Researchers develop all-optical photonic nanowire switch

11 September 2012

The research was conducted by associate professor Ritesh Agarwal and graduate student Brian Piccione of the Department of Materials Science and Engineering in the University of Pennsylvania’s School of Engineering and Applied Science. Post-doctoral fellows Chang-Hee Cho and Lambert van Vugt, also of the Materials Science Department, contributed to the study.

According to a statement, the research team’s innovation built upon its earlier research, which showed that the cadmium sulphide nanowires exhibited extremely strong light-matter coupling, making them efficient at light manipulation.

This quality is said to be crucial for the development of nanoscale photonic circuits, as existing mechanisms for controlling the flow of light are bulkier and require more energy than their electronic analogues.

‘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,’ said Agarwal. ‘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.’

The research team began by precisely cutting a gap into a nanowire. It then pumped enough energy into the first nanowire segment that it began to emit laser light from its end and through the gap.

Because the researchers 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,’ Agarwal said. ‘That’s what makes it a switch.’

The researchers were able to measure the intensity of the light coming out of the end of the second nanowire and to show that the switch could effectively represent the binary states used in logic devices.    

‘Putting switches together lets you make logic gates, and assembling logic gates allows you to do computation,’ Piccione said. ‘We used these optical switches to construct a NAND gate, which is a fundamental building block of modern computer processing.’

‘We see a future where “consumer electronics” become “consumer photonics”,’ Agarwal said. ‘And this study shows that is possible.’

The research, supported by the US Army Research Office and the National Institutes of Health’s New Innovator Award Program, was published in the journal Nature Nanotechnology.