Cadmium sulfide nanowires can be used to create an all-optical photonic switch, a team at the University of Pennsylvania said. They combined the switch with others to create a logic gate for on-chip information processing. “Putting switches together lets you make logic gates, and assembling logic gates allows you to do computation,” said graduate student Brian Piccione. “We used these optical switches to construct a NAND gate, which is a fundamental building block of modern computer processing.” In creating the first such switch to be made of cadmium sulfide, the team, led by associate professor Ritesh Agarwal of the School of Engineering and Applied Science, built upon previous work showing that such nanowires are especially efficient at manipulating light. An all-optical photonic nanowire switch, the first to be made of cadmium sulfide, could help move the consumer electronics market into consumer photonics to overcome the imminent limitations of electronic integrated circuits. Here, laser light is emitted from the end of a cadmium sulfide nanowire. “The biggest challenge for photonic structures on the nanoscale is getting the light in, manipulating it once it’s there and then getting it out,” Agarwal said in a university release. “Our major innovation was how we solved the first problem, in that it allowed us to use the nanowires themselves for an on-chip light source.” Over the past few years, there has been a great deal of activity in nanophotonics to develop on-chip optical components, largely driven by the imminent limitations of electronic integrated circuits. Currently, nanoscale photonic circuits are bulkier and more energy-hungry than their electronic counterparts. To make their photonic switch, the researchers first precisely cut a gap into a nanowire. Then they pumped enough energy into the first nanowire segment that it began to emit laser light from its end and through the gap. Because they started with a single nanowire, the two segment ends were perfectly matched, allowing the second segment to efficiently absorb and transmit the light down its length. “Once we have the light in the second segment, we shine another light through the structure and turn off what is being transported through that wire. “That’s what makes it a switch,” Agarwal said. “We see a future where ‘consumer electronics’ become ‘consumer photonics,’ and this study shows that is possible,” he said. Postdoctoral fellows Chang-Hee Cho and Lambert van Vugt contributed to the study, which was published in Nature Nanotechnology (doi:10.1038/nnano.2012.144).