temporal coherence is a characteristic of each source. Methodology and results: In this work, we use a Mach-Zehnder interferometer for the first time to measure the coherence degree and the temporal coherence length of quasi-monochromatic LEDs. We validate the technique by comparing the results to those obtained directly from the spectrum. Then, we use the tested interferometric method to measure the temporal coherence length of a white LED, for which neither the width of the spectrum nor the emission peak wavelength, are clearly defined. In this case, the Wiener-Khinchin theorem is used to validate the interferometric technique. A very interesting property of the method is that the temporal coherence length is obtained from a single measurement, without needing to perform a scanning. This method can be used also for other non-coherent sources such as halogen lamps, pulsed lasers, and so on. The obtained results will improve the characterization of light sources and the applications dealing with physical optics and electromagnetic interference.
      原文链接:
    • NSTL
    • Elsevier

    Ligand-mediated evolution from CsPbBr3 to Cs4PbBr6/CsPbBr3 perovskite composites with intense green emission

    Liang W.Li T.Zhu C.Guo L....
    5页
    查看更多>>摘要：? 2022 Elsevier GmbHHerein, CsPbBr3 and Cs4PbBr6/CsPbBr3 perovskite composites have been synthesized by a simple supersaturated recrystallization procedure. X-ray diffraction and absorption spectra confirm the evolution from CsPbBr3 to Cs4PbBr6 by adding oleic acid and oleylamine simultaneously, which leads to the formation of green emissive Cs4PbBr6/CsPbBr3 perovskite composites. Gaussian fitting of the emission spectra and luminescent lifetime investigation indicate that the green emission is attributed to both Cs4PbBr6 and CsPbBr3, which originates from the exciton radiative recombination mediated by the trap states and the electron-hole recombination, respectively. Moreover, the emissive Cs4PbBr6 can further promote the emission of CsPbBr3 by energy transfer process in Cs4PbBr6/CsPbBr3 composites. The photoluminescence intensity declines by less than 10 % after 60 days of storage in ambient environment, reflecting the excellent stability of the composites for lighting and displaying application.
      原文链接:
    • NSTL
    • Elsevier

    Spectroscopic characteristics of barium sulfoborophosphate glasses doped samarium ions: Evaluation of Judd-Ofelt intensity parameters and radiative properties

    Musa Y.Muhammad T.Isma'ila A.Abubakar A.U....
    5页
    查看更多>>摘要：? 2022 Elsevier GmbHHerein, barium sulfoborophoshate (PBBs) glasses activated with varying contents of Sm3+ ions have been prepared by melt quench technique and optically characterized by means of ultraviolet visible, photoluminescence and fluorescence spectrophotometers to ascertain their spectroscopic traits. UV–Vis-NIR spectra revealed the occurrence of several absorption bands corresponding to the transitions from the ground state to various excited states of the Sm3+ ion. Meanwhile the photoluminescence spectra displayed four prominent emission bands centered at 559, 596, 642 and 709 nm. The as-prepared glass sample with 0.7 mol. % of samarium ions concentration disclosed highest luminescence intensity and quenched afterward. Besides, Judd–Ofelt approach has been applied for the f-f transition of Sm3+ ions to calculate intensity parameters (Ωλ (λ = 2, 4, 6). Conclusively, the exceptional values achieved for branching ratio >50%, color purity (99.56 %) and the quantum efficiency (86.21 %) declare the feasibility of the present glass host specifically PBBsSm0.7 sample for visible red laser and display device applications.
      原文链接:
    • NSTL
    • Elsevier

    Zr-doped silver niobates for photocatalytic degradation of methylene blue and Rhodamine B dyes

    Khan M.Y.Khan A.Khor C.M.Khan M.M....
    5页
    查看更多>>摘要：? 2022 Elsevier GmbHPristine silver niobate and Zr-doped silver niobates as photocatalysts were synthesized by the sol-gel method. The synthesized samples were characterized by X-ray diffraction (XRD) and were found to contain both AgNbO3 and AgNb3O8. Fourier transform infrared (FT-IR) shows that the Nb-O bonds among the samples are different and may be attributed to the two types of silver niobates. Field emission scanning electron microscopy (FESEM) showed changes in morphologies of particles with increasing Zr-doping with average particle size ranging from 0.89 μm to 1.21 μm. The Tauc plots indicate that Zr-doped silver niobates have lower band-gap energies than their undoped counterpart. Furthermore, Zr-doped silver niobates also have a lower rate of electron-hole recombination than the undoped silver niobate as proven by the PL analysis. The photocatalytic degradation studies showed that Zr doping improved the performance of silver niobate for both Rhodamine B and methylene blue dyes. Through the present study, the link between Zr-doping and its role in dye degradation by silver niobates could be established.
      原文链接:
    • NSTL
    • Elsevier

