When Yuankai Tang adjusted an electrical "knob" on a device narrower than a human hair is thick, light flickered to life—then dimmed, brightened, and vanished again, all under his precise control. The Emory University physicist had just demonstrated something that nobody had previously achieved: tuning light itself at the nanoscale with the flick of an electronic switch.
Tang and his mentor, Hayk Harutyunyan, a senior author and Emory professor of physics, have engineered what may be a turning point for technology that runs on light instead of electricity. Their breakthrough, published in the journal Optica, harnesses a quantum phenomenon called second harmonic generation—where two photons of the same frequency collide inside a material and merge into a single photon with twice the energy. It's a process already used in laser frequency-doubling and high-resolution medical microscopy, but never before at this scale, with this level of control.
The integrated component is a little more than 200 nanometers wide—more than 100 times smaller than the width of a human hair. Yet within it lies an active area just two to six nanometers wide, where light is generated: tens of times smaller than most existing devices for second harmonic generation, and far more controllable. "We can switch on our device, completely shut it off, and raise or lower its intensity within a range of 500%," Harutyunyan says. That tunability is the prize. For decades, engineers have miniaturized electronic transistors to build faster computers, but that progress plateaued roughly 15 years ago—transistors simply cannot shrink further and still function reliably. Light, by contrast, is blazing new frontiers. Fiber optics are gradually replacing copper wiring in data centers, and photonic chips that process light instead of electricity are beginning to emerge. But to make this technology work at scale, scientists need nanoscale light sources they can actually control.
The device Harutyunyan and Tang developed is a plasmonic electric-field-induced second harmonic generator—one that uses gold electrodes and an ultra-thin layer of lutetium oxide to create a "tunneling junction," a semi-permeable quantum barrier that lets electrons pass through while remaining stable under voltage. The challenge was formidable: the junction had to be sturdy enough to withstand electrical stress but thin enough to allow quantum particles to tunnel through. Tang first developed algorithms to model simulations of the design, then meticulously fabricated and tested devices at the atomic scale using specialized tools.
The result bridges electronics and photonics in a way that could remake how we transmit, process and sense information. Smaller, more efficient optical switches could speed up communications networks, enhance sensing capabilities, and even enable advances in quantum computing. Co-authors on the work include researchers from the University of Cambridge, the National University of Singapore, and the Air Force Research Laboratory at Eglin Air Force Base in Florida—a collaboration that speaks to the technology's broad potential.
As data demands explode and traditional electronics hit their limits, Harutyunyan's team has opened a new door. The future of information technology may well be written in light, controlled by nanoscale knobs that Tang and his colleagues have just learned to turn.