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1. Focused-beam optical potentials for cold atoms near an atom chip

   https://doi.org/10.1364/JOSAB.595759  

   Zanders, Alan; Du, Shengwang (August 2026, Journal of the Optical Society of America B)

   Precise alignment of an optical potential with a micrometer-scale magnetic trap near an atom chip is technically challenging compared with free-space systems. We investigate a double-well potential created by a focused, blue- detuned laser beam superimposed on an atom-chip magnetic trap for manipulating cold 87Rb atoms. The measured separation of atomic clouds in the double well serves as a sensitive indicator of the laser focus: the separation reaches a minimum when the beam is aligned with the center of the magnetic trap. We develop a theoretical model for the combined magnetic and optical potentials and the resulting atomic motion, and validate its predictions using Monte Carlo simulations over a broad range of trap frequencies, barrier heights, and temperatures. Both the model and simulations show that optimal alignment corresponds to the minimum observable separation between the two atomic clouds. Parameter scans further reveal that stronger axial confinement and lower temperatures enhance the detectability of this minimum, providing a practical optical-alignment method for atom-chip systems in which direct beam characterization near the surface is difficult. 

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2. An efficient 2D array of blue-detuned optical traps

   Graham, Trent; Xiaoyu, Jiang; Poole, Cody; Sun, Yuan; Lichtman, Martin; Saffman, Mark (May 2018, Bulletin American Physical Society, DAMOP 2018)

   We demonstrate a 2D lattice of blue-detuned optical traps which uses laser power efficiently, is tolerant to perturbations in beam alignment, and is insensitive to interferometric phases. Blue traps have several advantages over red traps despite requir- ing a more complicated beam geometry. Since atoms in a blue trap sit at an intensity minimum, Stark shift noise and site-to-site calibrations are minimized. However, constructing a blue lattice which efficiently con- verts laser power into trap depth, is challenging. For example, a lattice of bottle beams is inefficient because neighboring sites are separated by two walls, limiting the number of traps that can be formed. An array of tightly spaced Gaussian beams is a more efficient blue trap, but the trap potentials are susceptible to alignment perturbations. We demonstrate an array which uses diffractive optical elements to create a cross-hatched pattern of lines in the focal region where the atoms are trapped in up to 121 sites. This "line array" is almost twice as efficient as the Gaussian beam array and is more resilient to perturbations in beam alignment. 

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3. Scaling of silicon nanoparticle growth in low temperature flowing plasmas

   https://doi.org/10.1063/5.0062255  

   Lanham, Steven J.; Polito, Jordyn; Shi, Xuetao; Elvati, Paolo; Violi, Angela; Kushner, Mark J. (October 2021, Journal of Applied Physics)

   Low temperature plasmas are an emerging method to synthesize high quality nanoparticles (NPs). An established and successful technique to produce NPs is using a capacitively coupled plasma (CCP) in cylindrical geometry. Although a robust synthesis technique, optimizing or specifying NP properties using CCPs, is challenging. In this paper, results from a computational investigation for the growth of silicon NPs in flowing inductively coupled plasmas (ICPs) using Ar/SiH4 gas mixtures of up to a few Torr are discussed. ICPs produce more locally constrained and quiescent plasma potentials. These positive plasma potentials produce an electrostatic trap for negatively charged NPs, which can significantly extend the residence time of NPs in the plasma, which in turn provides a controllable period for particle growth. The computational platforms used in this study consist of a two-dimensional plasma hydrodynamics model, a three-dimensional nanoparticle growth and trajectory tracking model, and a molecular dynamics simulation for deriving reactive sticking coefficients of silane radicals on Si NPs. Trends for the nanoparticle growth as a function of SiH4 inlet fraction, gas residence time, energy deposition per particle, pressure, and reactor diameter are discussed. The general path for particle synthesis is the trapping of small NPs in the positive electrostatic potential, followed by entrainment in the gas flow upon reaching a critical particle size. Optimizing or controlling NP synthesis then depends on the spatial distribution of plasma potential, the density of growth species, and the relative time that particles spend in the electrostatic trap and flowing through higher densities of growth species upon leaving the trap. 

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4. 88Sr+ ion trap apparatus for generating 408 nm photons

   https://doi.org/10.1063/5.0288146  

   Lin, Jianlong; Cieszynski, Mari; Christopherson, William; Khan, Darman; Li, Lintao; Goldschmidt, Elizabeth; DeMarco, Brian (January 2026, Review of Scientific Instruments)

   We describe a 88Sr+ ion trap apparatus with the capability to produce high-quality 408 nm photons aimed at distributed quantum computing and networking applications. This instrument confines ion chains using a surface electrode trap with a two-dimensional magneto-optical trap as an atomic source. Several laser systems spanning 400–1100 nm are used to achieve high-fidelity state preparation and readout. Photons are produced via the decay of an exited state, which is accessed using a custom 408 nm laser system that produces 150 ps optical pulses using non-linear photonics. We demonstrate single-photon production through a Hanbury Brown–Twiss measurement for one to six ions. 

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5. Scalable trapping of single nanosized extracellular vesicles using plasmonics

   https://doi.org/10.1038/s41467-023-40549-7  

   Hong, Chuchuan; Ndukaife, Justus C. (December 2023, Nature Communications)

   Abstract Heterogeneous nanoscale extracellular vesicles (EVs) are of significant interest for disease detection, monitoring, and therapeutics. However, trapping these nano-sized EVs using optical tweezers has been challenging due to their small size. Plasmon-enhanced optical trapping offers a solution. Nevertheless, existing plasmonic tweezers have limited throughput and can take tens of minutes for trapping for low particle concentrations. Here, we present an innovative approach called geometry-induced electrohydrodynamic tweezers (GET) that overcomes these limitations. GET generates multiple electrohydrodynamic potentials, allowing parallel transport and trapping of single EVs within seconds. By integrating nanoscale plasmonic cavities at the center of each GET trap, single EVs can be placed near plasmonic cavities, enabling instant plasmon-enhanced optical trapping upon laser illumination without detrimental heating effects. These non-invasive scalable hybrid nanotweezers open new horizons for high-throughput tether-free plasmon-enhanced single EV trapping and spectroscopy. Other potential areas of impact include nanoplastics characterization, and scalable hybrid integration for quantum photonics. 

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