Huang and colleagues, including graduate student Jiayang Chen and senior research scientist Yong Meng Sua, dramatically boosted system efficiency by using a chip made from lithium niobate on insulator, a material that has a unique way of interacting with light. Unlike silicon, lithium niobate is difficult to chemically etch with common reactive gases. So, the Stevens’ team used an ion-milling tool, essentially a nanosandblaster, to etch a tiny racetrack about one-hundredth the width of a human hair.
Before defining the racetrack structure, the team needed to apply high-voltage electrical pulses to create carefully calibrated areas of alternating polarity, or periodic poling, that tailor the way photons move around the racetrack, increasing their probability of interacting with eachother.
Chen explained that to both etch the racetrack on the chip and tailor the way photons move around it, requires dozens of delicate nanofabrication steps, each requiring nanometer precision. “To the best of our knowledge, we’re among the first groups to master all of these nanofabrication steps to build this system—that’s the reason we could get this result first.”