Spring 2018 Optical Connections Magazine



Counterintuitively, a silicon phonics proposal from Rockley Photonics, presented at Photonics West 2018, says that to optimise performance in optical communications device structures should be bigger rather than smaller. Matthew Peach attended.

A ndrew Rickman, CEO of Rockley Photonics, who has worked in silicon photonics for more than three decades, believes that industry’s expectation of smaller and smaller devices for optical communications is not the right approach to optimising manufacturability, eciency and performance. At January’s Photonics West conference in San Francisco, organised by SPIE, Dr Rickman gave a plenary talk explaining his provocative view, entitled Silicon Photonics: Bigger is Better. He explained, “Over the past 30 years silicon photonics has evolved into a volume technology supporting mainstream commercial applications. Though we have seen a proliferation of new approaches, the attributes required for commercial success remain

the same as they were three decades ago: volume manufacturability, optical power eciency, and high-signalling bandwidth. “Comparing to the evolution of the silicon microelectronics industry several decades earlier however, in the history of silicon photonics we see one key dierence: for electronic Integrated circuit design, reductions in process node geometry have generally always contributed to advancing the goals of the product, leading to a conclusion that smaller is better. In contrast, for silicon photonics, reducing process geometries have introduced complexities that can inversely impact manufacturability, optical power eciency and fibre-optic packaging. “As microelectronics races to progressively smaller nodes the industry faces a question: what makes for a leading photonics platform? Perhaps bigger is better.”

The convention with the majority of technological innovations is that new generations of OEM products and systems must be smaller, lighter and consume less energy than their predecessors. So why could developers possibly want a bigger component to do the same job than a smaller, older model? In fact, Dr Rickman not wowed by the silicon photonics devices developed so far, which are often integrated into transceivers for the communications market, but now finding other roles in other opto/electronic markets. Rickman believes that there is a structural problem in the approach of using semiconductor techniques to make optical devices. He told the Photonics West OPTO conference, “With microelectronics and CMOS, the industry generally wants to make things smaller but with photonics most of these structures need to be at least one


| ISSUE 12 | Q1 2018


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