Electronic Military & Defense magazine was developed for engineers, program managers, project managers, and those involved in the design and development of electronic and electro-optic systems for military, defense, and aerospace applications.
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Technology New Optoelectronic Technologies Of Photonic Crystals And Metamaterials Newly developed optical technologies hold the promise of important advances in defense device technologies, including antennas, sensors, lasers, and the control of emission of radiation. By Arthur R. McGurn I n this article some of the basic properties of photonic crystal 1,2 and metamaterial 3-6 technologies are described, along with their possible applications as optical circuit elements or devices. These technologies are new developments in the field of optoelectronics, which focuses on developing optical component replacements of electronic components. Such replacements are of interest for a number of reasons: Signals in optical components may travel more rapidly than those in electronics components; switching relaxation times in optical systems may have lower fundamental limitations than in electronic systems; optical losses often are less than those in electronics; and optical components can operate with lower energy consumption than their electrical counterparts. 1-8 Such factors are at the heart of recent developments in all- optical computing, 9,10 nanocavity lasers, 1,2 photonic crystal fiber lasers, 1,2 and optical fibers and photonic circuits, 1,2,7,8 to name just a few technologies. Photonic crystals are dielectric materials of optical nanoscience. 1,2 They display periodic variation of their dielectric properties in space, making them the optical analogy of electronic semiconductors. In semiconductors, the periodic array of positive ions of the crystal structure changes the dynamics of the valence and conduction electrons, opening energy band gaps (referred to as stop bands) in which electrons with gap energies cannot propagate in the crystal. In photonic crystals, the periodic spatial variation of the optical dielectric medium opens energy band gaps (again referred to as stop bands) in the dynamics of light, for which light with energies in the energy gaps cannot propagate into the bulk of the photonic crystal. The important operating effects of photonic crystals are on light, with wavelengths comparable to the smallest spatial repeat distances of the periodic dielectric of the photonic crystal, so that diffractive effects dominate the physics. In general, photonic crystal applications and devices have focused on light at microwave to visible frequencies, exhibiting a variety of applications in the design of optical waveguides, 1,2 Fabry-Pérot laser cavities, 1,2 photonic crystal fibers, 11 optical transistors, 1,2,12,13 optical multiplexers, 14 optical switches, 1,2 and the modification of atomic decay rates. 1,2 Additional photonic crystal applications of specific interest to military and defense (M&D;) applications, include improving performance in lighting and solar energy-harvesting systems, 21 modulating the infrared emissivity of materials, so as to change their characteristic signatures, 22 and improving the radiation characteristics, including the directionality of antenna designs. 23 Applications of photonic crystal fibers related to M&D; are in designs for 11,14 fiber-optics communications, fiber lasers, nonlinear devices, power transmission, and physical, molecular, and biological sensors. 24 Metamaterials are engineered nanomaterials that are designed to respond, at a select set of frequencies of light, as homogeneous optical dielectric media. 2-6 They are important in the design of materials exhibiting negative index of refraction 2,5,6 and allow light to be refracted through a wider range of refractive angles than can be achieved using naturally occurring dielectric media. Negative index of refraction does not occur in materials that are found in nature, so that the newly engineered metamaterials extend the possibilities in optical design. For the most part, metamaterials have been limited to designs operating at microwave to visible frequencies. 2-6 There are a number of ways to engineer metamaterials, an early formulation being based on the inclusion of arrays of nanoscale features known as split-ring resonators to an otherwise homogeneous dielectric. 2-6 Metamaterials have applications in electromagnetic cloaking, 2-6,15 high-resolution lenses, 2-6,16 sensors, second-harmonic generation schemes, 2,17 antennae, 18 enhanced transmission effects through plasmonic surfaces, 19 and the simulation of optical effects in general relativity. 20 Additional applications of metamaterials for M&D; interests include the design of efficient and compact antennas 25,26,27 that can improve satellite communications 28 and the design of transmission Electronic Military & Defense Annual Resource, 6th Edition 24