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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Observation of Branched Flow of Light
摘要： The evolution of coherent waves in two-dimensional systems with a random potential can give rise to an interesting phenomenon known as Branched Flow. In this process, a wave scatters from a weak random potential with correlation length longer than the wavelength, and forms focused channels that keep dividing as the wave propagates, creating a pattern resembling the branches of a tree. This phenomenon was observed for electrons [1–3], for a specific example of microwaves [4] and for ocean waves [5], but thus far never for light at optical frequencies. Furthermore, the statistical features of branched flow were predicted theoretically but were never observed in any experimental system. Here, we present the first observation of branched flow in optics, prove that the experiments represent branched flow, and study the statistical features. In our experiments, we couple an optical beam to a thin liquid soap film and observe its evolution within this thin membrane. The light experiences scattering from thickness variations in the soap film, which acts as a two-dimensional medium with a random potential. The beam propagates and scatters from the random thickness variations, forming focused branches that keep dividing, ending up in a pattern that resembles the branches of a tree, as shown in Fig.1a. To view the thickness variations directly, we construct a white light microscope illuminating the thin soap film from above, and observe the colorful map shown in Fig. 1b. The colors in Fig. 1b are true colors, and they emerge due to the reflection of white light from the thin soap film, indicating the local thickness (Fig.1c). The colors are mapped to the thickness map shown in Fig.1d, and from that to a two-dimensional map of effective refractive index landscape.The formation of the branches is the result of the appearance of caustics in the random field, following the variations in the refractive index. The theory of Branched Flow [6] gave rise to several predictions, most of which have never been studied in experiments. One example for such a prediction is the distance to the first caustic, (cid:1856)(cid:2868), which was predicted by never observed. From the experiments, we extract (cid:1856)(cid:2868) using the Scintillation Index – the variance of the intensity of the fluctuations. It is a convenient notion, because caustics give rise to the highest intensity fluctuations, hence the scintillation index is a measure of the steepness of the caustics. The first caustic is the steepest one; hence, it corresponds to the peak in the scintillation index shown in Fig. 1e. The distance to the first caustic is ~1 in units of (cid:2022)(cid:2035)(cid:2879)(cid:2870)/(cid:2871), correlation length and potential strength, as shown in that figure. In this regime, the phenomenon of branching of caustics perfectly matches the model of branched flow. To support our experiments, we also carry out simulations (Fig. 1e), of a coherent beam launched into a random 2D potential constructed from the actual experimental image. The beam splits and divides by the potential variations, displaying branched flow as in experiments. From the experiments, we extract additional statistical features of branched flow that were predicted but have never been observed, such as the statistics of the extreme events. In addition, we also study branched flow in curved space (where the soap membrane is curved) and the nonlinear behavior occurring when the light exerts forces on the soap bubble.
关键词： random potential,Branched Flow,caustics,optical frequencies,Scintillation Index
更新于2025-09-11 14:15:04
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Fiber Optic and Atmospheric Optical Communication || Transmission of Information Data in Optical Channels: Atmospheric and Fiber Optics
摘要： The chapter discusses the transmission of information data in optical channels, focusing on atmospheric and fiber optics. It highlights the challenges posed by atmospheric effects on wave propagation, including attenuation, optical signal amplitude, and phase scintillations caused by atmospheric turbulence. The chapter also explores the impact of these phenomena on the data stream parameters, such as bit error rate (BER) and signal-to-noise ratio (SNR), and proposes methods to mitigate these effects to achieve high performance in optical communication links.
关键词： atmospheric turbulence,bit error rate,optical communication,spectral efficiency,signal-to-noise ratio,scintillation,fading,Ricean K-factor,fiber optics,multipath channel
更新于2025-09-11 14:15:04
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Photon detection system designs for the Deep Underground Neutrino Experiment
摘要： The Deep Underground Neutrino Experiment (DUNE) will be a premier facility for exploring long-standing questions about the boundaries of the standard model. Acting in concert with the liquid argon time projection chambers underpinning the far detector design, the DUNE photon detection system will capture ultraviolet scintillation light in order to provide valuable timing information for event reconstruction. To maximize the active area while maintaining a small photocathode coverage, the experiment will utilize a design based on plastic light guides coated with a wavelength-shifting compound, along with silicon photomultipliers, to collect and record scintillation light from liquid argon. This report presents recent preliminary performance measurements of this baseline design and several alternative designs which promise signi?cant improvements in sensitivity to low-energy interactions.
