The researchers at the lab of Qiang Lin, professor of electrical and computer engineering, used the lithium niobate (LN) bonded on a silicon dioxide layer to create not only the smallest LN modulator but one that also operates at high speed and is energy efficient.
The modulator is a key component of a photonics-based chip, controlling how light moves through its circuits. The device has a volume of just 0.58μm3 with a significant tuning efficiency up to 1.98GHz/V and a broad modulation bandwidth of 17.5GHz. The design achieve electro-optic switching at 11Gbit/s with a bit-switching energy of 22 fJ.
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,” said researcher 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,” says Lin. “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. 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,” said Lin.
The modulator could be used in conjunction with a nanocavity in creating a photonic chip at the nanoscale.
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