The ability to manipulate wave transport phenomena and to enhance light-matter interactions using silicon-compatible, dispersion-engineered materials, epsilon-near-zero (ENZ) platforms, and complex photonic media with desired radiation properties is at the heart of current nanophotonics and metamaterials technologies. For example, the dramatic enhancement of the nonlinear optical interactions of transparent conductive oxides (TCOs) provides unique opportunities to engineer novel optoelectronic devices with order-of-unity (non-perturbative) refractive index changes on sub-picosecond time scales for dynamically tunable metasurfaces, broadband optical modulators, optical switching, and time-varying photonics applications on the chip. Moreover, recent progress in the theory, inverse-design, fabrication, and characterization of high-refractive index, low-loss, diffractive optical elements and dielectric nanostructures with tailored disorder and hyperuniform geometries established novel strategies to engineer ultra-compact imaging devices and nanostructures with desired wave transport and localization properties over targeted spectral- and spatial-frequency bandwidths.
In this talk, I will discuss our work on the design, fabrication, and characterization of highly nonlinear Si-compatible materials and nanostructures based on the indium tin oxide (ITO) platform with tunable ENZ responses across the near-infrared spectral range. In particular, I will address the non-perturbative Kerr-type optical nonlinearity of fabricated materials and resonant devices driven by the excitation of optical Tamm states. Building on this platform, I will illustrate the potential of topologically optimized high-Q nonlinear dielectric nanocavities for extreme sub-wavelength field confinement potentially enabling photon-blockade and strong-coupling effects. Next, I will present our recent work on the inverse-design of ultra-compact and multifunctional spectroscopic imaging devices based on diffractive optical networks (a-DONs) and the adjoint optimization of high-refractive index functionalized scattering arrays for imaging and radiation engineering on the chip. Finally, I will provide a perspective on anomalous diffusion and light localization in multifractal photonic environments that encode the characteristic multiscale complexity of number-theoretic sequences and algebraic number fields beyond random lasing device applications.
1) A. Capretti, Y. Wang, N. Engheta, L. Dal Negro “Enhanced third-harmonic generation in Si-compatible epsilon-near-zero indium tin oxide nanolayers”, Opt. Lett., Vol. 40, Issue 7, 1500-1503, (2015)
2) W. Britton, F. Sgrignuoli, L. Dal Negro, “Structure-dependent optical nonlinearity of indium tin oxide”, Appl. Phys. Lett. 120, 101901 (2022)
3) W. Britton, Y. Chen, F. Sgrignuoli, L. Dal Negro, “Phase-Modulated Axilenses As Ultracompact Spectroscopic Tools”, ACS Photonics, 7, 10, 2731–2738 (2020)
4) W. Britton, Y. Chen, F. Sgrignuoli, L. Dal Negro, “Compact Dual-Band Multi-Focal Diffractive Lenses”, Laser Photonics Rev. 15, 2000207 (2021)
5) Y. Chen, Y. Zhu, W. A. Britton, and L. Dal Negro, “Inverse design of ultracompact multi-focal optical devices by diffractive neural networks”, Opt. Lett., Vol. 47, No. 11, 2842-2845, (2022).
6) Y. Zhu, Y. Chen, and L. Dal Negro, “Design of ultracompact broadband focusing spectrometers based on diffractive optical networks”, Opt. Lett., Vol. 47, No. 24, 6309-6312, (2022).
7) S. Gorsky; W. A. Britton; Y. Chen, J. Montaner; A. Lenef, M. Raukas, L. Dal Negro, “Engineered hyperuniformity for directional light extraction”, APL Photonics 4, 110801 (2019)
8) F. Sgrignuoli, S. Gorsky, W. A. Britton, R. Zhang, F. Riboli, and L. Dal Negro, “Multifractality of light in photonic arrays based on algebraic number theory” Communications Physics, 3, 106 (2020).
9) Y. Chen, F. Sgrignuoli, Y. Zhu, T. Shubitidze, and L. Dal Negro, “Enhanced wave localization in multifractal scattering media”, Phys. Rev. B 107, 054201 (2023).
10) L. Dal Negro, “Waves in Complex Media”, Cambridge University Press (2022).
Luca Dal Negro received both the Laurea in physics, cum laude, in 1999 and the Ph.D. degree in semiconductor physics from the University of Trento (Italy) in 2003. After his Ph.D. he joined MIT as a post-doctoral research associate. Since January 2006 he is a faculty member in the Department of Electrical and Computer Engineering at Boston University (BU). He is currently a Full Professor in the Department of Electrical and Computer Engineering, a member of the Boston University Photonics Center and has appointments in the Department of Physics and the Division of Material Science at Boston University. Prof. Dal Negro manages and conducts research projects on light transport and localization in complex media, nano-optics and plasmonics, optical materials, and metamaterials. He is an editor of the journal MRS Communications, published jointly by the Materials Research Society and Springer, and was associate editor of the European Physical Journal (EPJ) Plus, published by Springer-Verlag for the European Physical Society. He has authored and co-authored over 250 technical papers, 16 book chapters, 2 books, and has a google scholar h-index=63 and more than 15,800 citations. His research work resulted in several Awards including the Early Career Research Excellence Award and the National Science Foundation (NSF) Career Award. Prof. Dal Negro has been elected Fellow of the Optical Society of America (currently OPTICA) “For his numerous contributions in the theoretical and experimental aspects of wave interaction with aperiodic nanostructures”.