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Optical physics

Optical physics

High-speed switching at low voltages

07 Apr 2000

A new low-voltage device that can convert electric pulses into optical signals at rates greater than 100 gigahertz (GHz) could find applications in the telecommunications and computer industries. Yongqiang Shi from TACAN Corporation in California and colleagues made the device by altering the shape of organic electro-optic molecules called chromophores that are embedded in a polymer matrix. The new shapes minimized the electric field interactions between the chromophores, thus enhancing the electro-optic properties of the device (Science 288 119).

Converting electrical signals into optical pulses is one of the speed ‘bottlenecks’ in current telecommunications systems. To reach high data speeds, a series of electro-optic devices called modulators, all operating at different wavelengths, are used. The most common modulators are based on a lithium niobate compound, but they require high voltages (5 V) to work. The devices also have limited gain and high noise levels.

The new polymer modulators only require 1 volt to work, which reduces energy consumption and heating in the device. Although lithium niobate modulators currently only operate at 2.5 GHz, a new technique based on so-called Bragg gratings is expected to reduce the voltage needed to operate them, and also increase the transmission rate to 100 GHz. However, the fact that the modulators still generate heat and cannot be integrated directly onto silicon chips could leave a gap in the market for the new polymer devices.


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