Semiconductor Surface Studies

Contains an introduction, reports on two research projects and a list of publications.Joint Services Electronics Program Grant DAAH04-95-1-003

Theoretical design of photonic crystal devices for integrated optical circuits

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 2000.Includes bibliographical references (p. 139-143).In this thesis we investigate novel photonic crystal devices that can be used as building blocks of all-optical circuits. We contrast the behavior of light in photonic crystal systems and in their traditional counterparts. We exhibit that bends in photonic crystals are able to transmit light with over 90% efficiency for large bandwidths and with 100% efficiency for specific frequencies. In contrast to traditional waveguides, bound states in photonic crystal waveguides can also exist in constrictions and above the cutoff frequency. We discuss how to lower reflections encountered when photonic crystal waveguides are terminated, both in an experimental setup as well as in numerical simulations. We show that light can be very efficiently coupled into and out of photonic crystal waveguides using tapered dielectric waveguides. In time-domain simulations of photonic crystal waveguides, spurious reflections from cell edges can be eliminated by terminating the waveguide with a Bragg reflector waveguide. We demonstrate novel lasing action in two-dimensional photonic crystal slabs with gain media, where lasing occurs at saddle points in the band structure, in contrast to one-dimensional photonic crystals. We also design a photonic crystal slab with organic gain media that has a TE-like pseudogap. We demonstrate that such a slab can support a high-Q defect mode, enabling low threshold lasing, and we discuss how the quality factor depends on the design parameters. We also propose to use two dimensional photonic crystal slabs as directionally efficient free-space couplers. We draft methods to calculate the coupling constant both numerically and analytically, using a finite-difference time-domain method and the volume current method with a Green's function approach, respectively.by Attila Mekis.Ph.D

MOLDING THE FLOW OF LIGHT

A new class of materials, called photonic crystals, affects a photon’s properties in much the same way that a semiconductor affects an electron’s properties. The ability to mold and guide light leads naturally to novel applications in several fields, including optoelectronics and telecommunications. The authors present an introductory survey of the basic concepts and ideas, including results for never before possible photon phenomena

Solid State Theory Meets Photonics: The Curious Optical Properties Of Photonic Crystals

The past decades have seen dramatic advances in microstructuring technology. Today, a wide variety of structures with feature sizes ranging from a couple of micrometers all the way down to a few tens of nanometers are routinely fabricated with precision better than ten nanometers. In addition to these improvements in fabrication quality, the variety of materials that can be processed is growing continuously. These advances in materials science are paralleled by the development of novel and improvement of existing laser sources that allows one to generate electromagnetic fields with previously unattainable energy densities as well as temporal and spatial coherences. Bringing together advanced microfabrication technologies with sophisticated laser systems lies at the heart of Nano-Photonics: The control over the flow of light on length scales of the wavelength of light itself through microstructured optical materials (“photonic metamaterials”) with carefully designed properties