{"id":80,"date":"2019-05-29T12:07:14","date_gmt":"2019-05-29T16:07:14","guid":{"rendered":"https:\/\/www.bu.edu\/nano\/?page_id=80"},"modified":"2019-12-04T17:03:10","modified_gmt":"2019-12-04T22:03:10","slug":"research-areas-projects","status":"publish","type":"page","link":"https:\/\/www.bu.edu\/nano\/research-areas-projects\/","title":{"rendered":"Research Areas &#038; Projects"},"content":{"rendered":"<h2 style=\"text-align: center;\"><span style=\"color: #000080;\"><em>Waves in Complex Photonic Media<\/em><\/span><\/h2>\n<p class=\"style42\"><img loading=\"lazy\" width=\"714\" height=\"482\" class=\"wp-image-157 aligncenter\" alt=\"\" src=\"\/nano\/files\/2019\/06\/Picture1-636x429.jpg\" srcset=\"https:\/\/www.bu.edu\/nano\/files\/2019\/06\/Picture1-636x429.jpg 636w, https:\/\/www.bu.edu\/nano\/files\/2019\/06\/Picture1-768x518.jpg 768w, https:\/\/www.bu.edu\/nano\/files\/2019\/06\/Picture1-1024x691.jpg 1024w\" sizes=\"(max-width: 714px) 100vw, 714px\" \/><\/p>\n<p class=\"style42\" style=\"text-align: justify;\">The control of nanomaterials, structures and optical fields lies at the heart of the current nanotechnology revolution and offers unprecedented opportunities to engineer novel functional elements on the nanoscale. Dal Negro\u2019s group research activities are focused on the nanofabrication, linear\/nonlinear optical characterization and electromagnetic modeling of metal-dielectric nanomaterials and nanostructures for on-chip nanophotonics applications. In particular, we develop efficient nanoscale light sources and laser structures based on the cost-effective silicon technology and we study the behavior of optical fields confined in complex media such as fractals, quasi-crystals and more complex deterministic aperiodic systems. Our combined computational and experimental activities aim at advancing the fields of silicon photonics and nanoplasmonics by demonstrating novel concepts and device structures for on-chip optical sensing, light emission, energy conversion and thin-film solar cell technology.<br \/>\nIn particular, we fabricate semiconductor and optical bio-polymers nanostructures, metal nanoparticle arrays and we investigate their linear and nonlinear optical properties. In addition, using electron-beam nanolithography we design and fabricate large-scale, resonant arrays of nanoparticles and we study their photonic-plasmonic behavior in relation to light-matter coupling, nonlinear optical response and the engineering of multiple light scattering and radiative processes (light emission) on the nanoscale. Moreover, our experimental research activities are assisted by rigorous electrodynamical modeling of complex photonic media based on efficient analytical models and numerical approaches to multiple scattering theories. The recent mathematical methods of deep learning and artificial neural networks are utilized in our group for the design of multiple scattering media with novel functionalities.<\/p>\n<ul class=\"style43\">\n<li class=\"style42\"><span style=\"color: #0000ff;\">Computationally-Guided Design of Energy Efficient Electronic Materials (CDE3M), ARmy Research Laboratory<\/span><\/li>\n<\/ul>\n<h3>Artificial Neural Networks (ANN) for photonics modeling and design<\/h3>\n<p style=\"text-align: justify;\">In this research activity we utilize state-of-the-art developments in machine learning and artificial neural networks for the design and modeling of complex photonic media and metamaterial structures. Specifically, we\u00a0employ the emerging paradigm of physics-informed neural networks (PINNs)<br \/>\nfor the solution of representative inverse scattering problems in photonic metamaterials and nano-optics technologies. For more information read our <a href=\"http:\/\/arxiv.org\/abs\/1912.01085\">recent paper\u00a0<\/a><\/p>\n<h3>Wave localization in aperiodic photonic media<\/h3>\n<p><img loading=\"lazy\" width=\"371\" height=\"360\" class=\"alignnone wp-image-166\" alt=\"\" src=\"\/nano\/files\/2019\/06\/web-wavelocalization-636x617.jpg\" srcset=\"https:\/\/www.bu.edu\/nano\/files\/2019\/06\/web-wavelocalization-636x617.jpg 636w, https:\/\/www.bu.edu\/nano\/files\/2019\/06\/web-wavelocalization-768x745.jpg 768w, https:\/\/www.bu.edu\/nano\/files\/2019\/06\/web-wavelocalization-1024x993.jpg 1024w\" sizes=\"(max-width: 371px) 100vw, 371px\" \/><\/p>\n<p style=\"text-align: justify;\">Understanding wave transport and localization phenomena in aperiodic optical media\u00a0provides opportunities to tailor their optical density of states and to enhance light-matter interactions\u00a0for the engineering of novel active photonic devices. For instance,\u00a0the study of multiple light scattering<br \/>\nin random media led to the demonstration of random lasers with both uniform and correlated\u00a0disorder, as well as to remarkable advances in optical imaging and spectroscopy. Our research focuses on the design and engineering of complex photonic media that are deterministic in nature. A representative example of a\u00a0 deterministic aperiodic scattering array that plays a significant role in our research is shown in the Scanning Electron Microscope (SEM) picture above, which displays a Vogel spiral array of SiN nanopillars. More generally, deterministic structures with aperiodic though long-range ordered\u00a0distributions of scattering potentials have a long history in the electronics and optics communities due to\u00a0significant advantages in design and compatibility with standard fabrication technologies compared to\u00a0random systems.\u00a0These structures manifest unique spectral characteristics that lead to physical\u00a0properties that cannot be found in either periodic or uniform random media, such as multifractal\u00a0density of eigenstates with varying degrees of spatial localization, known as critical modes,\u00a0anomalous photon transport regimes, and distinctive wave localization transitions. In the last 15 years our group has developed a large number of aperiodic deterministic systems for photonics applications that include light sources and lasers, optical biosensors, thin-film photovoltaic cells, and non-linear optical elements.