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1. Rapid multiplex ultrafast nonlinear microscopy for material characterization

   https://doi.org/10.1364/OE.472054  

   Purz, Torben_L; Hipsley, Blake_T; Martin, Eric_W; Ulbricht, Ronald; Cundiff, Steven_T (November 2022, Optics Express)

   We demonstrate rapid imaging based on four-wave mixing (FWM) by assessing the quality of advanced materials through measurement of their nonlinear response, exciton dephasing, and exciton lifetimes. We use a WSe₂monolayer grown by chemical vapor deposition as a canonical example to demonstrate these capabilities. By comparison, we show that extracting material parameters such as FWM intensity, dephasing times, excited state lifetimes, and distribution of dark/localized states allows for a more accurate assessment of the quality of a sample than current prevalent techniques, including white light microscopy and linear micro-reflectance spectroscopy. We further discuss future improvements of the ultrafast FWM techniques by modeling the robustness of exponential decay fits to different spacing of the sampling points. Employing ultrafast nonlinear imaging in real-time at room temperature bears the potential for rapid in-situ sample characterization of advanced materials and beyond. 

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2. Progress toward photon-pair efficiency optimization using four-wave mixing in few-mode fibers

   https://doi.org/10.1364/AO.558793  

   Montazeri, Seyedehnajmeh; Esmaeelpour, Mina (May 2025, Applied Optics)

   Intermodal four-wave mixing (FWM) process in few-mode fibers (FMFs) could be utilized for entangled photon-pair generation. Previous studies mainly performed in single-mode fibers suffered from the significant Raman scattering background from the glass fiber. Therefore, the instantaneous Raman and FWM effects would compete; this could be avoided in FMFs if the modal dispersion is larger than the Raman gain spectra. Utilizing two pumps in different modes in FMFs will generate photon pairs in various modes. Here, we study the effect of pump spectral separation on the intermodal FWM power and bandwidth using a seeding technique. It is concluded that the further the pumps and intermodal FWM idler and signal are from each other spectrally, the smaller the photon efficiency and larger the bandwidth. Experimental results for two FMFs of different differential mode group delay values are presented. 

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3. A multi-layer platform for low-loss nonlinear silicon photonics

   https://doi.org/10.1063/1.5115234  

   MacFarlane, Neil; Kossey, Michael_R; Stroud, Jasper_R; Foster, Mark_A; Foster, Amy_C (November 2019, APL Photonics)

   We demonstrate four-wave mixing (FWM) interactions in a-Si:H waveguides in a multilayer integrated silicon photonic chip. The a-Si:H waveguides are accessed through interlayer couplers from waveguides composed of SiNx. The interlayer couplers achieve a coupling of 0.51 dB loss per transition at the target wavelength of 1550 nm. We observe greater idler power extraction and conversion efficiency from the FWM interaction in the interlayer-coupled multilayer waveguides than in single-material waveguides. 

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4. Can supplementary pollen feeding reduce varroa mite and virus levels and improve honey bee colony survival?

   https://doi.org/10.1007/s10493-020-00562-7  

   DeGrandi-Hoffman, Gloria; Corby-Harris, Vanessa; Chen, Yanping; Graham, Henry; Chambers, Mona; Watkins deJong, Emily; Ziolkowski, Nicholas; Kang, Yun; Gage, Stephanie; Deeter, Megan; et al (December 2020, Experimental and Applied Acarology)

   Abstract Varroa destructor is an ectoparasitic mite of immature and adult honey bees that can transmit several single-stranded RNA viruses to its host. Varroa reproduce in brood cells, and mite populations increase as colonies produce brood in spring and summer. Mite numbers also can sharply rise, particularly in the fall, by the migration of varroa into hives on foragers. Colonies with high levels of varroa and viruses often die over the winter. Feeding colonies pollen might keep virus levels low and improve survival because of the positive effects of pollen on immunity and colony growth. We compared varroa and virus levels and overwinter survival in colonies with (fed) and without (unfed) supplemental pollen. We also measured the frequency of capturing foragers with mites (FWM) at colony entrances to determine its relationship to varroa and virus levels. Colonies fed supplemental pollen were larger than unfed colonies and survived longer. Varroa populations and levels of Deformed wing virus (DWV) rose throughout the season, and were similar between fed and unfed colonies. The growth of varroa populations was correlated with FWM in fed and unfed colonies, and significantly affected DWV levels. Increasing frequencies of FWM and the effects on varroa populations might reduce the positive influence of supplemental pollen on immune function. However, pollen feeding can stimulate colony growth and this can improve colony survival. 

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5. Coarse woody debris accelerates the decomposition of deadwood inputs across temperate forest

   https://doi.org/10.5061/dryad.0rxwdbs39  

   Bradford, Mark; Veen, Ciska; Bradford, Ella; Covey, Kristofer; Crowther, Thomas; Fields, Nicholas; Frankson, Paul; Gonzalez-Rivero, Javier; Jevon, Fiona; Kuebbing, Sara; et al (January 2022, Dryad)

   Wood decomposition is regulated by multiple controls, including climate and wood traits, that vary at local to regional scales. Yet decomposition rates differ dramatically when these controls do not. Fungal community dynamics are often invoked to explain these differences, suggesting that knowledge of ecosystem properties that influence fungal communities will improve understanding and projection of wood decomposition. We hypothesize that deadwood inputs decompose faster in forests with higher stocks of downed coarse woody material (CWM) because CWM is a resource from which lignocellulolytic fungi rapidly colonize new inputs. To test this hypothesis, we measure decomposition of 1,116 pieces of fine woody material (FWM) of five species, incubated for 13 to 49 months at five locations spanning 10°-latitude in eastern U.S. forest. We place FWM pieces near and far from CWM across observational transects and experimental common gardens. Soil temperature positively affects location-level mean decomposition rates, but these among-location differences are smaller than within-location variation in decomposition. Some of this variability is caused by CWM, where FWM pieces next to CWM decompose more rapidly. These effects are greater with time of incubation and lower initial wood density of FWM. The effect size of CWM is of the same relative magnitude as for the known controls of temperature, deadwood density and diameter. Abundance data for CWM is available for many forests and hence may be an ecosystem variable amenable for inclusion in decomposition models. Our findings suggest that conservation efforts to rebuild depleted CWM stocks in temperate forests may accelerate decomposition of fresh deadwood inputs. Please see the associated manuscript for the Methods. All files are in .txt or .csv format and so can be opened with common, open-source software. The file named 'README_BradfordetalCWMproximity.txt' describes the uploaded files. 

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