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A monolithic on-chip magneto-optical isolator with 3 dB insertion loss and 40 dB isolation ratio
摘要： On-chip optical isolators constitute an essential building block for photonic integrated circuits (PICs). Here we experimentally demonstrated a magneto-optical isolator monolithically integrated on silicon featuring 3 dB insertion loss and 40 dB isolation ratio, both of which represent significant improvements over state-of-the-art. The isolator is also fully passive and operates under a simple unidirectional magnetization scheme. Such superior performance is enabled through a three-way combination of a strip-loaded waveguide design, a compositionally optimized chalcogenide glass as the light guiding medium, and low-loss taper structures created via gray-scale lithographic processing. The device represents an important step towards a practical solution for on-chip isolation in PICs.
关键词： Integrated optics devices,Magneto-optical materials,Chalcogenide glass,Resonators,Grayscale-lithography,Isolators
更新于2025-09-23 15:21:21
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Giant exchange bias in the single-layered Ruddlesden-Popper perovskite
摘要： Exchange bias (EB) as large as ～5.5 kOe is observed in SrLaCo0.5Mn0.5O4, which is the highest ever found in any layered transition-metal oxides including Ruddlesden-Popper series. Neutron-diffraction measurement rules out long-range magnetic ordering and together with dc magnetic measurements suggests formation of short-range magnetic domains. Ac magnetic susceptibility, magnetic memory effect, and magnetic training effect con?rm the system to be a cluster spin glass. By carrying out density functional calculations on several model con?gurations, we propose that EB is originated at the boundary between Mn-rich antiferromagnetic and Co-rich ferromagnetic domains at the subnanoscale. Reversal of magnetization axis on the Co side alters the magnetic coupling between the interfacial Mn and Co spins, which leads to EB. Our analysis infers that the presence of competing magnetic interactions is suf?cient to induce exchange bias and thereby a wide range of materials exhibiting giant EB can be engineered for designing novel magnetic memory devices.
关键词： Ruddlesden-Popper perovskite,Exchange bias,cluster spin glass,magnetic memory devices
更新于2025-09-23 15:21:21
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Structural transformations and spectroscopic properties of Ni-doped magnesium aluminosilicate glass-ceramics nucleated by a mixture of TiO2 and ZrO2 for broadband near-IR light emission
摘要： Ni:MgAl2O4 spinel shows a reversible random Ni2t site redistribution with increasing temperature. With the aim of determining the influence of the structure evolution induced by heat-treatment on the nature of luminescence centers in NiO-doped spinel-based magnesium aluminosilicate glass-ceramics nucleated by a mixture of TiO2 and ZrO2, the detailed spectroscopic study of the initial glass during its heat-treatments at increasing and decreasing temperatures has been performed and accompanied by an XRD analysis and Raman spectroscopy. The initial glass was X-ray amorphous. Its optical spectrum is mainly formed by absorption of [5]Ni2t sites with a small amount of [4]Ni2t ones. Crystals of the nucleating catalyst, ZrTiO4, about 4 nm in size, appear during heat-treatment at 800 °C, while the absorption spectrum of Ni2t ions remains near unchanged. At 850 °C, spinel crystals with size of about 6 nm precipitate, which is accompanied by a broadband luminescence in the near-IR centered at 1330 nm with a bandwidth of 380 nm. At 950 °C, there is a slight reduction in intensity of absorption bands attributed to [6]Ni2t site redistribution with increasing temperature. A decrease in the amount of the [6]Ni2t luminescent centers is not accompanied by a decrease in the luminescence intensity because of the increased size of spinel crystals. Additional low-temperature heat-treatment does not lead to a redistribution between [6]Ni2t sites in spinel crystals in favor of [6]Ni2t ones. An increase of the luminescence intensity after low-temperature heat-treatment is associated with additional spinel crystallization.
