All Publications


  • High-Q nanophotonics: sculpting wavefronts with slow light NANOPHOTONICS Barton, D., Hu, J., Dixon, J., Klopfer, E., Dagli, S., Lawrence, M., Dionne, J. 2021; 10 (1): 83–88
  • Driving energetically unfavorable dehydrogenation dynamics with plasmonics. Science (New York, N.Y.) Sytwu, K. n., Vadai, M. n., Hayee, F. n., Angell, D. K., Dai, A. n., Dixon, J. n., Dionne, J. A. 2021; 371 (6526): 280–83

    Abstract

    Nanoparticle surface structure and geometry generally dictate where chemical transformations occur, with higher chemical activity at sites with lower activation energies. Here, we show how optical excitation of plasmons enables spatially modified phase transformations, activating otherwise energetically unfavorable sites. We have designed a crossed-bar Au-PdH x antenna-reactor system that localizes electromagnetic enhancement away from the innately reactive PdH x nanorod tips. Using optically coupled in situ environmental transmission electron microscopy, we track the dehydrogenation of individual antenna-reactor pairs with varying optical illumination intensity, wavelength, and hydrogen pressure. Our in situ experiments show that plasmons enable new catalytic sites, including dehydrogenation at the nanorod faces. Molecular dynamics simulations confirm that these new nucleation sites are energetically unfavorable in equilibrium and only accessible through tailored plasmonic excitation.

    View details for DOI 10.1126/science.abd2847

    View details for PubMedID 33446555

  • High quality factor phase gradient metasurfaces. Nature nanotechnology Lawrence, M., Barton, D. R., Dixon, J., Song, J., van de Groep, J., Brongersma, M. L., Dionne, J. A. 2020

    Abstract

    Dielectric microcavities with quality factors (Q-factors) in the thousands to billions markedly enhance light-matter interactions, with applications spanning high-efficiency on-chip lasing, frequency comb generation and modulation and sensitive molecular detection. However, as the dimensions of dielectric cavities are reduced to subwavelength scales, their resonant modes begin to scatter light into many spatial channels. Such enhanced scattering is a powerful tool for light manipulation, but also leads to high radiative loss rates and commensurately low Q-factors, generally of order ten. Here, we describe and experimentally demonstrate a strategy for the generation of high Q-factor resonances in subwavelength-thick phase gradient metasurfaces. By including subtle structural perturbations in individual metasurface elements, resonances are created that weakly couple free-space light into otherwise bound and spatially localized modes. Our metasurface can achieve Q-factors >2,500 while beam steering light to particular directions. High-Q beam splitters are also demonstrated. With high-Q metasurfaces, the optical transfer function, near-field intensity and resonant line shape can all be rationally designed, providing a foundation for efficient, free-space-reconfigurable and nonlinear nanophotonics.

    View details for DOI 10.1038/s41565-020-0754-x

    View details for PubMedID 32807879

  • Dynamic Focusing with High-Quality-Factor Metalenses. Nano letters Klopfer, E. n., Lawrence, M. n., Barton, D. R., Dixon, J. n., Dionne, J. A. 2020

    Abstract

    Metasurface lenses provide an ultrathin platform in which to focus light, but weak light-matter interactions limit their dynamic tunability. Here we design submicron-thick, ultrahigh quality factor (high-Q) metalenses that enable dynamic modulation of the focal length and intensity. Using full-field simulations, we show that quality factors exceeding 5000 can be generated by including subtle, periodic perturbations within the constituent Si nanoantennas. Such high-Q resonances enable lens modulation based on the nonlinear Kerr effect, with focal lengths varying from 4 to 6.5 μm and focal intensities decreasing by half as input intensity increases from 0.1 to 1 mW/μm2. We also show how multiple high-Q resonances can be embedded in the lens response through judicious placement of the perturbations. Our high-Q lens design, with quality factors 2 orders of magnitude higher than existing lens designs, provides a foundation for reconfigurable, multiplexed, and hyperspectral metasurface imaging platforms.

    View details for DOI 10.1021/acs.nanolett.0c01359

    View details for PubMedID 32497434

  • Evaluation of a Silicon Sr-90 Betavoltaic Power Source SCIENTIFIC REPORTS Dixon, J., Rajan, A., Bohlemann, S., Coso, D., Upadhyaya, A. D., Rohatgi, A., Chu, S., Majumdar, A., Yee, S. 2016; 6

    Abstract

    Betavoltaic energy converters (i.e., β-batteries) are attractive power sources because of their potential for high energy densities (>200 MWh/kg) and long duration continuous discharge (>1 year). However, conversion efficiencies have been historically low (<3%). High efficiency devices can be achieved by matching β-radiation transport length scales with the device physics length scales. In this work, the efficiency of c-Si devices using high-energy (>1 MeV) electrons emitted from (90)Sr as a power source is investigated. We propose a design for a >10% efficient betavoltaic device, which generates 1 W of power. A Varian Clinac iX is used to simulate the high-energy electrons emitted from (90)Sr, and a high efficiency c-Si photovoltaic cell is used as the converter. The measured conversion efficiency is 16%. This relatively high value is attributed to proper length scale matching and the generation of secondary electrons in c-Si by the primary β-particles.

    View details for DOI 10.1038/srep38182

    View details for Web of Science ID 000388995400001

    View details for PubMedCentralID PMC5131278

  • Sr Betavoltaic Power Source. Scientific reports Dixon, J., Rajan, A., Bohlemann, S., Coso, D., Upadhyaya, A. D., Rohatgi, A., Chu, S., Majumdar, A., Yee, S. 2016; 6: 38182-?

    Abstract

    Betavoltaic energy converters (i.e., β-batteries) are attractive power sources because of their potential for high energy densities (>200 MWh/kg) and long duration continuous discharge (>1 year). However, conversion efficiencies have been historically low (<3%). High efficiency devices can be achieved by matching β-radiation transport length scales with the device physics length scales. In this work, the efficiency of c-Si devices using high-energy (>1 MeV) electrons emitted from (90)Sr as a power source is investigated. We propose a design for a >10% efficient betavoltaic device, which generates 1 W of power. A Varian Clinac iX is used to simulate the high-energy electrons emitted from (90)Sr, and a high efficiency c-Si photovoltaic cell is used as the converter. The measured conversion efficiency is 16%. This relatively high value is attributed to proper length scale matching and the generation of secondary electrons in c-Si by the primary β-particles.

    View details for DOI 10.1038/srep38182

    View details for PubMedID 27905521

    View details for PubMedCentralID PMC5131278

  • Investigation of hydrogen induced fluorescence in C-60 and its potential use in luminescence down shifting applications NANOSCALE Teprovich, J. A., Washington, A. L., Dixon, J., Ward, P. A., Christian, J. H., Peters, B., Zhou, J., Giri, S., Sharp, D. N., Velten, J. A., Compton, R. N., Jena, P., Zidan, R. 2016; 8 (44): 18760-18770

    View details for DOI 10.1039/c6nr05998h

    View details for Web of Science ID 000387858700023