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1. Nonlinear Optical Transmission in WSe2 Induced by Intense THz Fields

   https://doi.org/10.1364/FIO.2022.FTh1C.3  

   Bradley, Alden N.; Guay, Viela; Thorp, Spencer G.; Zhang, Yue; van der Zande, Arend M.; Graham, Matthew; Lee, Yun-Shik (January 2022, Optica Publishing Group)

   In WSe2 intense THz fields are found to enhance transmission at 400 nm, while reducing it at 800 nm. The differential transmission is proportional to the field amplitude. The nonlinear responses are fast, yet non-adiabatic. 

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2. Spatially resolved measurements of ballistic and total transmission in microscale tissue samples from 450 nm to 1624 nm

   https://doi.org/10.1364/BOE.441844  

   Mok, Aaron_T; Shea, Jamien; Wu, Chunyan; Xia, Fei; Tatarsky, Rose; Yapici, Nilay; Xu, Chris (December 2021, Biomedical Optics Express)

   We built a simple and versatile setup to measure tissue ballistic and total transmission with customizable wavelength range, spatial resolution, and sample sizes. We performed ballistic transmission and total transmission measurements of overlying structures from biological samplesex vivo. We obtained spatially resolved transmission maps to reveal transmission heterogeneity from five microscale tissue samples:Danionellaskin, mouse skull bone, mosquito cuticle, wasp cuticle, and rat dura over a wide spectral range from 450 nm to 1624 nm at a spatial resolution of ∼25µm for ballistic transmission measurements and ∼50µm for total transmission measurements. We expect our method can be straightforwardly applied to measuring the transmission of other samples. The measurement results will be valuable for multiphoton microscopy. The total transmission of a sample is important for the collection of multiphoton excited fluorescence and the assessment of laser-induced sample heating. The ballistic transmission determines the excitation power at the focus and hence the fluorescence signal generation. Therefore, knowledge of ballistic transmission, total transmission, and transmission heterogeneity of overlying structures of animals and organs are essential to determine the optimal excitation wavelength and fluorophores for non-invasive multiphoton microscopy. 

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3. Electron scattering at interfaces in epitaxial W(001)–Mo(001) multilayers

   https://doi.org/10.1063/5.0223176  

   Shen, Poyen; Gall, Daniel (August 2024, Journal of Applied Physics)

   Epitaxial W–Mo multilayers are employed as a model system to demonstrate how resistivity measurements parallel to metal–metal interfaces can be used to quantify the specific interface resistance without sub-10-nm patterning that would be required for direct transport measurements across the interface. 50-nm-thick epitaxial multilayer stacks containing 2–60 individual W(001) and Mo(001) layers are deposited on MgO(001) substrates and their resistivity ρ measured as a function of superlattice period Λ at 293 and 77 K. The measured room temperature ρ increases from 7.10 to 8.62 μΩ cm with decreasing Λ = 50–1.7 nm, which is attributed to the increasing electron-interface scattering. The semiclassical Fuchs–Sondheimer model for surface scattering dramatically overestimates the resistivity, which is attributed to coherent electron transmission across multiple interfaces. A new Boltzmann transport model treats each interface as a boundary condition where electrons either scatter diffusely or traverse without momentum loss with a probability T for the first encountered interface and with 100% transmission at subsequent interfaces until they are relaxed by a bulk scattering event. This model has a single unknown parameter T, which becomes the fitting parameter for experimental data analysis, yielding a temperature-independent T = 0.8 ± 0.1 and a corresponding contact resistance at the W(001)–Mo(001) interface of 2.6 × 10−16 Ω m2. 

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4. a -axis YBa2Cu3O7− x /PrBa2Cu3O7− x /YBa2Cu3O7− x trilayers with subnanometer rms roughness

   https://doi.org/10.1063/5.0034648  

   Suyolcu, Y_Eren; Sun, Jiaxin; Goodge, Berit_H; Park, Jisung; Schubert, Jürgen; Kourkoutis, Lena_F; Schlom, Darrell_G (February 2021, APL Materials)

   We demonstrate a-axis YBa2Cu3O7−x/PrBa2Cu3O7−x/YBa2Cu3O7−x trilayers grown on (100) LaAlO3 substrates with improved interface smoothness. The trilayers are synthesized by ozone-assisted molecular-beam epitaxy. The thickness of the PrBa2Cu3O7−x layer is held constant at 8 nm, and the thickness of the YBa2Cu3O7−x layers is varied from 24 nm to 100 nm. X-ray diffraction measurements show all trilayers to have >97% a-axis content. The rms roughness of the thinnest trilayer is <0.7 nm, and this roughness increases with the thickness of the YBa2Cu3O7−x layers. The thickness of the YBa2Cu3O7−x layers also affects the transport properties: while all samples exhibit an onset of the superconducting transition at and above 85 K, the thinner samples show wider transition widths, ΔTc. High-resolution scanning transmission electron microscopy reveals coherent and chemically sharp interfaces and that growth begins with a cubic (Y,Ba)CuO3−x perovskite phase that transforms into a-axis oriented YBa2Cu3O7−x as the substrate temperature is ramped up. 

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5. Visible emission properties of melt-gown Dy-doped CsPbCl3 and KPb2Cl5 crystals,

   U. Hommerich, S. Uba (July 2020, Optical materials express)

   null (Ed.)

   We report results of the optical properties of Dy-doped CsPbCl3 and KPb2Cl5 bulk crystals for potential applications in yellow solid-state laser development. The crystals were synthesized from purified starting materials and melt-grown by vertical Bridgman technique. Optical transmission measurements revealed characteristic absorption bands from intra-4f transitions of Dy3+ ions. Direct optical excitation at 455 nm (6H15/2 -> 4I15/2) resulted in dominant yellow emission bands at 575 nm from the 4F9/2 excited state of Dy3+ ions. In addition, both crystals exhibited weaker emission lines in the blue (483 nm) and red (670 nm) regions. The peak emission-cross sections for the yellow transition (4F9/2 -> 6H13/2) were determined to be 0.22 x 10^20 cm2 for Dy: CsPbCl3 (lpeak = 576.5 nm) and 0.59 x 10^20 cm2 for Dy: KPb2Cl5 (lpeak = 574.5 nm). The spectral properties and decay dynamics of the 4F9/2 excited state were evaluated within the Judd-Ofelt theory to predict total radiative decay rates, branching ratios, and emission quantum efficiencies. 

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