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from the Brilliant! dept.

Photonics researchers report breakthrough in miniaturizing light-based chips [sciencedaily.com]:

But they're not yet small enough to compete in computing and other applications where electric circuits continue to reign.

Electrical engineers at the University of Rochester believe they've taken a major step in addressing the problem. Using a material widely adopted by photonics researchers, the Rochester team has created the smallest electro-optical modulator yet. The modulator is a key component of a photonics-based chip, controlling how light moves through its circuits.

In Nature Communications, the lab of Qiang Lin, professor of electrical and computer engineering, describes using a thin film of lithium niobate (LN) bonded on a silicon dioxide layer to create not only the smallest LN modulator yet, but also one that operates at high speed and is energy efficient.

This "paves a crucial foundation for realizing large-scale LN photonic integrated circuits that are of immense importance for broad applications in data communication, microwave photonics, and quantum photonics," writes lead author Mingxiao Li, a graduate student in Lin's lab.

Because of its outstanding electro-optic and nonlinear optic properties, lithium niobate has "become a workhorse material system for photonics research and development," Lin says. "However current LN photonic devices, made upon either bulk crystal or thin-film platform require large dimensions and are difficult to scale down in size, which limits the modulation efficiency, energy consumption, and the degree of circuit integration. A major challenge lies in making high-quality nanoscopic photonic structures with high precision."

The modulator project builds upon the lab's previous use of lithium niobate to create a photonic nanocavity -- another key component in photonic chips. At only about a micron in size, the nanocavity can tune wavelengths using only two to three photons at room temperature -- "the first time we know of that even two or three photons have been manipulated in this way at room temperatures," Lin says. That device was described in a paper in Optica.

The modulator could be used in conjunction with a nanocavity in creating a photonic chip at the nanoscale.

The project was supported with funding from the National Science Foundation, Defense Threat Reduction Agency, and Defense Advanced Research Projects Agency (DARPA); fabrication of the device was done in part at the Cornell NanoScale Facility.

Journal Reference:
Mingxiao Li, Jingwei Ling, Yang He, et al. Lithium niobate photonic-crystal electro-optic modulator [open], Nature Communications (DOI: 10.1038/s41467-020-17950-7 [doi.org])

Original Submission