Published in 2009
Department of Electrical & Computer Engineering Assistant Professor Luca Dal Negro was recently awarded $479,997 in funding for his research proposal, “Deterministic Aperiodic Structures for On-chip Nanophotonics and Nanoplasmonics Device Applications.” The grant, which spans four years, was awarded by the US Air Force Office of Scientific Research.
Understanding the role of aperiodic order in optical systems provides unique opportunities for the engineering of light dispersion, density of states fluctuations, radiation patterns, frequency spectra and localized field states in complex non-periodic photonic-plasmonic nanostructures created by simple mathematical rules and amenable to predictive theories. The specific objective of this research project is to design, explore and engineer a novel class of Si-based, photonic-plasmonic planar structures capable of providing ultra broadband (0.4μm-1.8μm) enhancement of nanoscale-localized optical fields and nonlinear processes in metal-dielectric Deterministic Aperiodic Nano Structures (DANS). Differently from conventional crystal structures, which are limited by translational invariance symmetry, the proposed research approach focuses on the design and fabrication of on-chip localized field states by Fourier-space engineering in photonic-plasmonic nanostructures with controllable degree of aperiodic order and non-crystallographic point symmetries (i.e. high degree of rotational invariance, statistical symmetries, multi-fractal scaling).
In this project, we will engineer DANS in the form of metal-dielectric nano-particles, nano-pillars, and nano-holes arrays fabricated on Si substrates by Electron Beam Lithography (EBL). All the proposed structures are amenable to inexpensive pattern replication on the wafer scale by using nano-imprint lithographic techniques, thus reducing the costs associated to EBL nanofabrication. DANS structures will be fabricated with varying degree of structural complexity (ranging from quasi-periodicity to pseudo-randomness) combined with statistical and higher-order rotational symmetries, not yet explored in the field of photonics. These structures will be designed using a number of rigorous analytical and numerical techniques including multi-particle scattering theories (GMT, T-matrix theory, Discrete Dipole Approximations, FDTD, Finite Elements) and will be experimentally characterized using dark-field scattering, micro-Raman, time-resolved emission and non-linear optical spectroscopy.
In relation to novel device synthesis and characterization, this project will explore the science and technological opportunities of DANS in relation to: (a) broadband enhancement and control of far-fields and radiative processes; (b) modification of non-linear optical responses in quantum dots; (c) engineering of angle-insensitive, broadband scattering substrates for plasmon-enhanced solar cells; (d) engineering of strongly-coupled photonic-plasmonic optical sensors.