关键词： Neutrino detectors,Photon detectors for UV, visible and IR photons (solid-state),Scintillators and scintillating ?bres and light guides,Noble liquid detectors (scintillation, ionization, double-phase)
更新于2025-09-11 14:15:04
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Optical and luminescent properties of Pr-doped Li2O MgO Al2O3SiO2 glasses
摘要： A high conversion e?ciency is a key factor for phosphor applications. Because the number of studies on the 5d–4f emissions of Pr3+ in oxide glasses has been limited, it is worth examining the relationship between the luminescence properties of Pr3+ and the chemical composition of the glass. Herein, we demonstrate the luminescence properties of Pr3+-doped aluminosilicate glasses. Although the internal quantum e?ciency is not as high as that of conventional Ce3+-doped glasses, a faster decay (on the order of nanoseconds) is attractive for many di?erent applications. An emissions band can be observed under X-ray irradiation, which di?ers signi?cantly from photoluminescence. Although the Pr3+–P-codoped samples exhibit higher quantum e?ciency than P-free glass owing to a blue shift of the optical absorption edge, the e?ect of P doping was not observed during X-ray induced scintillation or in the pulse height spectra under 252Cf irradiation.
关键词： Photoluminescence,Glass,Phosphorus,Praseodymium,Luminescence,Scintillation
更新于2025-09-11 14:15:04
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Luminescence properties of Ce3+ and Eu2+ doped M3MgSi2O8 (M = Ca, Sr) phosphors for potential detecting applications
摘要： A series of phosphors M3–xLnxMgSi2O8 (M = Ca, Sr; Ln = Ce, Eu; x = 0.005, 0.01, 0.03, 0.05, 0.07, 0.10, 0.15) were synthesized. The luminescence properties in the vacuum ultraviolet-ultraviolet visible spectral range and the X-ray excited radioluminescence were investigated in detail. The results reveal that the M3–xLnxMgSi2O8 (M = Ca, Sr; Ln = Ce, Eu) phosphors exhibit typical broad excitation and emission bands, which are ascribed to the 4f–5d transitions of the Ce3+ and Eu2+ ions. Finally, X-ray excited luminescence (XEL) spectra were measured to evaluate the possibility of Sr3MgSi2O8:Ce3+ and Sr3MgSi2O8:Eu2+ as scintillation materials.
关键词： Scintillation materials,M3MgSi2O8,Luminescence properties
更新于2025-09-11 14:15:04
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The $$\hbox {Na}_2\hbox {W}_2\hbox {O}_7$$Na2W2O7 crystal: a crystal scintillator for dark matter search experiment
摘要： A single crystal of Na2W2O7 (NWO) was grown by a low-thermal-gradient Czochralski technique (LTG-CZ). The scintillation properties of the crystal were evaluated for the ?rst time as a potential material for dark matter search experiments. The luminescence and scintillation characteristics of the crystal were studied at room temperature and low temperatures by using a light-emitting diode (LED) and a 90Sr beta source. The luminescence and scintillation light yield at 10 K were signi?cantly higher than those at room temperature. The crystal showed higher light yield at 10 K than a CaMoO4 (CMO) crystal. The decay time of the crystal was investigated at temperatures between 10 and 300 K. The sensitivity to spin-independent weakly interacting massive particle-nucleon interactions based on 10 kg (2 months) and 50 kg (12 months) data for the NWO crystal detectors was estimated by a simulated experiment using the standard halo model. The luminescence, scintillation, and sensitivity results revealed that the NWO crystal is a promising candidate for a dark matter search experiment in the near future.
