Skoltech scientists have developed an electro-optical modulator based on silicon photonics and plasmonics. The device allows controlling optical signals at ultra-small sizes – the active structure's length is only 3.6 micrometers. The development can be applied in optical communication systems, analog-to-digital conversion, and ultra-high-frequency signal processing.
The modulator is built on a silicon waveguide 7 micrometers wide and a special layer of indium tin oxide. The main feature is that several light beams (modes) propagate simultaneously in the waveguide. The output produces two signals, shifted in phase by 180 degrees relative to each other.
This design showed record efficiency: with direct current, signal attenuation reached 20.6 dB over a length of only 1.6 µm – that's 12.8 dB per micrometer. At high frequencies, the values are lower: 2.48 dB at 10 MHz and 1.25 dB at 1 GHz. The same modulator can operate in different modes: attenuate the signal, change its phase, or do both together.
The practical value of the development lies in creating ultra-compact photonic circuits. Usually, such tasks require an interferometer several millimeters long, but here everything fits into a few microns (thousands of times smaller). Plus, the modulator's characteristics can be adjusted after manufacturing.
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