In order to exchange data faster and more energy efficient between electronic chips, are compact optical transmission possibilities of great interest. A component of this is the Mach-Zehnder modulator (MZM) adapted to convert electronic signals into optical signals. Researchers at the KIT and ETH now have a plasmonic MZM with only 12.5 micrometers in length developed the digital electrical converted to optical signals at a rate of up to 108 gigabits per second, and this presented in the journal Nature Photonics.
tenth the thickness of a hair
In the current publication, an MZM is presented, the is only 12.5 microns long, or about one-tenth the thickness of a hair. It consists of two arms in which a respective electro-optical modulator is located. Each modulator consists of a metal-insulator-metal waveguide having an approximately 80 nanometer wide filled with electro-optical plastic gap and gold-side walls, the function at the same time as electrodes. To the electrodes, a voltage that is modulated in time with the digital data. The electro-optical plastic changes its refractive index in response to the voltage. Waveguides and coupler made of silicon cause the two portions of a split light beam path to the column or it.
The light beams of the waveguide rain in each gap to electromagnetic surface waves, so-called surface plasmons. By fitting the plastic stress, the surface waves are modulated. The modulation is carried out in two different columns but coherent, since the same voltage is applied with different polarity. After passing through the column, the surface waves occur first as a modulated light beams into the output optical waveguides and are superimposed afterwards. The result is a beam of light in the strength of the digital information has been encoded.
Data traffic is growing exponentially
In the experiment, the MZM is reliable for the full spectrum of broadband fiber-optic networks by 1500 – 1600 nanometers in an electrical bandwidth of 70 GHz with data streams of up to 108 gigabits per second. The high modulation depth results from the high manufacturing precision silicon technology. The MZM can be produced with widespread CMOS process from microelectronics and thus easily integrated into current chip architectures.
At present in Germany are around 10 per cent of the current consumed by information and communication technologies, such as computers and smartphones with the user, but also through the servers in large data centers. Because traffic is growing exponentially, we need new approaches that increase the throughput and simultaneously attenuate the energy consumption. Plasmonic components could make a significant contribution here. (Nature Photonics, 2015; doi: 10.1038 / nphoton.2015.127)