Micro sized electro-optical converter runs at up to 40Gbit/s

The converter consists of two parallel gold electrodes separated by a gap of about 0.1µm. A voltage applied to the electrodes is synchronised with the digital data. The gap between the electrodes is filled with an electro-optical polymer, whose refraction index changes as a function of the applied voltage. "A continuous beam of light from the silicon waveguide excites electromagnetic surface waves – surface plasmons, or SP – in the gap," said Argishti Melikyan, lead author of a paper published in Nature Photonics. "As a result of the voltage applied to the polymer, the phase of the SP is modulated. At the end of the device, the modulated SPs enter the exit silicon waveguide in the form of a modulated beam of light. In this way, the data bits are encoded in the phase of the light." The modulator uses infrared light with wavelengths ranging from 1480 to 1600nm; typically used in broadband optical fibre networks. KIT researchers say the device can be produced using established cmos processes, supporting integration into other devices. Christian Koos, from KIT's Helmholtz International Research School of Teratronics, said: "Hundreds of plasmonic modulators might fit on a chip and data rates in the range of terabits per second might be reached."