All Publications


  • Theory for Twisted Bilayer Photonic Crystal Slabs. Physical review letters Lou, B., Zhao, N., Minkov, M., Guo, C., Orenstein, M., Fan, S. 2021; 126 (13): 136101

    Abstract

    We analyze scattering properties of twisted bilayer photonic crystal slabs through a high-dimensional plane wave expansion method. The method is applicable for arbitrary twist angles and does not suffer from the limitations of the commonly used supercell approximation. We show strongly tunable resonance properties of this system which can be accounted for semianalytically from a correspondence relation to a simpler structure. We also observe strongly tunable resonant chiral behavior in this system. Our work provides the theoretical foundation for predicting and understanding the rich optical physics of twisted multilayer photonic crystal systems.

    View details for DOI 10.1103/PhysRevLett.126.136101

    View details for PubMedID 33861130

  • Determining the optimal learning rate in gradient-based electromagnetic optimization using the Shanks transformation in the Lippmann-Schwinger formalism OPTICS LETTERS Boutami, S., Zhao, N., Fan, S. 2020; 45 (3): 595–98

    Abstract

    In gradient-based optimization of photonic devices, within the overall design parameter space, one iteratively performs a line search in a one-dimensional subspace as spanned by the search direction. While the search direction can be efficiently determined with the adjoint variable method, there has not been an efficient algorithm that determines the optimal learning rate that controls the distance one moves along the search direction. Here we introduce an efficient algorithm of determining the optimal learning rate, using the Shanks transformation in the Lippmann-Schwinger formalism. Our approach can determine very accurately the optimal learning rates at each epoch, with only a modest increase of computational cost. We show that this approach can significantly improve the figure of merits of the final structure, as compared to conventional methods for estimating the learning rate.

    View details for DOI 10.1364/OL.379375

    View details for Web of Science ID 000510869500001

    View details for PubMedID 32004260

  • Penetration Depth Engineering in Plasmonic Metafilms for Enhanced Reflection and Confinement Zhao, N., Williamson, I. D., Zhao, Z., Boutami, S., Fan, S., IEEE IEEE. 2020
  • Near-complete violation of Kirchhoff's law of thermal radiation with a 0.3 T magnetic field OPTICS LETTERS ZHAO, B., Shi, Y., Wang, J., Zha, Z., Zhao, N., Fan, S. 2019; 44 (17): 4203–6

    Abstract

    The capability to overcome Kirchhoff's law of thermal radiation provides new opportunities in energy harvesting and thermal radiation control. Previously, design towards demonstrating such capability requires a magnetic field of 3 T, which is difficult to achieve in practice. In this work, we propose a nanophotonic design that can achieve such capability with a far more modest magnetic field of 0.3 Tesla, a level that can be achieved with permanent magnets. Our design uses guided resonance in low-loss dielectric gratings sitting on a magneto-optical material, which provides significant enhancement on the sensitivity to the external magnetic field.

    View details for DOI 10.1364/OL.44.004203

    View details for Web of Science ID 000483918900029

    View details for PubMedID 31465363

  • Penetration Depth Reduction with Plasmonic Metafilms ACS PHOTONICS Zhao, N. Z., Williamson, I. D., Zhao, Z., Boutami, S., Fan, S. 2019; 6 (8): 2049–55
  • Accelerating adjoint variable method based photonic optimization with Schur complement domain decomposition OPTICS EXPRESS Zhao, N. Z., Boutami, S., Fan, S. 2019; 27 (15): 20711–19
  • High Reflection from a One-Dimensional Array of Graphene Nanoribbons ACS PHOTONICS Zhao, N., Zhao, Z., Williamson, I. D., Boutami, S., Zhao, B., Fan, S. 2019; 6 (2): 339–44
  • High Reflection from a One-Dimensional Array of Graphene Nanoribbons Zhao, N., Zhao, Z., Williamson, I. D., Boutami, S., Zhao, B., Fan, S., IEEE IEEE. 2019
  • Accelerating convergence of iterative solution of finite difference frequency domain problems via schur complement domain decomposition OPTICS EXPRESS Zhao, N., Verweij, S., Shin, W., Fan, S. 2018; 26 (13): 16925–39