Novel resonant and light-guiding phenomena in photonics

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 100-109).We investigate theoretically five novel resonant and light-guiding photonics phenomena. First, we develop a universal coupled mode theory (CMT) treatment of the freespace scattering of waves from resonant objects. This analytical framework very accurately models the scattering and absorption cross sections, as long as the resonant scatterer has spherical/cylindrical symmetry, or is sufficiently smaller than the resonant wavelength of the incident wave. We apply it to study the scattering of light from spherically symmetrical resonant objects and atoms, and also the neutron scattering off nuclei. Then, we propose an efficient weakly-radiative Wireless Energy Transfer (WET) scheme between two identical classical resonant objects, strongly coupled to an intermediate one having the same resonance frequency. The transfer mechanism, analyzed by CMT, relies on the adiabatic evolution of a dark eigenstate of the 3-object system. We explore its performance in various parameter regimes, and illustrate it by witricity-type WET between resonant inductively-coupled capacitively-loaded metallic loops. Third, we develop an analytical CMT model for the electric field generated by an arbitrary polarization source in a general photonic structure (that could involve loss, gain and/or nonlinearities). Based on this model, we investigate the criteria for enhancing the efficiency of nonlinear effects, and produce efficient terahertz sources. The results, validated by Finite-Difference Time-Domain (FDTD) calculations, suggest that this approach could potentially be a substitute for the more numerically intensive FDTD method. Next, we propose a 2D PhC structure that supports super-collimation over a large frequency range. We theoretically and numerically investigate the collimation mechanism in this 2D structure, in comparison to that of two other frequently used related PhC structures. We also point out the potential importance of this structure in designing super-collimation-based devices for monochromatic and polychromatic light. Finally, we present numerical simulations of anisotropic multilayers that strongly discriminate certain incidence angles of light, over a broad range of frequencies and irrespective of polarization. Such systems could improve the efficiency of solar cells.by Rafif E. Hamam.Ph.D

Efficient weakly-radiative wireless energy transfer: An EIT-like approach

Inspired by a quantum interference phenomenon known in the atomic physics community as electromagnetically induced transparency (EIT), we propose an efficient weakly radiative wireless energy transfer scheme between two identical classical resonant objects, strongly coupled to an intermediate classical resonant object of substantially different properties, but with the same resonance frequency. The transfer mechanism essentially makes use of the adiabatic evolution of an instantaneous (so called “dark”) eigenstate of the coupled 3-object system. Our analysis is based on temporal coupled mode theory (CMT), and is general enough to be valid for various possible sorts of coupling, including the resonant inductive coupling on which witricity-type wireless energy transfer is based. We show that in certain parameter regimes of interest, this scheme can be more efficient, and/or less radiative than other, more conventional approaches. A concrete example of wireless energy transfer between capacitively-loaded metallic loops is illustrated at the beginning, as a motivation for the more general case. We also explore the performance of the currently proposed EIT-like scheme, in terms of improving efficiency and reducing radiation, as the relevant parameters of the system are varied.U.S. Department of EnergyDARPAArmy Research OfficeNational Science Foundatio

Angular photonic band gap

We present detailed numerical simulations of a class of material systems that strongly discriminate light based primarily on the angle of incidence, over a broad range of frequencies, and independent of the polarization. Unique properties of these systems emerge from exploring photonic crystals whose constituents have an anisotropic dielectric response.National Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (Grant no. DMR-0819762)United States. Dept. of Energy. Office of Basic Energy Sciences (S3TEC grant no. DE-SC0001299)Massachusetts Institute of Technology. Energy Initiativ

Broadband super-collimation in a hybrid photonic crystal structure

We propose a two dimensional (2D) photonic crystal (PhC) structure that supports super-collimation over a large frequency range (over 4 times that of a traditional square lattice of holes). We theoretically and numerically investigate the collimation mechanism in our 2D structure, in comparison to that of two other frequently used related PhC structures. We also point out the potential importance of our proposed structure in the design of super-collimation-based devices for both monochromatic and polychromatic light