The micrometre-sized electro-optical modulator could be used as a transducer in optical computing hardware such as optical artificial neural networks.
Electro-optical modulators in use today are typically between 1 millimeter and 1 centimeter in size. While silicon often serves as the passive structure on which photonic integrated circuits are built, the light matter interaction of silicon materials induces a rather weak optical index change, requiring a larger device footprint. While resonators could be used to boost this weak electro-optical effect, they narrow devices' optical operating range and incur high energy consumption from required heating elements.
By heterogeneously adding a thin material layer of indium tin oxide to the silicon photonic waveguide chip, the researchers led by associate professor of electrical and computer engineering Volker Sorger, have demonstrated an optical index change 1,000 times larger than silicon. Unlike many designs based on resonators, this spectrally-broadband device is stable against temperature changes and allows a single fiber-optic cable to carry multiple wavelengths of light, increasing the amount of data that can move through a system.
The findings were disclosed in a paper titled "Broadband Sub-λ GHz ITO Plasmonic Mach Zehnder Modulator on Silicon Photonics," published in the journal Optica.