    Enhanced visualization of tissue microstructures using swept-source optical coherence tomography and edible oil as optical clearing agent

    Banerjee A.Poddar R.
    5页
    查看更多>>摘要：? 2022 Elsevier GmbHOptical clearing agents are chemicals which helps in tissue optical clearing by making skin more optically transparent to light. These chemical agents reduce scattering caused by tissue and improves light penetration. Optical coherence tomography (OCT) has been used as a non-invasive imaging tool for decades. It can achieve resolutions up to less than 10 μm, which is a major highlight of this technique. This feature makes it suitable for visualizing microstructures and layers present in skin. Dermal imaging brings forth various challenges that needs to be overcome in order achieve better imaging results. The light is attenuated due to scattering caused by different tissue structures and layers present in the skin. This paper aims to improve the OCT imaging signal and enhance its contrast using optical clearing agents. The aim is also to visualize the microstructures present in the skin and quantitatively estimate the sizes of different structures and layers present in the skin.
      原文链接:
    • NSTL
    • Elsevier

    Double negative circular shaped inductively coupled metamaterial power splitter for the C-, X band applications

    Siddiky A.M.Faruque M.R.I.Abdullah S.Islam M.T....
    5页
    查看更多>>摘要：? 2022 Elsevier GmbHExternal electric and magnetic field assisted circular split ring resonator (CSRR) with inductively coupled is introduced in this paper. This subwavelength based design is placed on the dielectric medium that exhibits three resonant frequencies at 6.3 GHz with the bandwidth 5.1–6.9 GHz, at 8.7 GHz with the bandwidth 8.3–9.0 GHz and at 11.3 GHz with the bandwidth 10.8–11.6 GHz. This design topology with inductive coupling helps to confine the electromagnetic interaction in a specific region to enhance the surface current on the design where the current is split into two areas. Negative permeability region is situated from (6.0–7.0, 8.6–9.0, 11.2–11.6) GHz, negative permittivity from (6.2–7.1, 8.7–9.0, 11.3–11.7) GHz, and negative refractive index from (6.2–7.5, 8.7–9.4, 11.3–12.1) GHz. The electric and magnetic field distribution with surface current distribution is observed for different resonant frequencies within the functional frequency range from 1 to 18 GHz. Different rotational configurations with the width variation and different substrate material for analyzing effective parameters are carried out for the parametric study.
      原文链接:
    • NSTL
    • Elsevier

    Optical soliton perturbation with Fokas–Lenells equation via enhanced modified extended tanh-expansion approach

    Bayram M.Esen H.Ozisik M.Secer A....
    5页
    查看更多>>摘要：? 2022 Elsevier GmbHPurpose: In this article, we establish novel solutions for the perturbed nonlinear Lenells equation, which is one of the model to investigate soliton dynamics through a polarization-preserving optical fiber, by using an enhanced modified extended tanh expansion method. Our aim is, not only gain various analytical optical soliton solutions of the investigated equation but also demonstrate the role of the investigated model's parameter on soliton behavior, by selecting the different soliton shapes, which are bright and singular. Methodology: In order to apply the proposed method, we first obtained the nonlinear ordinary differential form of the investigated equation with the help of complex wave transform. Then, by applying the method, we obtained the polynomial form and, accordingly, a system of linear equations. The solution of the linear system of equations gave different solution sets containing the values of the investigated model and the proposed method. After choosing the appropriate set from these sets and applying the solution functions and wave transformation provided by the method, we obtained the optical soliton solutions by providing the main equation. In order to support and better explain the obtained results, various graphic presentations were made by assigning some special values to the parameter values and explained in detail in the relevant sections. Findings: By applying the proposed method effectively, many analytical optical solutions of the model have been obtained and different soliton solutions have been obtained. Such as, bright, smooth V-shape, dark–bright in different amplitude, periodic singular, bright compacton like, composite dark–bright, periodic bright, breather like. More importantly, two different soliton types such as bright and singular were examined for the effect of model parameters on soliton behavior. The analysis shows that the model parameters have a significant effect on the soliton behavior and this effect might be different depending on the soliton types. Originality: Although the proposed method was applied to the investigated problem for the first time and different soliton types were obtained, the study differs from other studies in terms of examining the effect of model parameters on soliton behavior.
      原文链接:
    • NSTL
    • Elsevier