关键词： Glass-ceramics,Luminescence,Spinel,Heat-treatment,Nickel,Absorption
更新于2025-09-23 15:21:21
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nanoparticles
摘要： We report changes on the magnetic behavior of the Heavy-Fermion ferromagnetic YbNi2 alloy when reducing the size of the particles to the nanometer scale by high-energy ball milling. The milling process induces a reduction on the particle size of the bulk alloy down to 10 (2) nm and a lattice strain of 1.8 (2)%, for 30 h of milling time, as calculated from the x-ray diffraction data. The ferromagnetic transition at TC =10.5 K in the bulk alloy tends to disappear whereas other magnetic transitions arise at lower temperatures with the milling process. The AC magnetic susceptibility of the 30 h milled sample shows a frequency independent peak at 3 K, in a wide range of frequencies, consistent neither with superparamagnetic nor simple freezing of the magnetic moments, and as expected for a ferromagnetic behavior. However, from the specific heat measurements in the 30 h milled sample, a peak at 3.6 K is shifted respect to that observed in the AC magnetic susceptibility, as found in spin glasses. Additionally, the specific heat on nanometric samples show reduced magnetic contributions respect to the bulk alloy with ?cmax around 0.45 J/molK. The results are explained by the influence of magnetic inhomogeneities and disorder of the alloys enhanced by the milling process in the ensemble of nanoparticles.
关键词： Specific heat,Ferromagnetic,Spin glass,Magnetic properties,Yb alloys
更新于2025-09-23 15:21:21
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Structural determination of phosphosilicate glass based on first-principles molecular dynamics calculation
摘要： We report static and dynamic first-principles calculations determining the structure and electronic properties of phosphosilicate glass (PSG). A stable structure of PSG with composition of (SiO2)x(P2O5)y was calculated by simulated annealing based on Car–Parrinello molecular dynamics (CPMD) with a real-space density functional theory (RSDFT) code. As a result, phosphorus (P) atoms in PSG were four-fold coordinated with oxygen (O) atoms and one of the four PO bonds was dangling toward the interstitial region (an –O3PO configuration). We also compared the structures having a different number of O atoms to discuss the stable configuration of PSG in the realistic situation of phosphoryl chloride (POCl3) annealing. We found that –O3PO is most stable for O2-rich conditions, whereas three-coordinate P (an –O3P configuration) becomes stable in O2-poor conditions. The candidates of the states which create levels inside the bandgap of PSG were also calculated.
关键词： phosphosilicate glass,molecular dynamics,first-principles calculation,electronic properties,POCl3 annealing
更新于2025-09-23 15:21:21
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Structural and optical properties of Gd+3 doped Bi2O3-GeO2 glasses and glass-ceramics
摘要： The gadolinium doped Bi2O3-GeO2 glasses and glass-ceramics have been synthesized by melt quenching and heat treatment. Structural and optical properties of prepared glasses and glass-ceramics have been examined by X-ray diffraction (XRD), Fourier transform infrared, absorption and emission measurements. XRD results have shown that the precipitated crystalline phases in glass-ceramics samples are Bi2GeO5, Bi2Ge3O9 and Bi4Ge3O12. [BiO3] and [GeO4] units are the main structural units present in Bi2O3-GeO2 glass and glass-ceramic network confirmed by IR spectra. Optical band gap values of prepared glass and glass-ceramic systems obtained from absorption spectra vary from 2.01 to 3.34 eV. The optical band gap values of glasses are larger than glass-ceramics. Bi2O3-GeO2 glass-ceramics have higher density values than glasses and densities present an increase with the elevated Gd3+ content. It is suggested that the luminescence under 366 nm excitation has been ascribed to different Bi-related emission centers. The CIE color coordinates and CCT values obtained under 366 nm excitation confirm that the Gd3+ doped bismuth germanate glasses and glass-ceramics exhibit white light emission. The most promising material for white light emitting applications within our research is found to be GC-2Gd with coordinates of (0.327, 0.314) and a CCT of 5753 K.
关键词： glass,bismuth,glass-ceramic,Gadolinium,white light,Bi2O3-GeO2
更新于2025-09-23 15:21:01
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Color conversion properties of various thick-film phosphor-in-glasses depending on structural design for white LEDs
摘要： Thick-film phosphor-in-glasses (PiGs) were fabricated via a screen-printing method with various phosphor layer structures, to compose a white LED. Green (Lu3Al5O12:Ce3+) and red (CaAlSiN3:Eu2+) phosphors were mixed, layered and patterned on a glass substrate. The chromaticity of each structured PiG was tuned to achieve a white LED by varying phosphor content and thickness. The emission spectra and the related various color conversion properties, including color coordinates, correlated color temperature (CCT), color rendering index (CRI), luminous efficacy (LE) and the color gamut of the mounted PiGs with different phosphor layer structures were examined and compared. Time-resolved photoluminescence (TRPL) measurements of the white LEDs with various phosphor layer structural designs were also obtained and compared. It was observed that spectral variation depended on the PiG layer structure. A proper PiG layer structural design was discussed for practical applications.