关键词： dark matter search,Na2W2O7 crystal,cryogenic temperatures,luminescence,scintillation properties
更新于2025-09-10 09:29:36
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Effect of linear energy transfer on the scintillation properties of Ce:Gd3Al2Ga3O12
摘要： We analyzed the scintillation properties of Ce:Gd3Al2Ga3O12 (GAGG), which are dependent on linear energy transfer (LET). The rise in the scintillation temporal profiles was slow at high LET, whereas the decay did not significantly depend on LET. The slow rise at high LET could be explained as follows. Competition among multiple excited states for energy transfer to a nearby Ce3+ ion led to failure in energy transfer for some of the excited states. Subsequent competition occurred among the residual excited states for energy transfer to the Ce3+ ions located far from the original position of the excited states, followed by quenching.
关键词： Excitation density,Energy transfer,Quenching,Scintillation
更新于2025-09-10 09:29:36
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Scintillation properties of Ce-doped SrF2-Al2O3-B2O3 glasses
摘要： xCeF3-doped (30-x)SrF2-20Al2O3-50B2O3 glasses (x = 0.1, 1.0, 5.0 and 10 mol%) were synthesized by the conventional melt quenching method, and then characterizations for scintillator applications were performed. Regarding the photoluminescence (PL) properties, the glasses show a broad emission band around 360 nm under excitation of approximately 325 nm, and the decay time constant is several tens of nano-seconds. From the results, the origin is attributed to the 5d → 4f transitions of Ce3+. As scintillation properties, the X-ray induced scintillation spectra and decay time constants are reasonably consistent with the PL. Among the present glass samples, the scintillation intensity is the highest when doped with 1% Ce. The light yields of the 1% Ce-doped glass shows 240 photons/MeV under 57Co 122 keV γ-ray exposure. The light yields were derived as relative values to that of commercial GS20 glass scintillator. This is the ?rst report on the scintillation light yields of Ce-doped SrF2-Al2O3-B2O3 glasses. Furthermore, the materials also exhibit thermally stimulated luminescence (TSL) properties with a major glow peak around 80 °C, and the sensitivity to radiation dose is as low as 0.1 mGy for the 0.1% and 1.0% Ce-doped glasses with a good linearity con?rmed to 100 mGy.
关键词： Photoluminescence,Oxy?uoride glasses,TSL,Scintillation,Aluminoborate glasses
更新于2025-09-10 09:29:36
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226Ra determination in complex samples using liquid scintillation counting
摘要： A co-precipitation method followed by a liquid–liquid extraction and liquid scintillation counting is proposed to get low 226Ra detection limits when measuring complex samples. The sensitivity of the method is determined with an analysis of interfering agents on it. The ion-exchange followed by alpha spectrometry is also described and an analysis of the advantages and disadvantages of both methods is carried out. Then, a comparison between both methods, considering also time and cost analysis, is realised. Conclusions show that both methods provide similar values for uncertainties, critical values and chemical yields when similar sample size and measuring times are chosen.
关键词： Liquid scintillation counting,226Ra activity,Complex sample,Alpha-spectrometry
更新于2025-09-10 09:29:36
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Temperature Gradient Designing and Optical Properties of SrI2 and SrI2:Eu Crystals Grown by Edge-Defined Film-Fed Growth (EFG) Method
摘要： In this work, SrI2 and SrI2:Eu5% single crystals with size of ?10 9 60 mm3 and ?10 9 30 mm3 were successfully grown by edge-de?ned ?lm-fed growth (EFG) method. In the crystal growth process, the crack and turbidity of the crystal were solved by designing a temperature ?eld, thereby optimizing crystal quality and obtaining crack-free crystals. X-ray diffraction analysis was performed on the grown crystals, and the optical properties of these crystals have been investigated at room temperature. Under the excitation of ultraviolet (UV) light, the crystals exhibit a single luminescence peak centered at 435 nm (kex = 350 nm), and the photoluminescence (PL) decay time is 0.594 ls. In addition, the designed temperature ?eld also provides a reference value for other crystals grown by EFG method.
关键词： Crystal growth,temperature ?eld,scintillation materials,optical properties
更新于2025-09-10 09:29:36