Ahmed Sharkawy

Dispersion-based optical routing in photonic crystals

We present and experimentally validate self-collimation in planar photonic crystals as a new means of achieving structureless confinement of light in optical devices. We demonstrate the ability to arbitrarily route light by exploiting the dispersive characteristics of the photonic crystal. Propagation loss as low as 2.17 dB/mm is observed, and proposed applications of these devices are presented.

Multichannel wavelength division multiplexing with photonic crystals

A multichannel wavelength-division-multiplexing system consisting of a two-dimensional photonic crystal is proposed. The system consists of two parts, a waveguiding element, realized by defects in a photonic crystal, and frequency-selective elements, realized by photonic crystal microcavities. Simulations, performed with a two-dimensional finite-difference time-domain technique with a perfectly matched layer absorbing boundary condition, showed the ability to filter an incident pulse into six spectral channels with a FWHM of 2 nm.

Self-collimation in photonic crystal structures: a new paradigm for applications and device development

In this paper, we report on the development of the self-collimation phenomenon in photonic crystal structures for integrated optics applications. In addition, detailed numerical analysis, design procedures, fabrication and characterization techniques are included. Applications presented in this paper include: channelless waveguiding, orthogonal bending of light, tunable beam splitter, all-optical analog-to-digital converter, reconfigurable optical switch, chemical/gas sensor and a three-dimensional optical interconnect bus.

High-efficiency coupling structure for a single-line-defect photonic-crystal waveguide

We present the design and fabrication of a planar structure for coupling light from a multimode feed waveguide into a single-line-defect photonic-crystal waveguide. Finite-difference time-domain calculations predict a coupling efficiency of greater than 90%, and preliminary experimental results indicate successful coupling through a single-line-defect photonic-crystal waveguide. Device design, fabrication, and characterization are presented.

Dispersion-based beam splitter in photonic crystals

A novel implementation of a dispersion-based beam splitter in a photonic crystal (PhC) is proposed. The beam splitter consists of two periodic structures: a nonchannel dispersion-guiding region and a splitting structure operating inside the photonic bandgap. The dispersion-guiding PhC structure is used to route the optical wave by exploiting the dispersion properties of the lattice. An arbitrary power ratio between the output beams can be achieved by varying the parameters of the splitting structure. Within the studied range of splitting structures, high output power was observed and verified experimentally.

Analysis of splitters for self-collimated beams in planar photonic crystals

In this paper, we present methods for beam splitting in a planar photonic crystal, where the light is self-guided as dictated by the selfcollimation phenomenon. We present an analysis of a one-to-two and one-to-three beam splitter in a self-guiding photonic crystal lattice and validate our design and simulations with experimental results. Moreover, we present the first one-to-three splitter in a self-guiding planar photonic crystal. Additionally, we discuss the ability to tune the properties of these devices and present initial experimental results.

Photonic Crystal Structures and Applications: Perspective, Overview, and Development

In this paper, we present an overview of milestone achievements in the research and development of photonic crystal structures and their perspective applications. We highlight challenges in the analysis techniques, device design, efficient coupling techniques, and fabrication and characterization techniques for both planar and three-dimensional structures. We discuss extensively progress to date to overcome various aspects in the available modeling and simulation tools as well as the necessary fabrication procedures to produce functional photonic crystal structures and devices. Hence, the goal of the work presented in this paper is to present key building blocks, which will in turn facilitate the full utilization of the unique spatial and temporal properties of photonic crystal structures

Tunable photonic crystal microcavities

We present a method for tuning a photonic crystal microcavity by modulating the index of refraction of the lattice sites within and surrounding the microcavity. The index of refraction can be actively modulated after infiltrating anisotropic liquid crystals into a two-dimensional photonic crystal lattice of air cylinders in silicon. We analyze the Q-factors and resonance frequencies of a tunable photonic crystal microcavity by considering various methods of index modulation. These tunable cavities are incorporated in a channel drop filter to demonstrate their enhancement of wavelength division multiplexing photonic crystal applications.

Optimizing bending efficiency of self-collimated beams in non-channel planar photonic crystal waveguides.

In this paper, we propose a device to bend light in non-channel planar photonic crystal (PhC) waveguides using the self-collimation phenomenon. The mode distribution in a non-channel planar PhC waveguide is investigated in detail in order to help understand the proposed bending mechanism. Three-dimensional finite-difference time-domain simulations show an over 80% bending efficiency for a 90 degree bend. As the first proposal for bending light in a non-channel planar PhC waveguide, the presented device enables the application of routing in non-channel planar PhC waveguides.

Heterostructure photonic crystals: theory and applications

A hybrid structure combining square and hexagonal photonic crystal lattices is presented. This structure, which we refer to as heterostructure, offers the ability to tailor, optimize, and match the band structure of different lattices. The availability of heterostructures in photonic crystals opens abroad range of possibilities for optical device development. In particular, heterostructure photonic crystals are well suited for the application of optical beam splitting (Y coupler) and combining. Numerical experiments performed by use of the finite-difference time-domain method are shown to illustrate the device implemented in both unistructure and heterostructure lattices.