Electro-optic Modulators For Specialised Applications

By Aaryaa Padhyegurjar

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The majority of current research into Electro-optic modulators is focused on applications on semiconductors or in fibre optic systems. But what about optical applications that aren’t wired or chip-based, such as vehicle distance sensing?

The modulator consists of a thin layer of an organic electro-optic material (green) deposited on top of a metasurface etched with sub-wavelength resonators integrated with microwave electronics (gold). (Credit: Capasso Lab/Harvard SEAS)

Researchers from Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a compact and tunable electro-optic modulator for free space applications that can modulate light at gigahertz speed in collaboration with researchers from the University of Washington’s Department of Chemistry.

“Our work is the first step toward a class of free-space electro-optic modulators that provide compact and efficient intensity modulation at gigahertz speed of free-space beams at telecom wavelengths,” said Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, senior author of the paper.

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To efficiently modify the intensity of light in free space, Capasso and his team created a high-speed modulator that combines metasurface resonators with high-performance organic electro-optical materials and high-frequency circuit architecture. The modulator is made up of a thin layer of organic electro-optic material placed on top of a metasurface etched with microwave circuitry and sub-wavelength resonators. The refractive index of the electro-optical material varies when a microwave field is applied to it, changing the intensity of light transmitted by the metasurface in nanoseconds.

“With this design, we now can modulate light 100 to 1,000 times faster than previously,” said Ileana-Cristina Benea-Chelmus, a research associate in the Capasso Lab and first author of the paper. “This speed advance opens new possibilities in computing or communications and the tunability of the metasurface opens up a vast application space for custom-tailored, ultracompact photonics that may in the future be deposited onto any nanoscale free-space optical product.”

The researchers now want to test if they can modulate light even faster and, by altering the architecture of the metasurface, adjust other properties of light like phase or polarisation.

Click here to access their entire study.


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