<\/p>\n<p style=\"text-align: justify;\">Recently we introduced a novel class of aperiodic photonic systems\u00a0that leverage the distinctive aperiodic order, unpredictability, and complexity that is present in\u00a0number theory.\u00a0Examples include the aperiodic distribution of prime numbers and their algebraic field generalizations,\u00a0the almost-periodicity characteristic of arithmetic functions, aperiodic primitive roots and quadratic\u00a0residue sequences, the intricate behavior of Dirichlet L-functions (which include the Riemann\u2019s zeta\u00a0function), and the distribution of binary digits in Galois fields, just to name a few. Moreover, we recently demonstrated and engineered novel photonic structures that manifest the distinctive\u00a0aperiodic order of elliptic curves and the associated discrete logarithm problem over finite fields.\u00a0 Our work not only\u00a0underlines the importance of structural correlations in elliptic curve-based structures for photonics\u00a0technology but additionally provides an optics-driven approach to rapidly identify the potential\u00a0vulnerabilities of modern EC-based cryptosystems. In our research we combine the\u00a0interdisciplinary methods of point patterns spatial statistics and spectral graph theory\u00a0 with the rigorous Green\u2019s matrix solution\u00a0of the multiple wave scattering problem for electric and magnetic dipoles and we systematically explore\u00a0the spectral and light scattering properties of novel deterministic aperiodic structures with enhanced\u00a0light-matter coupling for nanophotonics and metamaterials applications to imaging and spectroscopy.<\/p>\n<h3>Fractional calculus and photon transport in complex media<\/h3>\n<p style=\"text-align: justify;\">In this research project we use the\u00a0recently developed mathematical tools of fractional calculus to describe anomalous transport phenomena in the presence of memory and long-range spatial\u00a0correlations in aperiodic complex photonic media.\u00a0 In particular we work with <strong>fractional<\/strong><br \/>\n<strong>transport equations<\/strong> with space and time derivatives of arbitrary (non-integer) order. These correspond to integro-differential operators<br \/>\nwith power-law kernels that naturally account for space correlations and time memory effects established when\u00a0wave excitations are multiply scattered in strongly non-homogeneous environments. Lately we applied these methods to random lasers with incoherent feedback, which are described within\u00a0the diffusion approximation, and we extended the traditional Letokhov laser model by considering fractional<br \/>\ndiffusion equations of arbitrary order, including distributed-order (DO) fractional diffusion processes.\u00a0Our comprehensive analytical and numerical analysis of fractional\u00a0photon transport regimes in deterministic aperiodic\u00a0 and random gain media demonstrates the relevance of engineered photon sub-diffusion\u00a0processes to realize novel lasers and active device structures with strongly reduced amplification threshold<br \/>\nand footprint.<\/p>\n<h3>Novel resonant materials for metaphotonics<\/h3>\n<p style=\"text-align: justify;\">Metaphotonics is the convergence of plasmonics, metamaterials, and nonlinear optics on a single chip. In this context, we are developing<br \/>\nalternative plasmonic materials compatible with complementary\u00a0metal-oxide-semiconductor (CMOS) technology and with tunable optical<br \/>\nresponses, reduced optical losses, and low refractive indices that provide exciting opportunities for future nonlinear and active metaphotonic device applications. Refer to our publications page for additional details on these activities.<\/p>\n<h3>Plasmonics and metamaterials<\/h3>\n<p style=\"text-align: justify;\">We work on the design, synthesis, and experimental characterization of resonant metallo-dielectric nanostructures for plasmonics and metamaterials technology. In particular, we are interested in developing novel concepts that leverage strong modifications of electromagnetic fields in nanoscale environments for optical sensing and spectroscopy applications.\u00a0Refer to our publications page for additional details on these activities.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Waves in Complex Photonic Media The control of nanomaterials, structures and optical fields lies at the heart of the current nanotechnology revolution and offers unprecedented opportunities to engineer novel functional elements on the nanoscale. Dal Negro\u2019s group research activities are focused on the nanofabrication, linear\/nonlinear optical characterization and electromagnetic modeling of metal-dielectric nanomaterials and nanostructures [&hellip;]<\/p>\n","protected":false},"author":16034,"featured_media":0,"parent":0,"menu_order":4,"comment_status":"closed","ping_status":"closed","template":"page-templates\/no-sidebars.php","meta":[],"_links":{"self":[{"href":"https:\/\/www.bu.edu\/nano\/wp-json\/wp\/v2\/pages\/80"}],"collection":[{"href":"https:\/\/www.bu.edu\/nano\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.bu.edu\/nano\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.bu.edu\/nano\/wp-json\/wp\/v2\/users\/16034"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bu.edu\/nano\/wp-json\/wp\/v2\/comments?post=80"}],"version-history":[{"count":10,"href":"https:\/\/www.bu.edu\/nano\/wp-json\/wp\/v2\/pages\/80\/revisions"}],"predecessor-version":[{"id":220,"href":"https:\/\/www.bu.edu\/nano\/wp-json\/wp\/v2\/pages\/80\/revisions\/220"}],"wp:attachment":[{"href":"https:\/\/www.bu.edu\/nano\/wp-json\/wp\/v2\/media?parent=80"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}