关键词： glass,thick films,LED,Phosphors
更新于2025-09-23 15:21:01
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~2????m emission properties and energy transfer processes in Tm3+ doped Bi2O3-GeO2-Na2O glass laser material
摘要： Tm3+ doped Bi2O3-GeO2-Na2O glass samples were synthesized by conventional melt-quenching method. The Raman spectra measurements showed the maximum phonon energy of prepared glass is 794 cm-1, which is considerably lower than silicate glasses. Based on the measured absorption spectra, Judd-Ofelt intensity parameters, spontaneous radiative transition probabilities and radiative lifetimes were calculated to elucidate the radiative properties of Tm3+ in the presented glass. Intense near infrared emission around ~2 μm was obtained under the pump of 808nm laser diode. A large stimulated emission cross section (5.51×10-21 cm2 at 1851 nm) of Tm3+: 3F4 → 3H6 was achieved in the prepared bismuth germanate glass doped with 1 mol% Tm2O3. Besides, the energy transfer processes among Tm3+ were analyzed using the extended overlap integral method. These results indicate that the presented glass is a promising candidate for ~2 μm laser applications.
关键词： Energy transfer,Thulium,Bismuth germanate glass,Emission properties
更新于2025-09-23 15:21:01
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Self-focusing of UV radiation in 1 mm scale plasma in a deep ablative crater produced by 100 ns, 1 GW KrF laser pulse in the context of ICF
摘要： Experiments at the GARPUN KrF laser facility and 2D simulations using the NUTCY code were performed to study the irradiation of metal and polymethyl methacrylate (PMMA) targets by 100 ns UV pulses at intensities up to 5 3 1012 W cm?2. In both targets, a deep crater of length 1 mm was produced owing to the 2D geometry of the supersonic propagation of the ablation front in condensed matter that was pushed sideways by a conical shock wave. Small-scale ?lamentation of the laser beam caused by thermal self-focusing of radiation in the crater-con?ned plasma was evidenced by the presence of a microcrater relief on the bottom of the main crater. In translucent PMMA, with a penetration depth for UV light of several hundred micrometers, a long narrow channel of length 1 mm and diameter 30 μm was observed emerging from the crater vertex. Similar channels with a length-to-diameter aspect ratio of ～1000 were produced by a repeated-pulse KrF laser in PMMA and fused silica glass at an intensity of ～109 W cm?2. This channel formation is attributed to the effects of radiation self-focusing in the plasma and Kerr self-focusing in a partially transparent target material after shallow-angle re?ection by the crater wall. Experimental modeling of the initial stage of inertial con?nement fusion-scale direct-drive KrF laser interaction with subcritical coronal plasmas from spherical and cone-type targets using crater-con?ned plasmas seems to be feasible with increased laser intensity above 1014 W cm?2.
关键词： fused silica glass,UV radiation,PMMA,KrF laser,plasma,ICF,self-focusing
更新于2025-09-23 15:21:01
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2a??10???μm Mida??Infrared Fibera??Based Supercontinuum Laser Source: Experiment and Simulation
摘要： Mid-infrared supercontinuum (mid-IR SC) sources in the 2–20 μm molecular fingerprint region are in high demand for a wide range of applications including optical coherence tomography, remote sensing, molecular spectroscopy, and hyperspectral imaging. Herein, mid-IR SC generation is investigated in a cascaded silica-ZBLAN-chalcogenide fiber system directly pumped with a commercially available pulsed fiber laser operating in the telecommunications window at 1.55 μm. This fiber-based system is shown to generate a flat broadband mid-IR SC covering the entire range from 2 to 10 μm with several tens of mW of output power. This technique paves the way for low cost, practical, and robust broadband SC sources in the mid-IR without the requirement of mid-infrared pump sources or Thulium-doped fiber amplifiers. A fully realistic numerical model used to simulate the nonlinear pulse propagation through the cascaded fiber system is also described and the numerical results are used to discuss the physical processes underlying the spectral broadening in the cascaded system. Finally, recommendations are provided for optimizing the current cascaded system based on the simulation results.
关键词： soft-glass fibers,nonlinear optics and solitons,supercontinuum generation,chalcogenide fibers,fiber lasers,ZBLAN fibers
更新于2025-09-23 15:21:01