the use of smart pixel devices, which combine electronic processing circuitry with optical inputs and/or outputs and can be integrated into two-dimensional arrays. Researchers are investigating several approaches to applying smart pixels in high-speed switching, as interconnects, and in flat-panel display applications.

Electro-optical Polymers

The increase in optical-fiber capacity also creates the need to speed information in and out of the fibers. One new approach to speeding this information flow uses polymers containing organic chromophores, which are molecules involved in color. Evidence suggests that embedding chromophores can yield electro-optical polymers that have higher speeds—as high as 100 gigahertz—and require lower voltages than present-day electronic modulators. However, chromophores tend to align in ways that reduce the effect of an applied field, a problem that needs resolution.

Researchers are also exploring holography to create three-dimensional photonic crystals for use in ultrasmall waveguides and other optical-communications uses. So far, however, the thickness of the crystal layers is limited to about 30 micrometers, and more advances in processing will be needed to obtain the larger photonic crystals needed for communications applications.

Significant improvements in key photonic devices seem a certainty in the next decade, including in-fiber optical filters (known as fiber Bragg gratings), infiber amplifiers, and fiber lasers. Fiber Bragg gratings, for example, are the building blocks of wavelength division multiplexing and essential elements for the next generation of all-optical switches and networks. In-fiber amplifiers depend on doping the core of optical fibers with rare-earth ions, and refining the doping process should optimize various amplifier designs. Fiber lasers can sustain high power densities and can currently generate pulses of 100 femtoseconds. The development of polymer lasers holds significant potential for speeding communications.

One challenge to developing new photonic devices is that models currently used to characterize materials require unrealistic computer time. As a result, prototype devices often must be built for testing. A great need exists for new algorithms to address issues such as simulation, analysis, alignment tolerance, and increasing the yields of photonic components.

Superconductors

In recent years, applications of high-temperature superconductors have moved beyond the realm of laboratory sensors. The U.S. Navy, for example, has awarded a contract for the design of a 25,000-horsepower superconductor motor to power its next generation of destroyers. The ability of these superconductors to transmit electricity with essentially zero resistance will in and of itself guarantee



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