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"... Two things made the breakthrough possible: the material ... and the way in which they used it. First, they chose a crystalline material known as lithium niobate, a combination of niobium, lithium, and oxygen that does not occur in nature but has, over the past 50 years, proven essential to the field of optics. The material is inherently nonlinear: ...
more recently, advances in nanofabrication techniques have enabled ... to create lithium niobate-based integrated photonic devices that allow for the confinement of light in a tiny space. The smaller the space, the greater the intensity of light with the same amount of power. ...
confined the light temporally. Essentially, they decreased the duration of light pulses, and used a specific design that would keep the pulses short as they propagate through the device, which resulted in each pulse having higher peak power.
The combined effect of these two tactics—the spatiotemporal confinement of light—is to substantially enhance the strength of nonlinearity for a given pulse energy ...
The net result is the creation of a nonlinear splitter in which the light pulses are routed to two different outputs based on their energies, which enables switching to occur in less than 50 femtoseconds ... By comparison, state-of-the-art electronic switches take tens of picoseconds ..."
From the abstract:
"Optical nonlinear functions are crucial for various applications in integrated photonics, including all-optical information processing, photonic neural networks and on-chip ultrafast light sources. ... Here we effectively utilize the strong and instantaneous quadratic nonlinearity of lithium niobate nanowaveguides for the realization of cavity-free all-optical switching. By simultaneous engineering of the dispersion and quasi-phase matching, we design and demonstrate a nonlinear splitter that can achieve ultralow switching energies down to 80 fJ, featuring a fastest switching time of ~46 fs and a lowest energy–time product of 3.7 × 10−27 J s in integrated photonics. Our results can enable on-chip ultrafast and energy-efficient all-optical information processing, computing systems and light sources."
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