    Photonic crystal fiber modulator based on surface plasmon resonance

    Zheng J.Wang J.Ning T.Qu J....
    5页
    查看更多>>摘要：? 2022In this paper, a photonic crystal fiber (PCF) modulator based on surface plasmon resonance (SPR) is proposed. Two optical functional materials, liquid crystal and magnetic fluid, were filled in the air holes with aurum film of PCF to excite SPR. After applying electric and magnetic fields, the effective refractive index of the SPP (surface plasmon polaritons) mode in PCF would be changed by liquid crystals and magnetic fluids, which affected the resonance wavelength and loss peak. The modulation feasibility of the structure was verified by the full vector finite element method. The results show that the proposed modulator can independently realize electro-optical and magneto-optical modulation with a characteristic of wavelength tunability. At the wavelength of 1450 nm, the electro-optic modulation voltage reaches 2.5 V, and the extinction ratio reaches a maximum of 46.11 dB/mm. Only 0.43 mm length is required to meet communication requirements. At the same time, the magnetic field sensitivity and extinction ratio of the modulator reach 17.82 pm/Oe and 25.18 dB/mm, respectively, at the wavelength of 1682 nm. The modulator has the characteristics of high extinction ratio, low modulator voltage and miniaturization, which can be used in optical fiber transmission systems that need to be integrated.
      原文链接:
    • NSTL
    • Elsevier

    Synthesis and characterization of the optical MgO-BaO-B2O3-TeO2-MnO2 glass system

    SamdaniAlharshan G.A.Haritha L.Sekhar K.C....
    5页
    查看更多>>摘要：? 2022 Elsevier GmbHThe paper reports on the preparation and characterization of the optical 15MgO-15BaO-(59.5-x)B2O3-(10+x)TeO2 glass system, with (x = 0 (MBBMn-1), 10 (MBBMn-2), 20 (MBBMn-3), and 30 mol% (MBBMn-4)). Using the melt-quench experimental synthesis method, we prepared our glass system and the influence of TeO2 on the physical, structural, optical, and radiation shielding properties were studied. The bandgap (Eopt), Urbach energy (?E), refractive index (n), and other parameters were calculated using UV data. The stopping power and range of electron, proton, α-particle and carbon ion were estimated for kinetic energies 0.015–15 MeV. Also, the fat and thermal neutron cross sections were estimated following the standard procedures. The structural evaluation of the glass network as well as the functional groups inherent in the structure was explored using FTIR and Raman spectra. At particle energy of 15 MeV, the range of electron was estimated as 25.89, 22.47, 20.49, and 19.79 mm in MBBMn-1–MBBMn-4 respectively. Also, for proton, α-particle, and carbon ion the projected range was 1080, 100.02 and 10.67 μm in MBBMN-1; 1030, 96.86, and 10.44 μm in MBBMN-2; 986, 93.95, 10.26 μm in MBBMN-3; and 942, 91.03, and 10 μm in MBBMN-4. The fast neutron removal cross section was 0.1069, 0.1066, 0.1063, and 0.1044 cm-1 for MBBMn-1 – MBBMn-4 in that order while the total cross section of thermal neutrons declined from 95.7025 to 74.8538 as the molar concentration of TeO2 increased from 10 to 40 mol% in the MBBMn glasses.
      原文链接:
    • NSTL
    • Elsevier

    Exploring the solitons for multiple-core couplers having optical metamaterials using the modified extended direct algebraic method

    Eldidamony H.A.Ahmed H.M.Arnous A.H.Ali Y.S....
    5页
    查看更多>>摘要：? 2022 Elsevier GmbHThis paper investigates the optical solitons for the cubic–quartic (CQ) multiple-core couplers with optical metamaterials having Kudryashov's sextic power law of arbitrary refractive index. With the aid of the modified extended direct algebraic method, various types of solutions are raised. The obtained solutions include bright soliton solutions, dark soliton solutions, singular soliton solutions, singular periodic solutions, hyperbolic-type solutions, rational-type solutions, and exponential-type solutions. Moreover, for the physical illustration of the obtained solutions 2D, 3D, and contour graphs are presented.
      原文链接:
    • NSTL
    • Elsevier