Boston Chapter of the IEEE Photonics Society

Abstract:  The control of light-matter interactions in complex photonic structures without translational invariance offers the ultimate potential for the creation and manipulation of light states. Unlike periodically arranged structures (photonic crystals), deterministically generated aperiodic and fractal metal/dielectric photonic structures show unique light localization and transport properties related to an unprecedented degree of structural complexity. However, unlike aperiodic random media, they can be generated according to simple mathematical rules and therefore possess perfect long-range order, enabling reproducible on-chip fabrication of novel optical devices.  Recently, deterministically-generated one dimensional aperiodic dielectric structures  have been fabricated by stacking together layers of different dielectric constants, A and B, according to simple mathematical rules, such as the Fibonacci or the Thue-Morse sequences, which encode a fascinating complexity displayed by their Fourier transforms.

Here we propose for the first time the use of metal/dielectric 2D structures based on aperiodic order for the engineering of electromagnetic hot spots on chip-size devices. The approach is based on the excitation of collective plasmon (SP) resonances in non-periodic, deterministic chips which can be fabricated by electron-beam lithography. Periodic one-dimensional SPs waveguides have been proposed and electromagnetic plasmon coupling in 1D structures has been intensively investigated in the last 5 years.  

However, despite their large potential for nanophotonics applications, metal/dielectric one-dimensional (1D) and two-dimensional (2D) aperiodic structures have not been investigated so far.  Based on both Finite-Difference-Time-Domain (FDTD) and Finite Element analysis, we report on the design and nanofabrication of planar plasmonic devices based on surface plasmon-polariton (SPP) localization and electromagnetic coupling. Our analysis shows that large field enhancement effects can be achieved in deterministic aperiodic structures within deep sub-wavelength regions (hot electromagnetic spots).  The use of non-periodic, deterministic 1D and 2D metal nano-particle arrays represent a convenient approach to manipulate enhanced local fields on chip-scale devices which can have a large impact for active nanophotonics applications.

Biography:  Luca Dal Negro received both the Laurea in physics, summa cum laude, in 1999 and the Ph.D. degree in semiconductor physics from the University of Trento, Italy, in 2003. After his Ph.D., in 2003 he joined MIT as a post doctoral associate. Since January 2006 he is Assistant Professor in the Department of Electrical and Computer Engineering at Boston University.

He manages and conducts research projects on silicon-based photonic materials and devices, plasmonic structures and semiconductor laser spectroscopy. His main focus is currently on quantum dots spectroscopy, complex photonic crystals structures and nano-photonics. He has authored and coauthored more than 50 technical articles.